Heart exposure in 100 consecutive, unselected patients treated with adjuvant 3D conformal radiotherapy for left-sided breast cancer.

Abstract

103 Background: Women treated with radiotherapy for left-sided breast cancer may have their heart exposed to doses ranging from 1 to 7 Gy on the average. This was confirmed by a recent study* focusing on the ischemic risk based on medical records dating back to 1950s. Modern 3D conformal radiotherapy (3D-CRT), however, may play a major role in heart-sparing irradiation. Methods: We reviewed the treatment planning records and dose-volume histograms of 100 consecutive, unselected patients (pts) affected with left-sided breast cancer who underwent adjuvant 3D-CRT after either quadrantectomy (90 pts) or mastectomy (10 pts) in our center during the year 2011. Median age was 52 (range 42-90). The whole breast (or chest wall) received 50 Gy / 25 fractions in 66 pts and 45 Gy / 18 fractions in 34. Boost to surgical bed (10 Gy / 4-5 fractions) was delivered by photons in 10 pts. Median number of tangential fields was 2 (range 2-4). All treatments were performed in the supine position. Results: The average of the median doses to the whole heart was 2.89 Gy (range 0.8 to 13.05). Median doses were: 1.15 to 1.99 Gy in 21 pts; 2.01 to 3.00 Gy in 32 pts; 3.06 to 3.98 Gy in 16 pts; 4.16 to 4.83 Gy in 13 pts. Median dose only exceeded 5 Gy in 17 pts. One pt received less than 1 Gy and one pt more than 13 Gy. Median volumes (mV) of heart exposed to 5 Gy, 10 Gy and 15 Gy were: mV5 ≤ 4% (range 1 to 42%), mV10 ≤ 3% (0 to 30%), mV15 ≤ 2% (0 to 24%). Conclusions: The average doses we registered are lower than those (4.9 Gy, range 0.03 to 27.72) reported in the large investigation by Darby et al.*. Although related to a small case series, our data confirm that contemporary 3D conformal techniques allow reduced median doses to the whole heart with potential favorable impact on the risk of radiation-induced cardiac disease in the coming decades. Estimate of cardiac involvement in breast cancer radiotherapy based on older case series and outdated treatment techniques may be misleading. *Darby SC et al. Risk of ischemic heart disease in women after radiotherapy for breast cancer. NEJM 368, 11, 2013.