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Age at developmentoflesions
5
60
a rr:is is i
Figure 47. Relationship of thyroid dose to age whenlesions develop in Marshallese. @, Benign; a, malignanc.
i
o
Percent lesions of total iesions
yg
yp
Phyruid duse (rads)
T
12
\
ceived their dose largely from radioiodines, and
the groups receiving x-irradiation. These data are
not extensive enough to show possible threshold
effects. Since in animal experiments /3!1 is only
30
a
40-50
Age at developmentoflesions
Figure 46.
hypothyroidism develops, the cases of thyroid can-
cer are fewer than expected. 120,121, 128,129 The development, in the two stunted Marshallese boys, of
thyroid atrophy with hypothyroidism but without
the developmentof tumors is in line with this reasoning. Offsetting, somewhat, the greater incidence
of thyroid cancerin childrenis the finding that chil-
about Mo to \s as effective as x-irradiation in producing thyroid tumors,85.120.129.130 why do the
Marshallese data indicate near equality of effect?
It is estimated that thousands of children have received diagnostic 1311 (20 to 50 #Ci) in the pastresulting in thyroid doses up to hundreds ofrads,
yet only | case with thyroid tumors has been reported.131.132 U.S. Public Health Service workers
recently reviewed a large numberof case histories
of people who had received radioiodines for treatment of hyperthyroidism.!22 They were unable to
show any clear-cut increase in incidence of thyroid
tumors in this group compared with a group
treated by surgical thyroidectomy. Increasing
dren survive longer than older people, even with
numbers of the patients treated with 1311 devel-
the developmentof thyroid lesions have been pre-
years. The low incidence of tumors following such
treatment may be related to the high doses of
the well differentiated types. 15?
The possible effects of the stress of puberty in
viously noted.25 Thestress of frequent pregnan-
cies, which had occurred before the development
of malignantlesions in the three Rongelap women,
may have beena factor in developmentof neoplasia. Both these correlations, however, may be
fortuitous,
2. Comparison of Thyroid Neoplasias From
X-Ray Radiation and Radioiodine Irradiation
oped varying degrees of hypothyroidism in later
radiation given to the thyroid, sufficientto destroy
its regenerative capacity.
It should be noted, however, that in the past
few years a numberof thyroid malignancies have
been reported following radioiodine therapy for
hyperthyroidism.!14116 The number of cases reported is lower than expected on the basis of dosage to the thyroid. The increased tumorigenesis in
the Marshallese mayberelated to the natureof the
Thedata in Tables 33 and 34 show thatthe risk
per rad for the developmentof thyroid neoplasms
in the Marshallese was quite similar to that in
radiation, more than half the dose being due to
short-lived isotopes of iodine (particularly 151,
Figure 44 indicate a linear relationship between
demonstrated that when these shorter-lived iso-
133], and 135]), which are more energetic (see Ap-
populations exposed to x-irradiation. The data in
pendix 9C). Vasilenko and Klassovskii!33 have
nodularity in the Marshallese children, who re-
topes of iodine are combined with 131 the tumori-
690Gb 158