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Page 5 - Geneva Douglas
Some valuable information has come out of the ABCC evaluations of those
people exposed at the time of the A Bomb. This is true even though dose
estimates and patient follow-up have been difficult. Autopsy studies
of 1,215 exposed patients (14% of whom were exposed within 1,400 m of
the hypocenter, and hence probably received greater than 100 rads)
showed 2] thyroid malignancies. The number expected on the hypothesis
of no relationship between thyroid cancer and distance is 3. The
probability of observing so large an excess by chance is 0.023 (one
tail).
In only 3 of the 21 was carcinoma considered to nave contributed
to the death of the patient.
The remaining 18 lesions were minute,
seldom measuring more than 1.5 cm across, and were usually first
recognized on histological exam. They were non-aggressive lesions
("non-encapsulated sclerosing’) with an excellent prognosis.
During 1958-61 some 10,780 exposed Hiroshima patients involved in Adult
Health Study program were examined, and 310 enlarged thyroids were found.
102 were single nodules, 70 were biopsied, and in the group exposed at
distances less than 2,000 m, and who showed acute symptoms at the time
of the bomb, 10 had thyroid malignancy.
Conclusions which have been drawn by the ICRP regarding radiation induced
thyroid cancer include:
1.
2.
A careful distinction between frequency of induction and frequency
of death must be made in any discussion of radiation induced thyroid
cancer.
Due to the limitations of dose estimates and epidemiological techniques,
underassessment of the number of cases and overassessment of dose,
each lead to an underestimate of the yield of thyroid cancer per rad.
It was concluded that as a working rule the total risk in exposed
Japanese was about 20-30 cases per rad per million exvxosed with little,
if any, variation with age at time of exposure.
Z. & Af
Lawrence E. Holder, M.D.
Medical Advisor
cc:
——=M. W. Carter
J. E. Regnier
J.
R. McBride