RapidArc Dynamic versus IMRT and VMAT for Endometrial Cancer SIB Radiotherapy

Background Radiotherapy with simultaneous integrated boost (SIB) for endometrial cancer requires highly conformal dose distributions to reduce toxicity. RapidArc Dynamic (RAD), a novel technique combining dynamic arc delivery with strategic gantry pauses, may improve organ-at-risk (OAR) sparing and efficiency. Purpose By comparing RAD with conventional IMRT and VMAT for endometrial SIB radiotherapy, evaluating OAR sparing and treatment efficiency of RAD technique in endometrial cancer treatment. Methods and Materials : Thirty patients with high-intermediate risk endometrial cancer were retrospectively enrolled. Three plans (RAD, IMRT, VMAT) were generated per patient, prescribing 50.4 Gy to the planning target volume (PTV) and 61.6 Gy to the nodal clinical target volume (CTVn) in 28 fractions. Plans were evaluated for OAR dose constraints, conformity index (CI), inward-outward dose gradient ratio (IOR), monitor units (MU), and modulation complexity score (MCS). Results RAD plans demonstrated superior OAR sparing, with significantly fewer and less severe constraint violations for the bladder, rectum, small intestine, and bone marrow compared to IMRT and VMAT (Mann-Whitney U test, P < 0.05). RAD achieved a significantly higher CI than VMAT and a steeper inward dose gradient than both IMRT and VMAT. RAD also used significantly fewer MU than IMRT and exhibited higher MCS, indicating less complex delivery. Conclusions RAD provides superior OAR protection and steeper dose fall-offs compared to IMRT and VMAT, while maintaining high target dose conformity and improving delivery efficiency. It represents a highly promising technique for endometrial SIB radiotherapy, combining the advantages of IMRT and VMAT.