Radiation-related mortality from heart disease and lung cancer more than 20 years after radiotherapy for breast cancer

BACKGROUND: Radiation-related heart disease and lung cancer can occur following radiotherapy for breast cancer but the duration of any mortality risk is uncertain. METHODS: Mortality ratios, by laterality of breast cancer, were estimated using Poisson regression for 558 871 women recorded with breast cancer during 1973–2008 in the Surveillance, Epidemiology and End Results (SEER) cancer registries and followed until 01 January 2009. RESULTS: For women diagnosed with breast cancer during 1973–1982 and given radiotherapy shortly afterwards, the cardiac mortality ratios, left-sided vs right-sided, were 1.19 (1.03–1.38), 1.35 (1.05–1.73), 1.64 (1.26–2.14) and 1.90 (1.52–2.37) at <10, 10–14, 15–19 and 20+ years since diagnosis (2p for trend: <0.001). The lung cancer mortality ratios, ipsilateral vs contralateral, in these women were 1.05 (0.57–1.94), 2.04 (1.28–3.23) and 3.87 (2.19–6.82) at <10, 10–19 and 20+ years, respectively, (2p for trend: 0.002). For women irradiated during 1983–92 there was evidence of radiation-related mortality for lung cancer, but not for heart disease. For women irradiated since 1993 there is, as yet, little evidence of any radiation-related mortality. CONCLUSION: In this population, the radiation-related risks were larger in the third decade after exposure than during the first two decades.