Second solid cancers after radiotherapy: a systematic review of the epidemiological studies of the radiation dose-response relationship
Abstract
Rapid innovation in radiotherapy techniques has resulted in an urgent need for risk projection models for second cancer risks from high-dose radiation exposure, since direct observation of the late-effects of newer treatments will require patient follow-up for a decade or more. However, the patterns of cancer risk after fractionated high-dose radiation are much less well understood than those after lower-dose exposures (0.1–5 gray (Gy)). In particular, there is uncertainty about the shape of the dose-response curve at high doses, and the magnitude of the second cancer risk per unit dose. We reviewed the available evidence from epidemiologic studies of second solid cancers in organs that received high-dose exposure (>5Gy) from radiotherapy where dose-response curves were estimated from individual organ-specific doses. We included 28 eligible studies with 3,434 second cancer patients across 11 second solid cancers. Overall, there was little evidence that the dose-response curve was non-linear in the direction of a down-turn in risk, even at organ doses of ≥60Gy. Thyroid cancer was the only exception with evidence of a downturn after 20Gy. Generally the excess relative risk per Gy, taking account of age and sex, was 5–10 times lower than the risk from acute exposures of <2Gy among the Japanese atomic bomb survivors. However, the magnitude of the reduction in risk varied according to second cancer. The results from our review provide insights into radiation carcinogenesis from…
How strong is the evidence?
Evidence Hub reads this as a systematic review, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 3,434 participants or records.
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