INTRODUCTIONINTRODUCTION

Cervical cancer is the commonest gynecological malignancy in India.

Squamous cell carcinoma - 80%

Adenocarcinomas - 20%

INTRODUCTIONINTRODUCTION Carcinoma of the cervix metastasizes in

predictable sequential manner

The cervix drains into the para cervical L.N. and subsequently to the internal and external iliac nodes, including the obturator nodes.

The pelvic lymphatic drains into the common iliac and the para-aortic lymph nodes.

INTRODUCTIONINTRODUCTION Cervical cancers are clinically staged.

The FIGO staging system is the most widely used

The cornerstone of the system is a thorough careful pelvic examination, often done under general anesthesia.

Adjuncts to the pelvic examination include either an IVP or CT scan with IV contrast to determine whether there is ureteral obstruction and hydronephrosis.

Additionally, a chest X-ray is usually part of the initial workup.

FIGO STAGINGFIGO STAGINGCarcinoma-in-situ0

Spread to bladder or rectum and/or extending beyond true pelvis

IVA

Spread to lower third of the vaginaIIIA

Spread to pelvic side wallsIIIB

Spread to parametrium but not as far as lat. pelvic wall

IIB

Spread to distant sites outside true pelvis

IVB

Carcinoma involves upper 2/3rd of vagina

IIA

Clinically invasive carcinomaIB

Micro invasive carcinoma confined to cervix

IA

PRINCIPLE OF MANAGEMENTPRINCIPLE OF MANAGEMENT These are sq. cell ca. that are moderately sensitive

to radn. Hence radn plays an important role in management of carcinoma cervix.

Predictable pattern of spread helps in designing radn portals.

Since tolerance of Cx is very high hence high dose can be delivered.

Aim is to deliver curative dose of around Early stage - 80 - 85Gy to point A Advanced stage - 85-90Gy to point A

But this dose can’t be delivered by EBRT because of presence of dose limiting structures like bladder & rectum in the beam path.

Hence to achieve tumor control radn is delivered by combined technique of EBRT & Brachytherapy.

PRINCIPLE OF MANAGEMENTPRINCIPLE OF MANAGEMENT The cervical cancer has two components

Central component - Disease confined to cervix , vagina & medial parametria- best treated by brachytherapy

Peripheral component - Disease involving lateral parametria & lymph nodes-best treated by EBRT& brachytherapy as boost

PRINCIPLE OF MANAGEMENTPRINCIPLE OF MANAGEMENT Patients with stage IA ca cx are managed by

radical hysterectomy alone. If inoperable, then dose of approx.80 Gy is

delivered by brachytherapy alone Patients with stage IB may be managed by a

radical hysterectomy alone if the tumor is <4 cm in size with no other adverse features.

Stage IB with tumor > 4 cm, and all patients with stage IIA, IIB, IIIA, IIIB, and IVA are managed with EBRT with concurrent chemotherapy and Brachytherapy.

PRINCIPLE OF MANAGEMENTPRINCIPLE OF MANAGEMENT The relative proportion of EBRT increases with

increasing tumor bulk and stage Early stage - Brachytherapy is given simultaneously

or as sandwich with EBRT Advanced stage – EBRT is given prior to

Brachytherapy. This allows tumour shrinkage leads to a technically superior Brachytherapy

application and radiobiological advantage with better tumour

oxygenation and therefore more radio sensitivity as the tumour involutes.

Indications for EBRT prior to brachytherapy Bulky cervical lesions or tumors beyond stage IIA Exophytic, bleeding tumors; Tumors with necrosis or infection; or Parametrial involvement.

EBRTEBRT Parallel opposed AP/PA field i.e. two field

technique.

Four field box technique

Parallel opposed portals with midline shield when more dose is delivered by I/C BT

Parallel opposed portals AP/PA with pt. in Frog leg position in case of vaginal involvment. This position opens up skin folds in groin region

which is otherwise susceptible to skin reactions

TARGET VOLUMETARGET VOLUME

Principle is to treat primary tumour with the first echelon group of lymph nodes to maximize tumour control

Includes primary tumour Pelvic lymph nodes upto common iliac L.N.

( paracervical, parametrial, internal iliac, external iliac, presacral, sacral and the obturator L.N.)

& adequate margin for microscopic spread and set up uncertainties

POSITIONING & POSITIONING & IMMOBILIZATIONIMMOBILIZATION

Pt. is treated in supine position as it is most comfortable & reproducible position.

Pt. may be positioned using knee wedge to relaxes lower back making pt. more comfortable.

MANUAL MARKINGSMANUAL MARKINGS Anterior field centre is 3 cm above the pubic

tubercle Post field center is 5 cm above tip of coccyx

field size is either a square field of 15 x 15cm or rectangle of 14x16cm

lateral field centre is 8 cm above table top field size is 15 x 10cm

Radiographs should be taken to verify the field

SIMULATIONSIMULATION Pt. is given oral barium one hour prior to

simulation procedure to locate small bowel w.r.t. treatment portal.

Portals should be shaped to minimize small bowel within irradiated vol.

Pt. is made to lie supine on simulator couch with arms folded over chest.

A contrast enhanced vaginal cylinder is inserted in vagina & a rectal tube is inserted in rectum for later insertion of rectal contrast.

The ant. field is set while the position is viewed in fluoroscopy.

SIMULATIONSIMULATION Isocentric treatment is preferred & isocenter

is set at pt.’s middepth or at the vaginal marker.

Without moving couch/pt. gantry is turned 90° on either side.

While viewing in fluoroscopy ant. & post. margins of lateral fields are set by lowering or raising couch.

The superior & inferior margins remain same as that of ant. Portal.

Orthogonal radiographs are taken for later comparison with portal image/films.

RADIOLOGICAL MARKINGSRADIOLOGICAL MARKINGS Superior border –

At the L4-5 inter space to include external & internal iliac L.N.

This margin must be extended to the L3-4 inter space if common iliac nodal coverage is indicated.

Inferior border - at the inferior border of the obturator foramen. For vaginal involvement, lower

border is 2cm below the lower most extent of disease

tumours that involve lower third of vagina, inguinal nodes should be included in the fields

Lateral borders - 1.5 - 2cm margin on the widest portion of pelvic brim

RADIOLOGICAL MARKINGSRADIOLOGICAL MARKINGS Anterior margin - at

the pubic symphysis Posterior margin – at

S2 – S3 junction and it should extend to the sacral hollow in patients with advanced tumours

Superior & inferior margins - same as that for AP/PA Fields

SSD Vs SADSSD Vs SAD

SSD setupSSD setup Easy setup Setup time as

well as treatment time is more

Treatment time calculation done using PDD charts

SAD setupSAD setup Reproducible

setup

setup time & treatment time is less

TAR/TMR tables required for t/t calculation

TWO FIELD Heterogenous dose

distribution Parametrium under

dosed More skin reaction Useful when lower

part of vagina involved

FOUR FIELD Homogeneous box

shaped dose distribution

Whole target vol. including parametrium gets adequate dose

Skin reaction are decreased

Treatment time more

BEAM ENERGYBEAM ENERGY Because of the thickness of the

pelvis, high-energy photon beams (10 MV or higher) are especially suited for this treatment. They decrease the dose of radiation

delivered to the peripheral normal tissues (particularly bladder and rectum)

provide a more homogeneous dose distribution in the central pelvis.

avoid subcutaneous fibrosis

Composite of 6MV beam

6MV color wash

Composite of 15MV beam

15MV color wash

TIME DOSE & TIME DOSE & FRACTIONATIONFRACTIONATION

50Gy/25#/5wks with 2Gy/# In PGI

46Gy/23#/4.3wks ( 2Gy/#) More dose is delivered by I/C to achieve better

tumor control

MIDLINE SHIELDINGMIDLINE SHIELDING When more dose is delivered by

Brachytherapy then EBRT is delivered with the parallel opposed AP/PA ports (two fields) with midline shielding

Done to shield rectum & bladder. Shielding should be designed carefully to try

to achieve matching with the intracavitary dosimetry

Midline shielding can be rectangular or wedge shaped block.

PARAAROTIC L.N. PARAAROTIC L.N. IRRADIATIONIRRADIATION

For Para-aortic node involvement, pelvis & para-arotic L.N. should be treated as contiguous extended field with parallel opposed AP/PA fields.

Or the para - aortic L.N. and the pelvis are irradiated through separate portals

In this case, a gap calculation b/w the pelvic and para-aortic portals must be done to avoid overlap and excessive dose to the small intestines.

The upper margin of the field is at the T12 - L1 interspace and the lower margin at L4 – L5 while width of field is set to include transverse processes of spine.

An IVU should be done to delineate kidneys

PARAMETRIAL BOOSTPARAMETRIAL BOOST

If parametrial tumor persists after delivery of 50 -60Gy is then boost dose of 10 Gy/5#s may be delivered with reduced AP/PA portals with superior border at mid SI joint.

The central shield should be used to shield the bladder and rectum.

ROLE OF 3-D CRT & IMRTROLE OF 3-D CRT & IMRT Ensures better tumor control. Lesser dose to normal tissue

resulting in less late term complications.

Potential reduction in acute toxicity & better radiation tolerance.

PALLIATIVE RTPALLIATIVE RT Pt . of stage 4B or recurrent carcinoma require

palliation Aim is to relieve pt. from pain & bleeding For vaginal bleeding single I/C insertion is given

delivering a dose of 6000mgh( 55Gy to point A) If pt. has previously received radn then prescribed dose

is lower(4000 -5000mgh) EBRT may be delivered by two field or four field

technique 26Gy in 13#s Or single dose of 8-10 Gy that can be repeated

seeing response at an interval of 3-4wks

BRACHYTHERAPYBRACHYTHERAPY Brachytherapy is a type of radiation treatment

in which small, encapsulated radioactive sources are arranged in a geometric fashion in & around tumour

ADV. It delivers very high dose of radiation to tumor Sparing normal tissue Dose delivered in short duration.

TYPES OF BTTYPES OF BT Depending on methods of source loading :

Pre loading : The applicator is preloaded and contains radioactive sources at the time of placement into the patient

After loading : The applicator is placed first into the target position and the radioactive sources are loaded later, either

manual after loading or remote after loading

TYPES OF BTTYPES OF BT Depending on dose rate there are four types

of delivery modes of I/C Brachytherapy Low Dose Rate (LDR) : 0.4–2 Gy /hr Medium Dose Rate (MDR) :2-12Gy/hr High Dose Rate (HDR) : >12Gy/hr Pulsed Dose Rate (PDR) : pulses of around

1Gy/hr

BRACHYTHERAPYBRACHYTHERAPY Brachytherapy plays vital role in treatment

of ca cx. & is mainly applied as an intracavitary procedure in selected cases complemented by interstitial implants.

It consists of positioning specially designed applicators bearing sealed radioactive sources into a body cavity in close proximity to the target tissue.

I/C applications are temporary that are left in the patient for a specified time to deliver prescribed dose.

WHY I/C BRACHYTHERAPYWHY I/C BRACHYTHERAPY Uterine cx. is ideally suited for I/C brachy

therapy because

High tolerance of cervix ,uterus & vagina It is accessible organ hence Brachytherapy can

be practised with ease. The endocervical canal & vaginal vault form a

suitable vehicle to carry rigid applicators with radioactive sources.

These applicators can be used with minor modifications in all pts.

ADV. OF I/C ADV. OF I/C BRACHYTHERAPYBRACHYTHERAPY

High dose of radiation is delivered in shortest time. Cervix receives 20,000 – 25000 cGys. Uterus receives 20,000- 30000 cGys Vagina receives 10,000 cGys.

such high doses can’t be delivered by any technique of EBRT.

Best long term control is achieved Sharp Fall off of dose and hence less dose to the

normal structure. Less late radiation morbidity . Preservation of normal anatomy. Better sexual functional life.

HISTORYHISTORY1898 : Discovery of Radium by Marie Curie in

Paris.

1903 : Margaret Cleaves, a New York physician described inserting Radium into the Uterine cavity of a patient with Ca Cervix.

1908 : I/C brachytherapy started in Vienna

1910 : I/C brachytherapy started in Stockholm1912 : I/C brachytherapy started at Paris. 1930 : Todd & Meredith developed Manchester

system in U.K.

DOSIMETRIC SYSTEMSDOSIMETRIC SYSTEMS The historical dosimetric systems were

developed when computer treatment planning and dose computations were not available

Term ‘system’ specifies a set of rules for Geometrical arrangement of a specific set of radio

isotopes in a specialised applicator To obtain suitable dose distributions over the

volume to be treated. It specifies treatment in terms of the dose, time

and administration A specified set of tables to allow, reproducible and

easy calculation in most of the encountered clinical scenarios.

A system ensures safety and is based on clinical experience.

STOCKHOLM SYSTEMSTOCKHOLM SYSTEM Fractionated (2-3 #s) course over a period of

one month. For a period of 22 hours each. Separated by 1-3wks This system used

Intravaginal boxes made up of silver or gold The intrauterine tube made up of flexible rubber. These were not fixed together

Unequal loading of Radium 30 to 90 mg of Radium was placed inside the uterus While 60 - 80 mg were placed inside the vagina.

A total dose of 6500 -7100 mg -hrs was prescribed out of which 4500 mg Ra was contributed by the vaginal box. (dose rate-110R/hr)

PARIS SYSTEMPARIS SYSTEM Single application of Radium for 120hrs

(5-6days) In this system, almost an equal amount

of Radium was used in the uterus and the vagina.

The system incorporated two cork colpostats (cylinder) with

13.3mg Radium in each and an intrauterine tube of silk rubber with

33.3mg Radium The intrauterine sources contained three

radioactive sources, with source strengths in the ratio of 1:1:0.5.

the colpostats contained sources with the same strength as the topmost uterine source

Designed to deliver a dose of 7000 - 8000 mg hrs over a period of 5days (45R/hr) (5500mg/hr)

DOSE SPECIFICATIONDOSE SPECIFICATION Done in mg-hr i.e. simple mathematical product

of mg of Radium times the duration (in hours) of the implant.

It was easy to use. The dose prescription was entirely empirical due

to the lack of knowledge about the biological effects of radiation

on the normal tissues and the tumor understanding about the dose, dose distribution and

the duration of treatment. Only applicable when both tandem & ovoids are

used & sources are loaded in a rigidly prescribed manner.

FALLACIESFALLACIES Long treatment time, discomfort to the patient Dose prescription method was empirical. Both

systems specified dose in mg-hour. Does not give any information about dose

distribution. When used in conjunction with EBRT, overall

radiation treatment can’t be adequately defined Dose specification method lacks the information on

Source arrangement Position of tandem relative to the ovoids Packing of the applicators Tumour size, and Patient anatomy.

With the use of this dose prescription method dose to important anatomical targets could not be quantified adequately.

Ignored the importance of tolerance of different critical organs to radiation.

MANCHESTER SYSTEMMANCHESTER SYSTEM

The Manchester system is one of the oldest & extensively used systems in the world.

Developed by Todd & Meredith in 1930 & was in clinical use by 1932.

This system was initially developed for radium tubes, but was easily adapted to different afterloading systems.

MANCHESTER SYSTEMMANCHESTER SYSTEM Manchester system was based on following principles: To define the treatment in terms of dose to a point. To

be acceptable this point should have following criteria : It should be anatomically comparable from patient to patient. Should be in a region where the dosage is not highly sensitive

to small alteration in applicator position. Should be in position that allows correlation of dose with

clinical effects To design a set of applicators and their loading (with a

given amount of radium), which would give the same dose rate irrespective of the combination of applicators used.

To formulate a set of rules regarding the activity, relationship & positioning of the radium sources in the tandem & vaginal ovoids to achieve desired dose rate.

POINT APOINT A Todd & Meredith defined a point in

paracervical triangle where the uterine vessels cross the ureter as point A.

Point A is defined as a point 2cm. lateral to the center of the uterine canal and 2 cm. superior to the mucosa of the lateral fornix, in the plane of the uterus.

Now point A is defined as a point 2cm above the distal end of lowest source in cervical canal & 2cm lat. to centre of tandem.

Dose at point A showed a correlation with local control and the incidence of late normal tissue toxicity in the pelvis

POINT BPOINT B

Point B is defined 2cm above external os & 5 cm laterally to midline

Represents dose to the pelvic wall, obturator L.N.

The dose at point B is approx. 25 -30% of the dose at point A.

Dose to point B, depends little on the geometric distribution of radium, but on the total amount of radium used

DOSE LIMITING STRUCTURESDOSE LIMITING STRUCTURES

Bladder Rectum Vaginal mucosa Rectovaginal septum

No more than 40% of total dose at point A could be delivered safely through the vaginal mucosa.

The rectal dose should be 80% or less of the dose at point A; this rectal dose can usually be achieved by careful packing.

APPICATOR IN MANCHESTER APPICATOR IN MANCHESTER SYSTEMSYSTEM

Similar to that used in Paris system It had a pair of ovoids & a

intrauterine tube

INTRAUTERINE TUBEINTRAUTERINE TUBE The intrauterine tube was made up of the thin rubber

( to prevent excessive dilatation of the cervical canal) These tubes were available in three separate lengths

2cm

4cm

6cm

in order to accommodate 1, 2 or three Radium tubes (2

cm long) in line. I.U.tubes were closed at one end, and had a flange at

the other end so that when packed into position, the uterine tube did not slip out during the treatment.

OVOIDSOVOIDS Used in pairs, one in each lateral fornix The shape of ovoids mimics the shape of

isodose curves around a Radium tube having "active length" of 1.5 cm.

The ovoids were designed to be adaptable to the different vaginal capacity, with diameter of 2 cm 2.5 cm 3 cm

The largest ovoid are placed in the roomiest vagina in order to achieve the best lateral dose throw off

SPACERSSPACERS Apart from ovoids & I.U.tubes spacers or washers

were used

To maintain the distance between the ovoids

To help in their fixation

Spacer was used to give the largest possible separation b/w the ovoids so that the dose could be carried out as far laterally as possible.

It maintained a distance of 1cm b/w the ovoids The washer was only used when it was not possible

to accommodate the spacer.

PACKINGPACKING

Manchester applicators do not incorporate rectal shielding.

Hence gauze is packed firmly and carefully behind the ovoids, anteriorly b/w the ovoids and the base of the bladder, and around the applicator tubes down to the level of the

introitus The amount of packing should be such that at

least 1.5 cm separation is achieved b/w ovoids and vaginal mucosa.

Packing helps to keep the applicators in position to reduce dose to bladder and anterior rectal wall.

RULESRULES The point A should receive the same dose rate,

irrespective of the combination of applicators used. Not more than one third of the total dose to point A

should be delivered by the vaginal ovoids. So that tolerance of vagina mucosa is not exceeded

Standard or ideal loading is 60-40 i.e. 60% of the dose to point A is contributed by intrauterine sources while 40% is contributed by ovoids.

Total Dose to point A : 8000 R Total number of applications : 2 Total time for each application : 72 hrs Total time : 144 hrs Dose rate desired : 55.5 R /hour to point A

Amount of radium to be used was defined in terms of units.

1 unit = 2.5 mg of radium filtered by 1 mm platinum. The loadings were specified in terms of integral

multiples of this unit.

LOADING PATTERNLOADING PATTERN

Tube Type

Length

Tubes used

Mg Ra loaded

Units loaded from fundus

to cervix

Tubes (mg)

used for loading

Large 6 3 35 6-4-4 15-10-10

Medium

4 2 25 6-4 15-10

Small 2 1 20 8(10) 20OvoidTubes used

Mg Ra loaded

Units loaded

Tubes (mg) used for loading

Large 3 22.5 9 10-10-5 or 20/25*

Medium 2 20 8 20

Small 1 17.5 7 10-5-5 or 20/15**

LOADING PATTERNLOADING PATTERN Total dose at point A using different

combinations of I.U tube & ovoids : Large tube with large ovoid and washer : 57.5 R Large tube with large ovoid and spacer: 56.9 R Large tube with small ovoid and washer: 57.6 R Medium tube with small ovoids and spacer: 57.3

R The variations were thus within 1.5% range.

ICRU SYSTEMICRU SYSTEM For reliable and relevant comparison of

different methods and their clinical results ICRU38 recommends a common terminology for prescribing recording and reporting I/C Brachytherapy applications.

The ICRU recommends a system of dose specification that relates the dose distribution to the target volume, instead of the dose to a specific point

The dose is prescribed as the value of an isodose surface that just surrounds the target volume.

ICRU REPORTINGICRU REPORTING Description of technique

Time dose pattern (application duration)

Description of reference volume

Dose at reference points

Description of the Description of the TechniqueTechnique

Minimum information should include the orthogonal radiographs of the application. Source used (radionuclide, reference air kerma

rate, shape and size of source, and filtration) applicator type Loading pattern Simulation of linear source for point or moving

sources Applicator geometry (rigidity, tandem curvature,

vaginal uterine connection, source geometry, shielding material)

Total reference air Kerma - proposed to introduce international units into the Brachytherapy reporting.

DOSE AT REFERENCE POINTSDOSE AT REFERENCE POINTS

The dose to bladder and rectum depends on the distribution of sources in a given application.

The maximum dose to bladder and rectum should be less than 80% of the dose to point A

The localization of bladder and rectum can be performed using radiographs taken with contrast media in the bladder and rectum.

BLADDER POINTBLADDER POINT

ICRU recommends : On a lat. radiograph

reporting dose at a point at posterior surface of Foley balloon on AP line through centre of balloon.

On AP radiograph, reference point is taken at the centre of the balloon

RECTAL POINTRECTAL POINT The dose is calculated at

a point 5 mm posterior to (opacified) vaginal cavity along an AP line midway between vaginal sources.

On the frontal radiograph, this reference point is taken at the intersection of (the lower end of) the intrauterine source through the plane of the vaginal sources.

LYMPHATIC TRAPEZOIDLYMPHATIC TRAPEZOID Lymphatic trapezoid

represents dose at lower Para-aortic , common and external iliac L.N.

A line is drawn from S1-S2 junction to top of symphysis, then a line is drawn from middle of this line to middle of ant. aspect of L4,

A trapezoid is constructed in a plane passing through transverse line in pelvic brim plane and midpoint of ant. aspect of body of L4

PELVIC WALL REFERENCE PELVIC WALL REFERENCE POINTSPOINTS

The pelvic wall reference point, represents absorbed dose at the distal part of the parametrium and at the obturator L.N.

Reporting dose at reference points related to well defined bony structures & L.N. areas is particularly useful when I/C BT is combined with EBRT

On a AP radiograph, pelvic-wall reference point is located at intersection of following lines a horizontal line tangential to the

highest point of the acetabulum, a vertical line tangential to the

inner aspect of the acetabulum. On a lat. radiograph, the highest

points of the right & left acetabulum, in cranio -caudal direction, are joined & lateral projection of the pelvic-wall reference point is located mid-way b/w these points.

REFERENCE VOLUMEREFERENCE VOLUME The reference volume is the

volume encompassed by the reference isodose, selected and specified to compare treatments performed in different centres using different techniques.

ICRU (43) recommends reference volume be taken as the 60-Gy isodose surface, resulting from the addition of dose contributions from any external-beam whole-pelvis irradiation and all I/C insertions. Height h, Width w, and Thickness t. and their product should be

reported separately

TREATED VOLUMETREATED VOLUME

The Treated Volume is the pear and banana shape volume that received (at least) the dose selected and specified by the radiation oncologist to achieve the purpose of the treatment e.g. tumour eradication or palliation, within the limits of acceptable complications

IRRADIATED VOLUMEIRRADIATED VOLUME

The irradiated volume is the volume, surrounding the treated volume, encompassed by a lower isodose to be specified, e.g., 90 – 50% of the dose defining the treated volume.

Reporting irradiated volumes is useful for interpretation of side effects outside the treated volume and for purpose of comparison.

APPLICATORSAPPLICATORS Applicators are small-caliber tubes that are

inserted into body cavities to hold the brachytherapy sources in clinically defined configurations, or loading patterns.

The applicators include A tandem to be inserted into the uterus

with different lengths that allow for adaptation according to the individual anatomy (with a fixed uterine flange)

and angled at varying degrees to the line of the vaginal component (0°,15°,30°,45° )

The deliberate angle in the tube draws the uterus, in most patients, into a central position in the pelvis away from the pouch of Douglas, the sigmoid colon, and the anterior rectal wall.

Two ovoids, to be positioned in the vaginal vault abutting the cervix.

APPLICATORSAPPLICATORS Applicators used to insert

intracavitary sources in the uterus and vagina included Rubber catheters and ovoids developed

by French researchers, Metallic tandems and plaques designed

in Sweden Thin rubber tandems and ovoids of the

Manchester system. Fletcher (1953) designed a preloadable

colpostat, which Suit et al. (1963) modified and made after loading

APPLICATORSAPPLICATORS IDEAL CHARACTERISTICS of applicators

It should have a fixed geometry. It should be made of rigid material as fixed & rigid

applicators attain and hold better geometry of the insertions Lightweight (ideally 50- 60gm but should not be more than

100gm) for the patient's comfort capable of easy sterilization. Applicators should be of inert material that is not adversely

affected by exposure to gamma radiation. There should be minimal attenuation of gamma rays by the

walls of the applicators i.e. it should not produce its own characteristic radiations

Vaginal ovoids should be perpendicular to the long axis of vagina to avoid more dose to rectum and bladder.

I.U. tube should be angulated

FLATCHER APPICATORFLATCHER APPICATOR Based on Manchester

System Stainless steel Cylindrical ovoid Bladder and rectal shields Preloaded but modified by

Suit for afterloaing Disadv.

Presence of shielding lead to uncertainty in dosimetry.

Cylindrical caps lead to nonuniform doses to vaginal mucosa.

Fletcher - Suit- Delclosapplicator for afterloading with Ir-192

HENSCHKE APPLICATORHENSCHKE APPLICATOR Ovoids are

hemispherical in shape. Three ovoid diameters

& various tandem lengths are available

The radioactive sources are placed parallel to the long axis of the bladder & rectum

Thus delivering a higher dose to these organs

PGI APPLICATORPGI APPLICATOR Fixed geometry applicator Desired dose can be

delivered around area of interest

Easy & accurate dosimetry Less rectal dose because

of obtuse angle. Perineal plate which helps

to maintain fixed geometry of application i.e. applicator remains in fixed position

Disadv. Bladder complications are

more as it receives higher dose due to more angulation

MDR/HDR APPLICATORMDR/HDR APPLICATOR Modern after loading

applicator that mimics classical Manchester based applicator.

I.U. tube with different lengths graduated in centimeters (4& 6cm) & angled at 40° to the line on the vaginal component of the tube.

The vaginal ovoids are of ellipsoid shape (large, medium, small, half)

These tubes are held together and their relative positions fixed by a clamp ensuring an ideal physical arrangement.

Used for HDR( with small tube diameter)

MOULDED APPLICATORMOULDED APPLICATOR

The molded applicators represent the most individualized approach of treatment

RING APPLICATORRING APPLICATOR Based on Stockholm technique Intrauterine tubes are of

different lengths & angulations Ring is available in different

diameters (26, 30, 34mm) Acrylic caps cover the ring tube

to reduce dose to vaginal mucosa.

The ring and the intrauterine tube are fixed to each other with a screw.

A rectal retractor helps in pushing rectum so that it receives less dose.

Adv. of ring applicator: Fixed geometry Interrelationship b/w ovoids is

maintained. Customized planning can be

done

IDEAL APPLICATIONIDEAL APPLICATION Use longest tandem that the

patient's anatomy can accommodate.

Increasing the tandem length increases the point B (lateral parametrium and pelvic lymph nodes) contribution relative to the uterine cavity surface dose

The radioactivity near the ends of the long tandem contributes little to the surface dose (because of inverse-square law), whereas each tandem segment makes roughly equal contributions to points remote from the applicator.

IDEAL APPLICATIONIDEAL APPLICATION Colpostats /ovoids with largest clinically

indicated dia. should be used to deliver highest tumor dose at depth, for a given mucosal dose.

As colpostat diameter increases from 2 to 3 cm, the vaginal surface dose decreases by 35% relative to the dose 2 cm from the applicator surface; This is simply a consequence of increasing the source-to-surface distance.

The geometry of the insertion must prevent under dosing around the cervix;

Sufficient dose must be delivered to the Para cervical areas; and

Tolerance of vaginal mucosa, bladder and rectum must be respected.

IDEAL APPLICATIONIDEAL APPLICATION

Tandem -1/3 of the way b/w S1 –S2 and the symphysis pubis

The tandem -midway b/w the bladder and S1 -S2

Marker seeds should be placed in the cervix

Ovoids should be against the cervix (marker seeds)

Tandem should bisect the ovoids

The bladder and rectum should be packed away from the implant

IDEAL APPLICATIONIDEAL APPLICATION The tandem should be in the

midline or as nearly as possible equidistant from the lateral pelvic wall

The vaginal colpostats should be symmetrically positioned against the cervix in relation to the tandem

The ovoids should fill the vaginal fornices, add caps to increase the size of the ovoids if necessary.

The ovoids should be separated by 0.5 –1.0 cm, admitting the flange on the tandem.

The axis of the tandem should be central between the ovoids.

Computerized dose optimization cannot make up for a poor applicator position.

PATIENT PREPARATIONPATIENT PREPARATION

Pt is Pt is anaesthesitized.anaesthesitized.

Patient is in Patient is in lithotomy positionlithotomy position

Perineal area is Perineal area is disinfecteddisinfected

APPLICATOR CHECKAPPLICATOR CHECK

Applicator set is Applicator set is check for integrity check for integrity and completenessand completeness

Length of uterus is Length of uterus is measuredmeasured

Dilatation of the Dilatation of the cervix with cervix with standard tooling.standard tooling.

PROCEDUREPROCEDURE Correct length of IU-tube &

ovoids are selected Inserted one by one and

attached to fixing mechanism.

To determine the rectal wall on CT or radiograph a radio opaque marker is inserted

After insertion of applicator gauze packing is done behind the ovoids to push rectum and bladder away reducing the dose to these organs

After procedure orthogonal After procedure orthogonal radiographs are taken to check radiographs are taken to check applicator geometry.applicator geometry.

IMAGINGIMAGING For treatment planning

purposes orthogonal radiographs/CT images are taken

Images are transferred to Treatment planning system.

If radiographs are to be used for planning then radiographs are scanned to transfer images to TPS.

Catheter reconstruction done on TPS

DOSE PRESCRIPTIONDOSE PRESCRIPTION

DOSE EVALUATIONDOSE EVALUATION

DOSE RATE EFFECTDOSE RATE EFFECT Dose rate is one of the

important factor that determines biological consequences of a given absorbed dose

As the dose rate is lowered & exposure time extended, the biological effect of a given dose is generally reduced.

Continuous low dose-rate (CLDR) irradiation may be considered to be an infinite number of infinitely small dose fractions

consequently, the survival curve for continuous LDR becomes shallow & shoulder tends to disappear i.e. survival curve becomes exponential function of dose .

RATIONALE FOR LDR RATIONALE FOR LDR BACHTHERAPYBACHTHERAPY For any selected dose,

increasing the dose rate will increase late effects much more than it will increase tumor control.

Conversely, decreasing the dose rate will decrease late effects much more than it will decrease tumor control.

Thus the therapeutic ratio (ratio of tumor control to complications) increases as the dose rate decreases.

For higher dose rates, the dose reduction needed to match the late effects is larger than the dose reduction needed to match tumor control.

Despite all these facts there is a trend towards increased use of HDR BT

In I/C BT equivalent HDR regimens can be achieved without loss of therapeutic ratio.

Because the radn dose that produces unwanted late effects is significantly less than treatment dose (75% of prescribed dose)

As OAR( rectum & bladder) are some distance away from Brachytherapy sources.

Corrections LDR – MDR - 33% reduction HDR – HDR - 50% reduction

LDR BRACHYTHERAPYLDR BRACHYTHERAPY

The only type of brachytherapy possible with manual after loading.

Most clinical experience available for LDR brachytherapy

Earlier Radium was used for Low dose rate brachytherapy

Performed with remote after loaders using 137Cs or with manual after loading source trains of 137Cs pallets.

ADV. OF LDRADV. OF LDR Long history of use Ability to predict rate of late complications Radio biologically superior as

Improves chances of catching tumors in sensitive phase of cell cycle

Favorable dose-rate effect on repair of normal tissues

Infrequent replacement and calibration of sources because of long isotope half-life

MDRMDR

Used to have adv of both LDR & HDR

Since dose rate correction was not used so it lead to lot of complication

However in PGI two consecutive studies led to incorporation of a 33% dose rate reduction-probably only reported clinical data with use of MDR

Availability of microselectron HDR with miniature Ir-192 source & resultant smaller applicators with the attendant adv of better packing lead to more wide spread adoption of HDR.

HDR BRACHYTHERAPYHDR BRACHYTHERAPY Practiced only with remote after

loading. Most modern brachytherapy is

delivered using HDR Outpatient procedure Optimization possible

In the past Co – 60 pellets were used

Today, virtually all HDR brachytherapy is delivered using single miniature linear 192-Ir stepping source

Source moves step by step through the applicator

The dwell times in different locations determine the dose distribution

HDRHDR During a treatment, the source is driven out

of the HDR unit, remotely. Source steps through pre-determined

treatment/dwell positions within each treatment catheter,

Stopping at each dwell position for a pre-calculated length of time i.e. dwell time,

to deliver the planned treatment dose distribution.

This type of stepping source HDR unit helps to achieve optimized dose distribution for the treatment.

ADV. OF HDRADV. OF HDR

Out patient procedure Pt.is not confined to bed for hours or days during

irradiation No indwelling catheters or vaginal packing Geometry easily maintained during treatment Ability to treat greater patient loads (high output

of patients on each machine) Optimization of dose distribution by altering the

dwell times of the source at different locations

PDR BRACHYTHERAPYPDR BRACHYTHERAPY PDR technology was developed at the

beginning of the 90's Unit has a similar design as HDR, however the

activity is smaller (around 1Ci instead of 10Ci) Stepping source operation - same

optimization possible as in HDR Treatment over same time as LDR treatment The biologic effect mimics LDR, and the

dose optimization mimics HDR. In-patient treatment: hospitalization required Source steps out for about 10 minutes per

hour and then retracts. Repeats this every hour to deliver mini fractions (‘pulses’) of about 1Gy

PDRPDR Advantages

Complication rate profile more similar to that of LDR

Between fractions, patient is not radioactive, allowing for near continuous nursing care during treatment

Radiation protection

Disadvantages Long term results not available

VAULT RTVAULT RT Disease localized to upper part of the

vault measuring <0.5cm in thickness & no vaginal wall involvement

Delivered with colpostats

INTERSTITIAL INTERSTITIAL IMPLANTATIONIMPLANTATION

The aim of this technique is to tailor the dose of irradiation to the anatomy of the patient with a better target volume coverage.

Originally, interstitial implants were performed with free-hand placement of the radioactive needles.

The development of transperineal or transvaginal templates resulted in a better needle positioning.

INTERSTITIAL INTERSTITIAL IMPLANTATIONIMPLANTATION

Indications : Pt. of ca cx with

Distorted anatomy Narrow vagina & obliterated fornices When os / uterine canal can’t be identified.

Extensive paravaginal (>0.5cm) or distal vaginal involvement

when parametrial extent of the tumor cannot be encompassed by standard intracavitary brachytherapy.

patients with a recurrence inside an area previously irradiated restricting the use of further external irradiation

Post op vault recurrence

INTERSTITIAL INTERSTITIAL IMPLANTATIONIMPLANTATION

It is delivered with either Along with ICA

using ring applicator that has provision for implantation

using template e.g. MUPIT

SEQUELAESEQUELAE Acute reactions:

Diarrhoea , Nausea , abdominal cramping, rectal discomfort, & occasionally rectal bleeding Fatigue ,weakness ,

Dysuria, frequency, nocturia Erythema and dry or moist desquamation may

develop in the perineum or intergluteal fold. Late reactions:

Haemorrhage, rectal ulceration ,rectovaginal fistulae, rectal strictures,proctitis

Small bowel obstruction or perforation Vesicovaginal fistulae,cystitis

CONCLUSIONCONCLUSION Radiation plays an important role in management

of carcinoma cervix both in the form of EBRT & Brachytherapy & is only mode of treatment in advanced cases.

Both of the components are important; however, successful outcome of treatment depends on skilled use of I/C Brachytherapy

Traditional method of low dose rate I/C Brachytheapy is being replaced by modern high dose rate Brachytherapy

Most of clinical experience is available with low dose rate Brachytherapy

Comparison of modern Brachytherary is still done with clinical results of low dose rate Brachytherapy.