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Left-sided breast radiotherapy after conservative surgery: comparison of techniques between volumetric modulated arc therapy, forward-planning intensity-modulated radiotherapy and conventional technique

Abstract Objective This study was conducted for comparison of techniques between volumetric modulated arc therapy (VMAT), forward-planning intensity-modulated radiotherapy (FIMRT) and conventional technique for left-sided breast radiotherapy after conservative surgery. Methods In all, 20 postoperative left breast carcinoma patients were included in this study. In all plans the planning target volume (PTV) was the breast tissue with appropriate margin as per our institutional protocol. The contouring was done on a Monaco Sim (V5.00.02) contouring workstation. All patient were planned using partial arc VMAT in Monaco treatment planning system (TPS) (V5.00.02) and treated on Elekta Synergy linear accelerator. The 3D conformal radiotherapy (3DCRT) and FIMRT planning were done in CMS XIO (V5.00.01.1) TPS. The 3DCRT planning consisted of conventional medial and tangential wedge portals with multileaf collimator field shaping conforming to the target volume. For all the plans generated the following metrics were scored: V105%, V100%, V95%, mean dose (for PTV), V5%, V20%, D2cc and mean dose (for organs at risk). Results The mean PTV volume for 20 patients was 1,074·6±405·1 cc. The highest PTV dose coverage was observed in the 3DCRT technique with 94·1±1·8% of the breast PTV receiving 95% of the prescription dose (V95%). However, it was also observed that this technique resulted in 21·3±10% of the PTV receiving more than 105% of the prescription dose (V105%), which was highest among the three techniques. In contrast, VMAT yielded lowest V95% of 93·0±1·8 and 3·3±5·5% of V105%. Conclusion This study concluded equivalent result between FIMRT and VMAT. However, VMAT was found to be the choice of radiotherapy technique as it produces lesser dose distribution to heart compared with any other technique.