A two-phase Poisson process model and its application to analysis of cancer mortality among A-bomb survivors.
We consider a two-phase Poisson process model where only early successive transitions are assumed to be sensitive to exposure. In the case where intensity transitions are low, we derive analytically an approximate formula for the distribution of time to event for the excess hazard ratio (EHR) due to a single point exposure. The formula for EHR is a polynomial in exposure dose. Since the formula for EHR contains no unknown parameters except for the number of total stages, number of exposure-sensitive stages, and a coefficient of exposure effect, it is applicable easily under a variety of situations where there exists a possible latency time from a single point exposure to occurrence of event. Based on the multistage hypothesis of cancer, we formulate a radiation carcinogenesis model in which only some early consecutive stages of the process are sensitive to exposure, whereas later stages are not affected. An illustrative analysis using the proposed model is given for cancer mortality among A-bomb survivors.
Department of Environmetrics and Biometrics, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan. Electronic address: ohtaki@hiroshima-u.ac.jp.
Megu
M
Ohtaki
Department of Management Information Systems, Faculty of Management and Information Systems, Prefectural University of Hiroshima, 1-1-71 Ujina-Higashi, Minami-Ku, Hiroshima 734-8558, Japan.
Tetsuji
T
Tonda
Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo 153-8505, Japan.
Kazuyuki
K
Aihara
D006801:Humans; D008962:Models, Theoretical; D009369:Neoplasms; D009381:Neoplasms, Radiation-Induced; D054043:Nuclear Weapons; D016012:Poisson Distribution; D017741:Survivors
Excess hazard ratio; Latency of cancer; Multistage model; Poisson process; Radiation carcinogenesis; Single point exposure