Radiation and breast carcinogenesis

With the possible exception of radiation-induced leukemia, more is known ab out radiation-induced breast cancer than any of her malignancy [1,2]. Fourt een cohort studies have provided quantitative information on the level of r isk following a wide range of doses in different populations around the wor ld. Comprehensive studies have been conducted in Canada, Germany, Japan, Sw eden and other Nordic countries, the United Kingdom, and the USA (Table I). Key features are the linearity in the dose response (i.e., a straight line adequately fits the observed data), and the effect modification of age at exposure (i.e., risk is inversely related to exposure age and exposures pas t the menopausal ages appear to carry a very low risk); and the minimal eff ect of fractionating dose on subsequent risk [3]. A recent combined analysi s of almost 78,000 women and 1,500 breast cancer cases from eight cohorts c onfirmed the downturn in risk at the highest dose levels (related in part t o the killing of cells rather than transformation) and that fractionation o f dose has little influence on risk, at least on an absolute scale [4]. It is not known whether persons predisposed to cancer are at enhanced risk of radiation-induced breast cancer from low-dose exposures, although this seem s unlikely [5]. New data on the effects of high doses following childhood e xposures will be forthcoming from long-term studies of the survivors of chi ldhood cancer (6-8). Med. Pediatr. Oncol. 36:508-513, 2001. (C) 2001 Wiley- Liss, Inc.