Dosimetric comparison of coplanar and noncoplanar volumetric modulated arc therapy for ovarian-sparing cervical cancer radiation therapy

Cervical cancer radiotherapy in young patients risks premature ovarian failure. Ovarian-sparing techniques (OS-CRT) are critical for preserving fertility and endocrine function, yet optimal planning strategies remain underexplored. To compare dosimetric outcomes, efficiency, and plan quality between coplanar (C-VMAT) and non-coplanar VMAT (NC-VMAT) using two treatment planning systems (TPS): Monaco (Elekta Infinity) and uRT-TPOIS (uRT-linac 506c). Four plans (MC-CVMAT, MC-NCVMAT, UT-CVMAT, UT-NCVMAT) were designed for 20 cervical cancer patients with bilateral ovarian transposition. Dosimetric parameters (PTV D0.03 cc, Dmean, HI, CI; ovarian Dmax/Dmean), plan complexity (modulation complexity score, MCS), delivery efficiency (beam-on time, BOT; monitor units, MU), and plan quality metrics (PQM) were evaluated. Statistical analysis included ANOVA and non-parametric tests. All plans met clinical constraints. NC-VMAT showed marginally lower PTV D0.03 cc (48.45 ± 0.48 Gy vs. 48.71 ± 0.38 Gy, p = 0.063) and improved bowel bag Dmean (20.0 ± 2.3 Gy vs. 24.1 ± 3.5 Gy, p < 0.001) but increased BOT (114s vs. 86s for uRT-TPOIS; 233s vs. 193s for Monaco). C-VMAT demonstrated superior efficiency (optimization time: 15–40 min) and lower complexity (MCS = 0.335 vs. 0.222 for NC-VMAT). uRT-TPOIS achieved better CI (0.89 vs. 0.87, p < 0.001) and bowel sparing, while Monaco reduced bladder/rectal D2cc (47.27 ± 0.39 Gy vs. 47.52 ± 0.32 Gy, p < 0.05). No significant differences in PQM were observed. C-VMAT is preferred for OS-CRT due to balanced efficiency and dosimetry. uRT-TPOIS excels in rapid optimization and image guidance, whereas Monaco offers superior OAR protection. These findings provide clinically actionable insights for ovarian function preservation.