A Systematic Review of Heart Dose in Breast Radiotherapy

Radiotherapy (RT) for breast cancer improves survival, but poses risk to the heart, resulting from a linear relationship between RT dose and heart disease. This review presents studies worldwide reporting heart doses from whole breast RT after 2014 to update a previous systematic review (Taylor et al, Int J Radiat Oncol Biol Phys, 2015) in order to determine patterns of current heart dosimetry among varying RT regimens. Studies published between January 2014 and September 2017 were included if they reported whole heart dose based on whole breast RT technique or treatment position and had a sample size of ≥ 20 patients. Studies reporting brachytherapy, proton RT only, or boost to tumor bed were excluded. Among 99 studies, whole heart dose was reported by 231 regimens. The mean heart dose for left-sided breast cancer, reported by 84 studies (196 regimens), was 3.6 Gy, compared with a review of those previously reported (5.4 Gy). Regimens employing breathing control in any position had a significantly lower mean heart dose (1.7 Gy) compared with regimens without breathing control (4.5 Gy) (P < .0001). The mean heart dose varied significantly between continents (P < .0001), with heterogeneity reported among countries within Europe (P = .04) although not within other continents. On average, the mean heart dose steadily decreased between 2014 (4.6 Gy) and 2017 (2.6 Gy) (P = .003). Other heart dose parameters including the mean dose to the left anterior descending artery were reported by 80 left-sided regimens, and the mean left anterior descending artery dose was 12.4 Gy.