Evaluation of Knowledge-Based Versus Manual Treatment Planning of Whole-Pelvic Volumetric Modulated Arc Therapy With Simultaneous Integrated Boost for Node-Positive Prostate Cancer

Abstract

The aim of this study is to evaluate the effectiveness and usability of knowledge-based planning (KBP) software in whole-pelvic volumetric modulated arc therapy with simultaneous integrated boost (WP-SIB-VMAT) for node-positive prostate cancer (NP-PC). A commercial KBP software was used for KBP model construction and plan optimization. Twenty-two planning data of the patients with NP-PC who had been treated with WP-SIB-VMAT in our department were used for KBP model construction. Another 32 planning data of the patients with NP-PC who had been treated with whole-pelvic fixed-gantry intensity modulated radiation therapy with SIB in our department were used for validation. The structure sets included high-, intermediate-, low-risk PTVs, and 5 organs at risk (OARs): femurs, large bowel, small bowel, bladder, and rectum. The patients were numbered according to the date of starting irradiation. Experienced medical physicist “A” and radiation oncologist “B” manually performed the optimization of WP-SIB-VMAT in patient 01-16 (Manual A), and patient 17-32 (Manual B), respectively. Resident “C” performed the optimization of WP-SIB-VMAT in patient 01-32 with use of the KBP model. He followed the rule that adjustments of optimizing objectives for PTVs with automatically generated priorities and line objectives for OARs were forbidden. For adjustment of dose to OARs, he was allowed to manually add new objectives and structures against anatomical contours. All optimizations were performed to satisfy the clinical protocol in our department. We measured the required time for optimization, and assessed the dose distributions. Two-tailed Wilcoxon signed-rank sum tests were used to identify significant (p < 0.05) differences in the required time and the mean doses to OARs. The median required time for optimization was significantly shorter in KBP than in manual planning. Similarly, except for the rectum, the median mean doses to OARs were significantly lower in KBP. The median mean dose to the rectum in Manual A plans was significantly lower than in KBP plans. Although dose coverage in protruded region of low-risk PTV, especially in obturator lymph node region, was tended to be lower in KBP plans, the dose distributions of these were considered to be clinically acceptable. No significant change was observed in KBP plans when the number of plans included in the model was increased up to 40.Abstract 3576MedianManual AKBPP valueManual BKBPP valueTime [min]48.534.0<0.0565.531.0<0.05Femurs Dmean [Gy]25.522.8<0.0525.622.7<0.05Large bowel Dmean [Gy]25.022.7<0.0525.021.7<0.05Small bowel Dmean [Gy]19.817.2<0.0521.218.5<0.05Bladder Dmean [Gy]45.343.8<0.0544.944.0<0.05Rectum Dmean [Gy]40.542.4<0.0545.142.1<0.05 Open table in a new tab Although minor manual adjustments were required to achieve the clinical goals in some cases, the KBP software generated comparable plans in significantly shorter time than manual optimization approach in WP-SIB-VMAT planning for NP-PC.