Second Cancers after Radiotherapy

摘要

Conclusive evidence that radiation causes cancer comes from the studies of Japanese atomic bomb survivors, early radiation workers, and patient populations. There are well over 100 studies of patient populations linking radiation to cancer. Radiation is a relatively weak human carcinogen, in part because it is such an effective cell killer. For example, nearly 100,000 women treated with radiation for cervical cancer were required to detect a significant doubling of the risk of leukaemia , yet fewer than 1,000 women with ovarian cancer were sufficient to identify a nearly 100-fold increase in leukaemia risk due to chemotherapy. Routinely collected cancer registry data have extended our knowledge about the patterns of second cancers, especially among long-term survivors. Compared with the general population, 253,536 cancer patients in Connecticut (1935-1982) had a 31% (RR = 1.31) increased risk of developing a second cancer. Among 1,423,161 cancer patients in NCI SEER registry regions (1972-1993), second cancers developed in 95,000 persons compared with 87,000 expected (RR = 1.09). Over 50% of these new cancers were of the lung, breast, colon and prostate.