Radiobiology-Guided VMAT Radiotherapy Optimization for Locally Advanced Cervical Cancer

This retrospective planning study evaluated how arc number (AN) and control-point density (CP) affect VMAT quality, radiobiological endpoints, and workflow efficiency for locally advanced cervical cancer in a resource-conscious setting. Twenty-one patients (FIGO IIB–IIIB) were replanned in Monaco v5.51 (Monte Carlo) for 46 Gy using 6-MV beams (Elekta) with 1–4 coplanar arcs, and dual-arc plans were further analyzed using ≈250, 300, 350, and 400 CP per arc. Target coverage (D98/D95/V95/V98), conformity and homogeneity (CI, HI), and organs-at-risk (OARs) DVH metrics (including D2cc and Vx) were compared alongside monitor units, planning time, and delivery time. Increasing AN improved dose conformity and OAR sparing relative to single-arc plans, whereas increasing CP produced only modest dosimetric changes but substantially increased planning and treatment times. Radiobiological modeling using BED/EQD2 and EUD-based LKB NTCP indicated negligible bladder risk (<0.01%) and low rectal risk (<0.2%), but a higher small-bowel NTCP (~26%) driven by hotspot-sensitive descriptors; Niemierko TCP estimates were similar between leading dual-arc CP settings. Overall, a dual-arc strategy with ~250 CP per arc provided the most practical balance between plan quality, estimated biological effect, and deliverability.