Left‐sided breast cancer loco‐regional radiotherapy with deep inspiration breath‐hold: Does volumetric‐modulated arc radiotherapy reduce heart dose further compared with tangential intensity‐modulated radiotherapy?. Issue 4 (20th April 2016) - Pham, Trang T
Abstract: Introduction: Left‐sided breast cancer radiotherapy has been associated with an increase in cardiac mortality. This study investigated the potential heart‐sparing effect of volumetric‐modulated arc radiotherapy (VMAT). We compared VMAT to tangential intensity‐modulated radiotherapy (t‐IMRT) in the loco‐regional treatment of left‐sided breast cancer, including internal mammary nodal irradiation, based on deep inspiration breath‐hold (DIBH) and free‐breathing (FB). Methods: Radiotherapy for 15 patients was re‐planned. Four plans were compared: t‐IMRT‐DIBH; VMAT‐DIBH; t‐IMRT‐FB; VMAT‐FB. Prescribed dose was 50 Gy in 25 fractions. T‐IMRT plans were generated using tangentially orientated fields. VMAT plans were generated using two partial arcs (average arc 190°). Results: Mean heart dose (MHD) was 5 ± 2.4 Gy, 5.7 ± 1.4 Gy, 9.7 ± 3.3 Gy and 8.1 ± 2.0 Gy for t‐IMRT‐DIBH, VMAT‐DIBH, IMRT‐FB and VMAT‐FB respectively. The difference in MHD between IMRT‐DIBH and VMAT‐DIBH was not significant ( P = 0.14). VMAT‐DIBH significantly spared the volume of heart irradiated to doses of 20 Gy and above ( p < 0.05), however, resulted in a significantly higher V5 Gy ( P < 0.001), compared to t‐IMRT‐DIBH. VMAT‐DIBH resulted in higher combined lung mean (11 ± 0.8 Gy vs. 8.8 ± 1.1 Gy, P < 0.001) and higher contralateral breast mean dose (5 ± 1 Gy vs. 1.6 ± 1.2 Gy, P < 0.001) compared with t‐IMRT‐DIBH. Conclusions: On average, there was no significant difference in MHD between VMAT‐DIBH and t‐IMRT‐DIBH. However, VMAT‐DIBH was found to benefit a select group of patients. For patients in whom the MHD was >6.3 Gy with t‐IMRT‐DIBH, the use of VMAT‐DIBH resulted in a benefit in reducing the MHD.