Exploration of overlap volumes-based IMRT Rapidplan for cervical cancer patients with the aim of OARs sparing

Purpose: Developing a novel overlap volumes-basedRapidPlan model for cervical cancer radiotherapy, aiming to spare organs at risk (OARs). Methods: A retrospective analysis was conducted on 110 cases of cervical cancer patients. We utilized the planning target volume (PTV) and two organs at risk (OARs): bladder and bowelbag, as the primary protocol standards for planning. Original and unclassified dose-volume histogram (DVH) estimation models (Model-O) were trained using 80 initial plans, there are 40 cases in RMS and RML respectively. The classification criteria used the ratio of bladder volume overlapping with PTV to total bladder volume, and the ratio of bowelbag volume overlapping with PTV to total bowelbag volume. Based on the sum of these volume ratios (SVR), with thresholds of ≤0.4 and >0.4, new training sets and DVH estimation models were generated, named Model-S and Model-L respectively. The plans created using Model-O were named UMO, those configured with Model-S were referred to as RMS, and the plans configured with Model-L were called RML. An analysis of dosimetric parameters for the PTV and OARs was conducted for the three automated plans. Results: For 15 patients with SVR ≤ 0.40, UMO, RMS, and RML automatically produced clinically acceptable plans. Comparing UMO and RML, RMS reduced the high-dose region V47.25 (V105%) for the PTV and provided greater dose sparing in the Bladder and Bowelbag. In cases where SVR exceeded 0.40, the mean PTV coverage with RMS only 94.9%. Comparing to UMO, RML showed greater dose sparing for the Bladder, Bowelbag, Bladder overlap, and Bowelbag overlap, as well as improved V100% of the PTV. Conclusions: The results indicate that employing overlap volumes-based IMRT Rapidplan enhances sparing of OARs when dealing with significant overlap between PTV and OARs.