Dosimetric Comparison of VMAT and HDR Brachytherapy in Sparing Organs-at-Risk in Gynecological Radiation Therapy

Background & Objective: Cancer involves the abnormal and uncontrolled growth of certain cells that can spread throughout the body. This study was conducted with aims to compare whole-pelvis planning in Volumetric Modulated Arc Therapy (VMAT) with boost VMAT versus Brachytherapy boost for gynecologic cancer treatment.Materials & Methods: This prospective clinical study was conducted using a convenience sampling technique involving 25 females with endometrium type intracavitary cervical cancerous tumors after hysterectomy. Each patient underwent treatment in two phases. Phase 1 entailed treating the whole pelvis with VMAT at a dose of 45 Gy. Phase 2 was administered thereafter, whereby a boost dose was added twice, each with a different technique, at a dose of 21 Gy. The first boosted technique for VMAT entailed a High-Dose-Rate (HDR) Brachytherapy. Dosimetric parameters were extracted from Dose-Volume Histograms to compare the coverage and dose-sparing of healthy tissues.Results: The mean planning treatment whole-pelvis volume was 1019.03±157.44 cm³. The Phase 1 (Ph1) plus boost VMAT delivered higher D95% dose values and D90% than Phase 1 (Ph1) plus boost HDR. The Conformity Index and homogeneity index showed that Ph1 plus boost VMAT yielded superior dose homogeneity distribution with greater conformity than Ph1 plus boost HDR, resulting in higher doses to very small target volumes. The rectal dose distribution changed between the two techniques, with the Ph1 plus boost VMAT delivering a higher biological dose. The bladder received higher D2 cm³ doses in the Ph1 plus boost VMAT technique, and the sigmoid colon received increased doses. The Ph1 plus boost VMAT yields superior dose homogeneity distribution and greater conformity than Ph1 plus boost HDR.Conclusion: The results showed differences in target coverage and organ-at-risk protection. Ph1 plus boost VMAT provided better coverage, while Ph1 plus boost HDR boosts reduced radiation exposure to organs. The boosting strategy should be personalized for optimal treatment.