| Purpose:To make a dose response analysis and risk model analysis for Chinese medical x-ray workers (CMXW) and explore lifetime and future cancer risk projections for CMXW.Materials and methods:Based on incidence data occurring in the period 1950-1995 from pooled cohort of CMXW and a comparison cohort, in terms of Poisson regression using the AMFIT model of the software package EPICURE, we made a dose response analysis and risk model analysis.For the organ dose needed for the risk analysis, firstly, based on average annual skin dose we fitted annual skin dose, and then we applied organ factors derived from ICRP Publication 74, we obtained organ and calendar year specific dose, from which we could obtained personal cumulative organ dose.Based on estimate of parameters of risk models, we obtained sex-, organ- and age-specific baseline cancer incidence rates for CMXW. And based on Chinese 2000 census mortality data, we obtained sex- and age- specific life tables. Then we applied cancer rates, life tables, and exposure histories of CMXW together with the NCI RadRisk cancer risk projection models to project radiation-related cancer cases for lifetime and 1996 or later for leukemia and cancers of the liver, stomach, thyroid, and female breast.Results:In terms of excess relative risk model, we could see that there is statistically significant dose response relationship for total solid cancer, solid cancers except cancers of thyroid and nonmelanoma skin, and liver cancer. There is no statistically significant dose response relationship for lung cancer, stomach cancer, cancers of lip oral cavity and pharynx, rectum cancer, brain cancer, pancreas cancer, colon cancer, bone cancer, female breast cancer, leukemia, esophagus cancer, bladder cancer, thyroid cancer, and nonmelanoma skin cancer.In terms of excess absolute risk model, we could see that there is statistically significant dose response relationship for total solid cancer, solid cancers except cancers of thyroid and nonmelanoma skin, lung cancer, liver cancer, stomach cancer, cancers of lip oral cavity and pharynx, rectum cancer, brain cancer, bone cancer, and nonmelanoma skin cancer. There is no statistically significant dose response relationship for female breast cancer, leukemia, esophagus cancer, and thyroid cancer.In lifetime cancer risk projection, our main results are that among estimates for all selected cancer sites, cancer of female breast is the most common form of cancer for lifetime excess cancer and future excess cancer, followed by stomach cancer. In terms of estimates of lifetime and future excess cancer risk, we could see that there would be more than half of radiation related cancers to occur in 1996 or later for all selected cancer sites among CMXW.Conclusions:Based on pooled incidence data from CMXW and the comparison cohort occurring in the period 1950-1995, we obtained excess relative risk model and excess absolute risk model and corresponding risk coefficients. Based on latest BEIR VII radiation related cancer risk models incorporated in RadRisk software; we predicted lifetime radiation related cancer risk and radiation related cancer risk since January 1st 1996 for leukemia and cancers of the liver, stomach, thyroid, and female breast. |
