Cardiac doses from Swedish breast cancer radiotherapy since the 1950s.

PURPOSE: To estimate cardiac doses from breast cancer radiotherapy in Sweden from the 1950s to the 1990s. These doses will contribute to deriving dose-response relationships for the risk of radiation-induced heart disease. MATERIALS AND METHODS: The Swedish nationwide cancer register was used to identify women irradiated for breast cancer in the Stockholm area. Virtual simulation, computed tomography planning, and manual planning were used to reconstruct radiotherapy regimens. Estimates of heart and coronary artery dose were derived for each woman. RESULTS: Cardiac doses were assessed in 358 women. Mean heart dose varied from <0.1 to 23.6 Gy and mean left anterior descending coronary artery dose varied from 0.1 to 46.3 Gy. Mean heart doses averaged across women irradiated in each decade for left-sided and right-sided breast cancers, respectively, were 5.1 and 1.8 Gy in the 1950s, 10.5 and 4.7 Gy in the 1970s and 3.0 and 1.9 Gy in the 1990s. CONCLUSIONS: Cardiac doses from Swedish breast cancer radiotherapy increased from the 1950s to the 1970s, and then reduced substantially in the 1980s and 1990s. The wide range of doses observed should provide substantial statistical power for the estimation of dose-response relationships for radiation-induced heart disease.