Knowledge-Based Treatment Planning Model Improves Organ-at-Risk Sparing and Plan Consistency across Clinics for Prostate Radiation Therapy

Abstract

<h3>Purpose/Objective(s)</h3> The quality of volumetric modulated arc therapy (VMAT) plans highly depends on the planner's preference and experience. A commercially available knowledge-based planning (KBP) module has been widely implemented to estimate the patient-specific optimal dose-volume histogram and enable semi-automatic treatment planning. The purpose of this study was to investigate whether the KBP clinical implementations have improved organ-at-risk (OAR) sparing and plan quality consistency across clinics within our institution for prostate cancer VMAT treatments. <h3>Materials/Methods</h3> A cohort of 1,484 prostate cancer VMAT treatment plans delivered across three different clinics within our institution from January 2016 to January 2022 were retrospectively identified. The prescription (Rx) schemes of 45 Gy and 70 Gy were selected for statistical investigations since these were the only Rx schemes containing more than 50 VMAT plans created with KBP models. Dosimetric parameters of the bladder, rectum, left/right femoral heads, penile bulb, and volume ratio of 50% isodose line to PTV (R50) were extracted. <h3>Results</h3> Since its first adoption in the last quarter of 2018, KBP planning remained at a low application rate from 0% to 20.0% in each quarter. After publishing KBP models clinically at the beginning of 2021, the application rate of prostate KBP models raised to levels from 53.5% to 71.0% in each quarter. For the 70 Gy Rx scheme, parameters of R50 (w/ KBP: 3.67±4.35 vs w/o KBP: 4.17±6.25, <i>p</i>=0.009), bladder (V_40Gy: 25.49%±13.02% vs 30.50%±16.52%, <i>p</i>=0.002; D_mean: 26.47±9.17 Gy vs 30.51±10.11 Gy, <i>p</i>=0.003) and rectum (V_45Gy: 17.45%±9.25% vs 25.23%±10.40%, <i>p</i><0.001; D_mean: 25.41±5.97 Gy vs 30.59±6.77 Gy, <i>p</i><0.001) were all statistically significantly improved with KBP planning. For the 45 Gy Rx scheme, the results were consistent with the 70 Gy Rx scheme. Across the three different clinics, the investigated parameters became more consistent after the adoption of KBP planning (e.g., bladder D_mean in Gy, w/ KBP: 27.52±10.21, 26.47±9.15 and 31.10±9.83 for clinic 1, 2 and 3, respectively, <i>p</i>₁₂=0.646, <i>p</i>₁₃=0.276, <i>p</i>₂₃=0.453; w/o KBP: 28.03±12.52, 27.02±13.97 and 39.85±23.27 for clinic 1, 2 and 3, respectively, <i>p</i>₁₂=0.425, <i>p</i>₁₃<0.001, <i>p</i>₂₃<0.001). This indicates that, with KBP implementations, we have achieved improved OAR-sparing across the institution as well as increased levels of plan quality standardization. <h3>Conclusion</h3> This study demonstrated that KBP models could improve OAR sparing and plan quality consistency across clinics for prostate VMAT radiation therapy. Clinical adoptions of KBP could potentially reduce inter-planner variations and facilitate the standardization of VMAT treatment planning.