mettler thyroid cancer

8/19/2019 Mettler THyroid cancer

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Medical Effects of Ionizing Radiation

Chapter 5. Carcinogenesis of Specific SitesThyroid Cancer~


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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-


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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-


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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-

•


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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-


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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-


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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


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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-


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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-


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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-


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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'-


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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-


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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-


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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-


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: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'-


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: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-


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: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-


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mettler thyroid cancer

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