Comparison of supine or prone crawl photon or proton breast and regional lymph node radiation therapy including the internal mammary chain

Bruno A Speleers,Wilfried C De Neve,Annick E Van Greveling,Werner R De Gersem,Bert G Boute,Christel M Monten,Tom H Vercauteren,Liv Veldeman,Leen M Paelinck,Francesca M Belosi,Antony J Lomax,Alessandra Bolsi,Damien C Weber,Joris J Van De Velde,Pieter R Deseyne

doi:10.1038/s41598-019-41283-1

Abstract

We report on a dosimetrical study comparing supine (S) and prone-crawl (P) position for radiotherapy of whole breast (WB) and loco-regional lymph node regions, including the internal mammary chain (LN_IM). Six left sided breast cancer patients were CT-simulated in S and P positions and four patients only in P position. Treatment plans were made using non-coplanar volumetric modulated arc photon therapy (VMAT) or pencil beam scanning intensity modulated proton therapy (IMPT). Dose prescription was 15*2.67 Gy(GyRBE). The average mean heart doses for S or P VMAT were 5.6 or 4.3 Gy, respectively (p = 0.16) and 1.02 or 1.08 GyRBE, respectively for IMPT (p = 0.8; p < 0.001 for IMPT versus VMAT). The average mean lung doses for S or P VMAT were 5.91 or 2.90 Gy, respectively (p = 0.002) and 1.56 or 1.09 GyRBE, respectively for IMPT (p = 0.016). In high-risk patients, average (range) thirty-year mortality rates from radiotherapy-related cardiac injury and lung cancer were estimated at 6.8(5.4–9.4)% or 3.8(2.8–5.1)% for S or P VMAT (p < 0.001), respectively, and 1.6(1.1–2.0)% or 1.2(0.8–1.6)% for S or P IMPT (p = 0.25), respectively. Radiation-related mortality risk could outweigh the ~8% disease-specific survival benefit of WB + LN_IM radiotherapy for S VMAT but not P VMAT. IMPT carries the lowest radiation-related mortality risks.

Highlights

Radiotherapy after breast-conserving surgery improves loco-regional control and survival at the expense of acute and late local toxicity, radiation induced cardiac injury, lung cancer and cancer in the non-treated breast, leading to dose-dependent excess mortality[1,2,3,4,5,6]
Similar dosimetric differences between VMAT and Intensity Modulated Proton Therapy (IMPT) are observed in supine position
This study focused on breast and lymph node irradiation including the IM-nodes because these patients receive the highest OAR-doses[11] and because recent publications may lead to more IM irradiation[14,29]

Summary

Introduction

Radiotherapy after breast-conserving surgery improves loco-regional control and survival at the expense of acute and late local toxicity, radiation induced cardiac injury, lung cancer and cancer in the non-treated breast, leading to dose-dependent excess mortality[1,2,3,4,5,6]. The elevated arm at the treated side and device components that support the arm restrict the range of beam directions for whole breast and lymph node irradiation (WBI + LNI). We showed that prone crawl WBI + LNI (without inclusion of the IM-chain in the lymph node target) reduced heart and lung doses as compared to supine techniques[16]. Patients were positioned on the simulator couch using a Posirest arm support (Civco Medical Solutions, Kalone, Iowa, United States) with both arms elevated above the head[16]. For both positions, 5 mm slice thickness CT-images were acquired, starting at the vertex and caudally ending below the diaphragm. Photon plan optimization structures were created to reduce influence of dose buildup underneath the skin on plan optimization and to secure flash

Objectives

Results

Conclusion