These findings indicate that up to a point, perhaps in the range of 1500-2000 cGy, the greater the radiation dose the greater is the chance of a detected thyroid nodule being cancerous. 60 8) t t t T T (a) Adenomatous Nodules 50/7 oO J =Cc 20+ a= o 8 oe a o oe z & pe 0 A 26 . a , Of 10m , ™ | q ' & 4 _- = (4 © 22F Occult Papillary Carcinomas 146 Rongelapo Utirik = cos i F186 $ F 10+ oT 0 Fig.7 | Rongelap>2 L gE . oF a \ I 1 T T T T T Carcinomas oo r 14 + 10F 4 ! 7 18F + 4 . ] aaa 5 l 20 1 j 40 Lk 4 2 60 0 — 1 -m 1 20 j a 1 40 1 Relation of thyroid-absorbed dose to age at exposure categorized by nodule histology. Casualty Commission in Japan indicated that occult thyroid carcinomas were increased by radiation exposure (Sampson et al., 1969), although there is at least one subsequent study from Nagasaki that found no such increase (Wakabayashiet al., 1983). In the exposed Marshallese a similar effect may also be present, for based on results of surgical exploration, 6 of 24 (25%) of Utirik persons exposed to radiation (thyroid-absorbed doses ranging from 170 to 680 cGy) had occult carcinomas. However, in the Rongelap group, 22 =~ 4 J Age at exposure in 1954 (yrs) 7) Did radiation increase the incidence of "occult" carcinomas? Occult thyroid carcinomas have been found in 6-36% of routine autopsies in many parts of the world (Fukunaga and Yatani, 1975; Harachetal., 1984), and the prevalence does not increase with age, in contrast to overt carcinomas and benign lesions. In 23 unexposed Marshallese undergoing thyroid surgery under the auspices of the Brookhaven medical program, 2 (9%) had occult carcinomas. Reports from the Atomic Bomb 7 : ai l | () J Rongelapo Utirik = a 5 4 4 1 | 77f- i 4-1 41 4 4 9 or .a 26 = Utirik 10kr > a 2k a a 2 _& T ' 18F 14F a (b) 1 Adenomas - = Utirik ° 37 2oy@ T —T T T T + 4 227 Rongelap © 40 r o” 4) O> 26 7 60