66
tients after radiation treatment for ankylosing
spondylitis, !49 etc.), and its etiological role was
near death. In spite of the long-term findings,
morbid evidence of the disease was not apparent
bomb,130.151
nosis of leukemia the peripheral blood cells appeared normal except for a possible increase in
established without question by the high incidence
of leukemia in the Japanese exposed to the atom
Somefindings in the Japanese tend to support
radiation etiology in this Marshallese boy. In his
case the latent period was quite long, but thein-
cidence of leukemia in Japan is still (after >25
years) higher among the exposed group than
among the general population. Also, the incidence
has been higher among those exposed in child-
hood, particularly males, in whom the granulocytic
form of leukemia has been prevalent; and the same
form has been more prevalent in cases with longer
latent periods and lower exposures.15? On the
basis of 2 cases per year per million people per
rad amongthe exposed Japanese, the expectancy
among the exposed Marshallese would bea total
of about0.33 cases. However, the normal incidence
of leukemia in the Marshallese, from the sketchy
statistics available, appears to be low, about 20
cases per year per million compared with 60 to 70
in the U.S.; thus the number of spontaneous cases
expected amongthe exposed Marshallese would
be a total of 0.02 to 0.067. The ratio of radiationinduced to spontaneous expectancy(0.33:0.02 or
0.33:0.067) indicates that chances are about5 to
15 times as great that this Marshallese case was
radiation-induced as that it was spontaneous.
Review of the hematological data on subject
No. 54 over the 18-year period before the developmentof leukemia is of interest. The greater degree
of hematologic depression in him thanin the other
exposed boys indicates either a greater radiation
dose to the hematopoietictissues or greater sensitivity or proclivity to marrow depression. (None
of the peripheral granulocyte levels in the other
boys, exposed or unexposed, plotted individually,
were as low as his.) Perhaps his radiation dose was
actually greater, since he was the youngest Ron-
gelap child exposed and maytherefore have been
in closer contact with the fallout source on the
ground. Being younger mightalso imply greater
radiosensitivity.
In view ofthe later developmentof the granulocytic form of leukemia, it is of interest that the
until the last few months. One vearbefore the diagatypical monocytes.
A preleukemic syndrome has been described for
some cases of nonlymphocytic leukemias.!53.154
Linman and Saarni!54 state that the frequency of
the syndrome maybeas high as two cases in five
and that preleukemic findings “reflect the early
stage of myeloproliferative disorders which will
eventually fulfill the criteria to be classified as myelomonocytic leukemias.”’ The syndromeis characterized by various findings, not all necessarily
present, such as anemia with erythrocyte abnormalities, thrombocytopenia, atypical platelets in the peripheral blood, and neutropenia. 153.154 Chromosome abnormalities are reported in abouthalf the
cases. /53 Isolated neutropenia is an occasional pre-
leukemic finding; in the case reported here, the
relative neutropenia is the only finding that might
be considered as preleukemic. If the preleukemic
phaseis considered to date back to near the time
of radiation exposure in this case, then it had a
longer course than is usually noted.154
The possibility that the granulocytic reserve was
reduced in subject No. 54 as a result of radiation
exposure was indicated by his granulocyte response
being lower than thatof his peers in response to
challenge by childhood infections. One might speculate that the frequent infections to which the
Marshallese are exposed may have played a role
in accelerating the development of a radiationinduced mutantleukemic clone. This would be
similar in some ways to the role thought to be
played by the thyroid-stimulating hormonein enhancing the development of tumorsin radiation-
injured thyroid glands, as has been seen in the
Marshallese years after exposure of their thyroid
glands to radioiodine from thefallout. The above
findings do not rule out the possibility of a viral
etiology for this leukemia.
Because of the developmentofthis case of leu-
kemia, complete hematological examinations on
the exposed Marshallese population are now being
carried out semiannuaily instead of annually.
early bone marrow injury was characterized by
having the greatest effect on the granulocytes, with
the thrombocytic and lymphocytic cells less af-
fected and the erythrocytic cells least. The erythrocytic system did not show evidence offailure until
JO0b1b3
B. OTHER MALIGNANCIES
Malignancies other than thyroid cancer and
leukemia (see Table 35) appeared to have a higher