Rapidarc vs. tomotherapy for the treatment of chestwall and lymph nodes: A comparative study

Abstract

Introduction Treatment of chestwall with lymph nodes (internal mammary and clavicular nodes) is achieved in most of the centers with conventional radiotherapy using photons and electrons beams with junctions. The aim of this study is to do a dosimetric comparative study between two technics using modulation irradiation: Tomotherapy and Rapid Arc (RA). Material and methods Seven patients (5 left, 2 right) were treated using Tomotherapy. For these patients a RA plan was prepared retrospectively. Patients were positioned supine with two arms above the head. The prescribed dose was 50 Gy for the chestwall and 46–50 Gy for the lymph nodes. Optimisation constraints were increased until the PTV coverage was acceptable. Tomotherapy plans were computed with a 2.5–5 cm collimation and a 0.287 pitch. RA plans were computed using a 5 mmbolus on the chestwall, 2 arcs (60–180°) and a +/-10° collimator rotation. Doses delivered to targets, heart and both lungs are reported. Results For the 7 patients the heart mean dose was 7.1–8.6 Gy (mean 7.5 Gy) with Tomotherapy and 4.4–18.1 Gy (mean 9.9 Gy) for RA. For the ipsilateral lung, the mean dose, V5, V20 and V30 were respectively 10.1–14.7 Gy, 56.4–85.7%, 14.8–25.9% and 6.2–16.6% for Tomotherapy. For RA, these values were 10.5–16.0 Gy, 65.3–96.0%, 14.8–30.0% and 6.2–16.6%. Conclusion For 5/7 patients RA plans were acceptable but the OAR doses were generally higher than Tomotherapy plans (in particular V5 of lungs and lung mean dose). For 2/7 patients (left side) RA plans were not acceptable.