Multi-institutional international investigation of VMAT treatment planning techniques for breast cancer with regional lymph nodes

Abstract

Background Despite constant developments in radiotherapy, optimizing Volumetric Modulated Arc Therapy (VMAT) dose distributions for whole breast with extensive lymph node involvement remains a challenge. The aim of this study was to gain insights into clinical practices and to identify effective planning strategies. Methods The participants of the European Federation of Organisations for Medical Physics VMAT Breast Working Group answered a survey regarding treatment planning routines for breast cancer irradiation and generated a treatment plan for a challenging patient case. The dose prescription was 50.4 Gy in 28 fractions for breast and lymph node volumes, and a simultaneous integrated boost (SIB) of 63 Gy. Results The survey was completed by 25 participants and covered a wide spectrum of topics of VMAT treatment planning, including beam geometry and organs at risk (OAR) dose constraints. In addition, 22 plans were submitted for comparison. The mean doses ranged between: PTV breast 51.9–––54.1 Gy, PTV lymph nodes 49.7–––52.1 Gy, SIB 61.5–––66.5 Gy, heart 1.5–––9.5 Gy, ipsilateral lung 12.0–––17.3 Gy, contralateral lung 1.2–––6.5 Gy and contralateral breast 1.6–––8.9 Gy. Five treatment planning strategies, with high target coverage and the lowest doses to organs at risk, are presented. Conclusion There is a wide variation in VMAT breast planning approaches, planning goals and prioritisation of PTVs and OARs across institutions. Descriptions of effective planning strategies for a challenging breast case are presented.