Institute of Development, Aging and Cancer, Tohoku University


Seminars and Symposia

IDAC Seminar, 21 August 2014

Secretariat, Alumni Association, IDAC
Date Thursday,21 August 2014, 15:30~16:15, 16:25~17:10
Room Seminar-shitsu 1, IDAC Research building 7F
Title 1)Summary of epidemiologic studies of atomic-bomb survivors
2)How radiation exposure increases the risk of cancer; cancer induction or accelerated onset?
Speaker Nori Nakamura
Affiliation Radiation Effects Research Foundation
Person-in-charge Manabu Fukumoto Department of Pathology
Contact: Masatoshi Suzuki (ex:8509)
Person-in-charge 1) Epidemiologic studies of atomic-bomb survivors mainly consist of mortality study (120,000 subjects) and clinical study (20,000). Within 5 years after the exposure, increased risk of leukemia (especially among children) was observed while it took more than 30 years to find a clear increase of solid cancer risk. Cancer risk is expressed by relative risk and absolute risk, the former is the ratio and the latter is the difference between the mortalities of the exposed and control groups. However, the risks also vary by age at exposure and gender. As a brief summary, it can be said that 1Gy exposure causes 1.5 times increase of the relative risk of cancer. Childhood exposure is at higher risk while much of it is related to the risk of young-age onset, which does not occur otherwise. No genetic effect of radiation is detected thus far examined.
2) It has been generally thought that radiation exposure induces cancer. However, there have been no biologic models to explain epidemiologic data of the survivors. As the risks (relative and absolute risks) vary not only by age at the time of exposure but also by gender, it is a difficult task to propose a general model. As mouse data clearly indicates that radiation exposure causes earlier occurrence of cancer deaths, I used mouse data to estimate cancer risks as in epidemiologic studies and found that the apparently complex risk patterns may now be resolved.