Clinical applications of SBRT: Lung, Liver, PancreasMaryLou DeMarco, MS, CMD

Susan Leuthold, CMD

Over1000 SBRT Lung Patients

Planned at Moffitt

Lung: Sim and Immobilization

Gantry Collision Check

Contours: PTV/GITV

Contours: RINGS

RING100 RING

RINGRING100

Boarding Pass: Constraints

Case Study: Lung SBRT, Previous Tx

Previous Tx Right On New PTV

Make Contours Out Of Previous Tx Isodose Lines

OARs

Lungs: Minus GITV

Challenge: Chestwall Dose

PTV_edit

PTV_edit

Chestwall_R: 3cm up and down

RING_100

RING

2 Arc Beams

Prescription: 1000 x 5 = 5000cGy

Optimizer: First Ring

First Isodose Rings that we get

The Rest Of The Rings: 6

Rings Into Optimizer With EUD @0.6

Rings to Max DVH & 0.09

Isodose Lines Pull In

Make Ring of 50% Line

The 50% line in Optimizer: EUD

The 50% Line In Optimizer: Max DVH

Gradient Index: RTOG

549.1 / 201.1 = 2.7From RTOG: a 201.1cc PTV needs a Dose Gradient

< 3.3, so the Dose Gradient is good

OARs

Previous Tx Areas Into Optimizer

Isodose Lines

Graded Plan Into Mosaiq

SBRT of the Pancreas and Liver

Susan Leuthold, CMD

Dosimetry at MCC…

• Specializing • Primary and secondary services• GI and Sarcoma • Esop, panc, gastric, adrenal, liver, gb, rectal,

anal• Sim and treat (palliative)• 3D, IMRT, SRT, SBRT, HDR, LDR, Intra-op• My Team

Advantages of SBRT

• Shorter treatment course– Less scheduling conflicts– Less driving, lodging– More likely to complete tx

• As effective (increase dose and local control)• Ease of planning

• Overview of pancreas cancer• Definition of borderline resectable• Treatment technique

– SBRT (3D gated) also use IMRT/VMAT

• Then on to Liver (3D gated Vs. IMRT)

The Pancreas

What does the pancreas do?

• Hormone production (endocrine)– Insulin – decrease glucose– Glucagon – increase glucose– Somatostatin – regulate insulin/glucagon

production• Digestion (exocrine)

– Break down protein, carbohydrates, and fat– Neutralize acid from stomach

Pancreas Cancer

• 9th most common cancer but 4th most common cause of cancer death in U.S.

• ~50,000 new diagnoses per year• Most present at advanced stage• 15 – 20% resectable at diagnosis• R0 resection offers chance for cure

Pancreas Cancer

• Most present at advanced stage• Clinical presentation

– Jaundice– Weight loss– Diabetes– Abdominal pain– Pruritus (itchy sensation)– Steatorrhea (excess fat in stool)

Pancreas Cancer

• Prognosis is grim– Long-term survival for all patients 3 – 4%, 5 yr– If have surgery 5 yr survival to 20% – “systemic disease”

• Median survival– After resection: 12 – 26 months– Locally advanced: 9 – 13 months– Metastatic: 3 – 6 months

Definitions

• Resectable• Locally advanced – non-resectable• Borderline resectable• Resection classification

Borderline ResectableDefinition

1. ≤180° circumferential tumor abutment of portal vein (PV), superior mesenteric vein (SMV), or superior mesenteric artery (SMA)

2. Short segment (1.5 cm) encasement of PV or SMV amenable to partial resection and reconstruction

3. Gastroduodenal artery encasement to origin of hepatic artery

Resectable

SMV

Locally advanced/unresectable

SMA

Tumor

Borderline-resectable

SMV

Tumor

Margin definitions

• Negative margins– R0

• Microscopically positive margins– R1

• Grossly positive margins– R2

Goal of treatment

• Complete surgical removal of the tumor

• With no cancer at the edges of the specimen

Our approach

Chemo (GTX) over 9 weeks -Gemcitabine (IV infusion)

-Taxotere (IV infusion)-Xeloda (oral)

• Then SBRT for 5 days • Re-eval for poss resection

Re-evaluation 3-4 weeks after

• Restaging PET/CT

• Tumor board presentation to see if lesion has shrunk away from blood vessel enough for surgeon to attempt resection

SBRT planning• Tumor localization

– Find tumor location accurately for each fraction.• Patient simulation

– Modified simulation for SBRT• SBRT planning (3d gated or IMRT)

– In this case, we create a set of beam angles and portals that deliver the treatment & the boost simultaneously –Dose painting

– Gated if a lot of motion

Prior to Simulation

• Patient undergoes implantation of fiducial markers– Done via Endoscopic ultrasound (EUS)– Place 3-4 gold fiducials into the tumor itself– Fiducial markers will be useful for target

delineation and for daily image guidance

Fiducial markers

Motion

• Fluoro-sim before CT sim• Short term solution• Look at motion in orthog planes

Motion analysis: how much does the pancreas move

• Superior to inferior range– ~ 1 cm

• Medial to lateral– ~ 1 cm

• Ant – Post– ~ 1 cm

At simulation

• Full length custom cradle immobilization• Arms up overhead• Simulate on empty stomach• Oral gastrograffin at least 30 mins prior to sim• IV contrast with time delay to capture venous

phase.

Evaluate the motion

• 4D CT• Evaluate the phases of maximum exhale• Usually 40-60%• If 50% is maximum exhale, this will be primary

dataset• Fuse the 40 and 60 and the free breathing for

target delineation.

Gating box: measures respiratory excursion

Motion during treatment

SBRT planning

Beam angle selection

Blocking

Jaw setting

MLC settings

Off kidneys

Prescription

• Multi-level prescription• Prescribe to lowest dose level• Prescribe to 85% isodose

– Will adjust later• Typically 5 fractions• Start with 15 MV

– Adjust lower if needed• Equally weight all beams

– Will adjust later• Compute

Preliminary dose

Dose volume histogram

Field-in-field

MLC setting

Intermediate dose

PTV 30

DVH post calculation

Segment weight optimizer

• NOT IMRT!• SWO will not “rescue” OAR objectives• Min MU set to 10.

Segment weight optimizer

Final plan

Final DVH

Examples of Dose Painted Plans

More examples

Interesting examples

Multiple prescriptions

• The only chance a patient has for cure is if surgery is possible

• A sub-class within the unresectableclassification that is deemed borderline-resectable

• By sufficiently shrinking the tumor with neo-adjuvant therapy these cases can become resectable

• Using this technique…– Of the borderline-resectable patients more

than half have been down-staged to resectable.

• These patients are given the highest chance of long term survival.

Example outside the pancreas

Multiple PTV objectives simultaneously achieved

LIVER SBRT (GATED) 3D

Beam Angles

Pre-conformed collimators

MLC Blocking

Conformed collimators

Sup/inf opened ~1cm

Sup/inf opened ~1cm

MLC opened accordingly

Prescription

Equal weighting

Dose objectives

Dose Volume Histogram

Final Beam Weights

IMRT just for fun

Temp and Ring

Optimizer

3D versus IMRT SBRT

Questions?