Comparison of conventional radiotherapy and intensity-modulated radiotherapy for post-operative radiotherapy for primary extremity soft tissue sarcoma

IntroductionDoses in conventional radiotherapy for extremity soft tissue sarcoma (STS) potentially exceed normal tissue tolerances. This study compares 3D-conformal radiotherapy (3D-CRT) with intensity-modulated radiotherapy (IMRT) in optimising target volume coverage and minimising integral dose to organs-at-risk (OAR).Methods and materialsTen patients undergoing post-operative radiotherapy for extremity STS were assessed. PTV1 was defined as tumour bed plus 5 cm superiorly/inferiorly and 3 cm circumferentially, PTV2 was defined as 2 cm isotropically. OAR were defined as whole femur, neurovascular bundle, tissue corridor and normal tissue outside PTV1. For each patient 2-phase 3D-CRT was compared to 2/3 field (2/3f) and 4/5 field (4/5f) IMRT with simultaneous integrated boost (SIB). The primary planning objective was to minimise femur and skin corridor dose. Volumetric analysis and conformity and heterogeneity indices were used for plan comparison.ResultsA planning protocol containing dose/volume constraints for target and OAR was defined. 4/5f IMRT showed greatest conformity and homogeneity. IMRT resulted in significantly lower femur V45 using 2/3f (p = 0.01) and 4/5f (p = 0.0009) than 3D-CRT. 4/5f IMRT resulted in significantly lower normal tissue V55 (p = 0.004) and maximum dose (p = 0.04) than 3D-CRT.ConclusionsA reproducible set of planning guidelines and dose–volume constraints for 3D-CRT and IMRT planning for extremity sarcomas was devised. 4/5f IMRT with SIB resulted in better target coverage and significantly decreased OAR dose. Further evaluation of this technique within a clinical trial is recommended to demonstrate that the technical benefit of the more complex technique translates into patient-derived benefit by reducing late toxicity.