A case of multiple primary cancers (MPC) is defined as two or
more independent primary cancers arising in different organs in
the same individual (ex: gastric cancer and colon cancer, thyroid
cancer, breast cancer, and skin cancer, etc). The occurrence of
MPC is considered to be a reflection of systematic exposure to
environmental carcinogens or of a predisposition to cancer. A
higher incidence rate of MPC was revealed in A-bomb survivors,
particularly for those who were exposed at a younger age and
closer distance from the hypocenter (A). The incidence rate of
MPC continued to increase annually, and significantly higher in
the proximal group than the distal group (distance from hypocenter)
since 1980 s (B). These results provide evidence for the
involvement of A-bomb radiation in MPC among the survivors.
A higher risk of MPC, as a late effect of A-bomb radiation, will
still persist in survivors.
[Nakashima M. et al., Cancer Sci. 99, 87-92, 2008]
A: Incidence rate of multiple primary cancers in Nagasaki A-bomb survivors
by exposure distance (1968-1999)
B: Time trend of incidence rate of multiple primary cancers in Nagasaki A-bomb survivors in each distance group
