Abstract
PURPOSE: Sparing pharyngeal constrictor muscles (PCMs) during radiotherapy improves patient-reported swallowing function. This study aimed to explore the feasibility of integrating knowledge-based planning (KBP) with multicriteria optimization (MCO) in Eclipse v18.0 to selectively spare PCM, quantify the required trade-off in prophylactic planning target volume (PTV54) coverage, and to evaluate MCO performance. METHOD: Ten patients previously planned with KBP for oropharyngeal cancer (65, 60, and 54 Gy in 30 fractions) were retrospectively re-planned. Clinical plans were further optimized using trade-off exploration in MCO, with a priority order: spinal cord and brainstem sparing, high-dose and intermediate-dose target coverage, PCM sparing, low-dose target coverage, parotids sparing, remaining organs at risk (OAR). Plans were evaluated based on planning target volumes dose metrics (D(50%), D(98%), and D(2%)), homogeneity index (HI), conformity index (CI), and maximum and mean doses to OARs, and paired t-tests were performed. Differences between navigated and deliverable plans were analyzed. One patient underwent 10 identical repeat plan generations. RESULTS: MCO reduced the average mean dose to the superior and middle PCM, inferior PCM, contralateral parotid, and larynx by 2.0, 3.4, 2.6, and 3.9 Gy, respectively (p < 0.05) but at the expense of HI and CI. No difference was observed in average PTV54 D(98%) between techniques; however, all clinical plans and seven MCO plans achieved D(98%) ≥ 95%, with three MCO plans modestly compromised (D(98%) 93.7%-94.6%). Dose metrics between navigated and deliverable plans differed by ≤0.7 Gy for mean doses and ≤1.8 Gy for maximum doses. Pareto surface generation was not repeatable. CONCLUSION: MCO effectively balances the trade-off between PCM sparing and low-dose target coverage. It may be a valuable tool in the context of personalized care.