Date post: | 08-Jul-2018 |
Category: |
Documents |
View: | 227 times |
Download: | 0 times |
of 10
8/19/2019 Mettler THyroid cancer
1/21
Medical Effects of Ionizing Radiation
Chapter 5. Carcinogenesis of Specific SitesThyroid Cancer~
8/19/2019 Mettler THyroid cancer
2/21
Thyroid Cancer
• General – About 1~2% of all cancers – igh rates in
• a!aiian Islanders• "illi#ino i$$igrants of a!aii and California• ati&e Alas'an !o$en• (o#ulation of Iceland
– T!ice as co$$on in fe$ales as in $ales – Increasing incidence rates !ith age – )*+ ordic contries
• Increasing incidence rates for both se,es+ es#ecially in the younger grou#s-
– Euro#e• Incidence rising+ but $ortality is declining-
./ Increased diagnosis $ay be the reason of the increasing-
8/19/2019 Mettler THyroid cancer
3/21
Thyroid Cancer
• General 0cont- – .year sur&i&al is a ##ro,i$ately 3 % for all ty#es of thyroid tu$ors-
• The $a4ority is !ell.differentiated carcino$as-• Robbins et al- 5 6% due to radiation-
– "atality rate of radiation.induced thyroid tu$ors is 7~6%• 8.ray+ ga$$a radiation+ internally de#osited radionuclides $ay induce thyroid carcino$a-• Ris' esti$ation based on the linear.no.threshold $odel+ but not a##licable at &ery high absorbed
doses 0because of cell 'illing -
– The $a4ority of thyroid cancers induced by radiation are !ell.differentiated #a#illary adenocarcino$as-
• A lesser #ercentage of follicular-• "or the $ost #art+ being associated !ith long sur&i&al #eriods-
– 9ccult carcino$a 5 on radiogenic and clinically nonsignificance – *e&eral cases re#orted as follo!ing radiation e,#osure- :ut uncertain if indeed radiation.
induced- – The geno$ic signature and aggressi&e nature of the tu$or $ay re#resent the ty#e of th
yroid cancer that occurs in childhood-
8/19/2019 Mettler THyroid cancer
4/21
Thyroid Cancer
• Modifying "actors1. The ty#e and duration of e,#osure
• ;ose rate effect 5 Acute e,ternal radiation is $ore effecti&e in causing radiogenic thyroidtu$ors than iodine 171-
•
8/19/2019 Mettler THyroid cancer
5/21
Thyroid Cancer
External Exposure – igh natural bac'ground
• igh.bac'ground area $ortality due to thyroid cancer./ nonsignificantly ele&ated
e, Tao et al- *tudy in ?ang4iang+ China• Airline cre!s ./ 7 cases a$ong o&er 1@+@@@ ordic #ilots onsignificant increase
– Ato$ic :o$b *ur&i&ors• iroshi$a+ agasa'i 5Thyroid cancer induction has been a##arent-
– Rates a##rear be ~2@ cases in 1 $illion #ersons for each 1@$Gy- – The increase in ris' !as statistically significant at a dose of about @-7 Gy
• igher induction rate in fe$ales by a factor / 2• o significant difference in the ERR bet!een $ales and fe$ales-• Ris' decreased !ith age at e,#osure-
8/19/2019 Mettler THyroid cancer
6/21
Thyroid Cancer
External Exposure (cont.) – (o#ulations ear uclear "acilities
• *tudies sho!ing nonsignificant increased ris' in thyroid cancer- – 9ccu#ational E,#osure
• Generally nonsignificant increase – Mostly based on $ortality statistics- – The !or'ers are all adults and doses are relati&ely lo!-
• A study by *on et al- 5 The first analysis of cancer incidence – The *IR for thyroid cancer !as nonsgnificantly ele&ated 01-72 - – The *IR for fe$ales !as significantly ele&ated 01-=2 -
– Medical diagnostic e,#osure• o increased ris' of thyroid cancer !a found-
8/19/2019 Mettler THyroid cancer
7/21
Thyroid Cancer
External Exposure (cont.) – Radiation thera#y
• e$#el$ann el al- – 23 2 8.ray thera#y for #resu$ed thy$ic enlarge$ent – Gi&en in infancy – Mean thyroid dose 1-16 Gy – Absolute ris' !as 1- cases B 1 $illion for each 1@ $Gy !ith >e!ish e,cluded- – *hore et al- re#ort at a $ean follo!.u# ti$e of 7 years 5 7 thyroid cancers in the e,#osed grou# B in sibling controls 077 !ere #a#illary+ = !ere follicular Earliest years after e,#osure B
8/19/2019 Mettler THyroid cancer
8/21
Thyroid Cancer
• E,ternal E,#osure 0cont-• Ron and Modan
– Israeli #atients treated !ith ,.ray – Thyroid dose 6@ $Gy – Dithout >e!ish+ ris' factor 17 cases B 1 $ilion for each 1@ $Gy
• Thyroid nodules+ benign and $alignant+ re#orted after high.dose e,ternal RT – Chicago Michael Reese os#ital study
• E,ternal RT to the head+ nec'+ or chest before or during adolescence+#redo$inantly for tonsillar hy#ertro#hy ./ 7~= ti$es ris' esti$ation
– Thyroid nodules 0benign and $alignant re#orted after high.dose e,ternal RT-
8/19/2019 Mettler THyroid cancer
9/21
Thyroid Cancer
Internal Exposure – 9ccu#ational E,#osure
• Internal occu#ation e,#osure and subse uent ris' of thyroid cancer are fe!0*e&eral re#orts -
– Medical E,#osure• ;iagnositic #ur#ose 0Radioacti&e iodine.171
– The cancer incidence didnFt increase or increased statistically nonsignificant increase- – More cases in the fe$ale #o#ulation
• Treat$ent of hy#erthyroidis$ – Generally+ #atients !ho ha&e recei&ed &ery large ad$inistrated acti&ities of iodine 171 ha&e
not de$onstrate radiogenic thyroid neo#las$s- – ;oses high enough to treat hy#erthyroidis$+ cell 'illing is the #redo$inant effect-
8/19/2019 Mettler THyroid cancer
10/21
Thyroid Cancer
Fallout – uclear !ea#on fallout
• *e&eral studies about the effect of an internal e,#osure fro$ fallout ./ o significant difference bet!een irradiated and nonirradiated sub4ects-• :oth e,ternal and internal irradiation 5 Marshall Islands
./ Esti$ated ris' !as 1= cases B 1 $illion for each 1@ $Gy ./ All the cancer occurred in fe$ales- 0 igher induction rate in fe$ale ./ Ma4or contributions to dose 5 shor.li&ed iodines 0I.172+ 177+ 17 5 The effect of shorter.li&ed isoto#es are $ore li'e e,ternal
radiation e,#osure than fro$ I.171- 0Conrad• In #resent ti$e+ assu$e that ris' factor of
./ *hort.li&ed radioiodines 0Iodine 172+ 177+ 17 is close to that of e,ternalirradiation
./ The longer.li&ed iodine 12 is close to that of iodine 171 – anford 5 ;a&is et al- + o significant increase in thyrid cancer induced by
the effect of radioiodine fro$ the anford nuclear facility-
8/19/2019 Mettler THyroid cancer
11/21
Thyroid Cancer
Fallout (cont.) – Chernobyl
• "our co$#onents of the thyroid doses1. Internal irradiation fro$ inta'es of I.1712. Internal irradiation fro$ inta'es of short.li&ed radioiodines and shor
t.li&ed radiotelluriu$s3. E,ternal dose fro$ radionuclides de#osited on the ground 0Cs.17 +
Cs.17=4. Internal inta'es of long.li&ed radionuclides
• I.171 ta'es 3@ % of the total thyroid dose+ and #redo$inantly fro$ ingestion of co!Fs $il'-
8/19/2019 Mettler THyroid cancer
12/21
Thyroid Adeno$as and odules
• :enign thyroid – :enign thyroid neo#las$s can occur after irradiation- – :enign adeno$as do not see$ to ha&e a $alignant #otential-
• Co$#licated by a nu$ber of issues in e#ide$iologic studies1. Dith the de&elo#$ent of high.resolution ultrasound i$aging+ $any $ore no
dules can be &isualized-2. ;efinition of the ter$ noduleH is not al!ays the sa$e-
• The #re&alence of thyroid nodules in none,#osed #o#ultions &ary !idely- 0 to @ %
3. The #resence of goiterH• )nclear !hether the goiter is an enlared gland or a nor$al.sized gland !ith a nodule-
8/19/2019 Mettler THyroid cancer
13/21
Thyroid Adeno$as and odules
External Exposure• atural :ac'ground Radiation
– Dang et al- high.bac'ground areas of China study about thyroid nodularity ./ onsignificant difference
• Ato$ic :o$b *ur&i&ors – Thyroid nodules and adeno$as increase re#orted in sur&i&ors in agasa'i- – *trangely no relation of thyroid cancer to radiation dose
• Medical E,#osure – a#lan et al- Analysis of #atients e,#osed to $ulti#le fluorosco#ies ./ The #re&alence rate of thyroid nodules !as nonsignificantly ele&ated- – odule induction after childhood radiation thera#y for benign entities- – The occurrence of thyroid adeno$as in children after radiation e,#osure for tr
eat$ent of thy$ic enlarge$ent- ./ o increased ris' in less than 17 years after e,#osure-
8/19/2019 Mettler THyroid cancer
14/21
Thyroid Adeno$as and odules
Internal Exposure• Medical e,#osure
– The #re&alance of thyroid nodularit !as unclear-• "allout
–
uclear !ea#ons• A higher than e,#ected incidence of thyroid cancer and thyroid nodules re#orted-• The ris' in fe$ales is higher than that in $ales-• The #re&alence of thyroid nodules decreased !ith distance fro$ the test site- 0 a$ilton el al-
– anford• o increased incidence of benign nodules-
8/19/2019 Mettler THyroid cancer
15/21
:reast Cancer
• 72 % of all $alignanies in !o$en• Incidence &aries !ith geogra#hical area
– ighest in a!aiian !o$an+ and )-*- !hite !o$en- – a#an-
• Increase !ith age fro$ 7@ to @ years 0#lateau at = ~ @• Modifyng "actors
– Race 5 igh incidence rate of >e!s – Genetic co$#onent of fe$ale breast cancer
• @ % ris' if a cancer occurs in a #re$eno#ausal sister and a $other-• *o$e suggest that the incidence as a result of a A.T trait-
– Marrital status 5 More co$$on in single than in $arried !o$en- – 9&arian function 5 Castration substantially reduces ris'-
8/19/2019 Mettler THyroid cancer
16/21
:reast Cancer
• Modifyng "actors 0cont- – Age at first #regnancy 5
• A !o$en !ith full.ter$ #regnancy under the age of 13 years ha&e one third the ris' of !o$en !ho delay #regnancy until age 7@-
• )ntil the !o$en reach the age that s#ontaneous breast cancer usually occur+ radiogenic tu$ors generally do not a##ear-
• Age at e,#osure 5 Most studies suggest sho! that breast cancer ris' decreases re$ar'edly !ith increasing age at e,#osure-
– Total dose• Acute doses J 7 Gy linearly realated to ris'-• At higher doses+ the ris' sho! a #lateau and decreases at doses / Gy
– Effect of fractionation do not a##ear to be large e,ce#t in the radioiodine stu
dies-
8/19/2019 Mettler THyroid cancer
17/21
:reast Cancer
• Ris' factors for breast cancer follo!ing radiation e,#osure1. Ato$ic bo$b sur&i&ors ./ instantaneous e,#osure2. (atients !ho ha&e had e,#osure to diagnostic radiation
./ e,#osure o&er se&eral years3. Indi&iduals !ho ha&e had radiothera#y to the breast
./ e,#osure o&er se&eral !ee'sK/ The ris' esti$ates of three grou#s are si$ilar-
•. :reast cancer $ay be induced !ith a reasonably high fre uency after radiation e,#osure at age under =@-
•. @% of radiation.induced breast cancers are fatal-•. The statistical fit to the a&ailable dose.res#onse relationshi# is a##ro,i$
ately linear-
8/19/2019 Mettler THyroid cancer
18/21
8/19/2019 Mettler THyroid cancer
19/21
8/19/2019 Mettler THyroid cancer
20/21
8/19/2019 Mettler THyroid cancer
21/21