Tumor volume reduction during adaptive radiotherapy is a strong prognostic factor for oropharyngeal cancer: A retrospective multicenter study?

Abstract

This study aimed to evaluate the prognostic significance of tumor volume reduction rate (TVRR) measured during mid-treatment adaptive radiation therapy (RT) for predicting survival outcomes in patients with oropharyngeal squamous cell carcinoma (OPSCC). This study analyzed 271 patients with OPSCC who received definitive RT, with or without concurrent systemic therapy at four institutions between 2008 and 2022. Patients underwent both pre-RT and mid-RT computed tomography simulation for adaptive re-planning. TVRR was calculated as the proportional reduction in gross tumor volume from pre-RT to mid-RT scans. A 40% threshold was applied in subsequent analyses. With a median follow-up of 53 months, the 5-year overall survival (OS) and progression-free survival (PFS) were 85.4% and 74.8%. Patients with TVRR > 40% achieved superior 5-year OS (90.9% vs. 77.9%, p = 0.003) and PFS (79.0% vs. 68.5%, p = 0.039) compared with those with TVRR ≤ 40%. On multivariate analysis, TVRR > 40% was independently associated with improved OS (HR = 0.432, 95% CI: 0.221-0.846, p = 0.014). Subgroup analysis showed prognostic value of TVRR primarily in HPV-positive patients. TVRR may serve as a useful prognostic indicator in patients with OPSCC treated with definitive RT and could help stratify patients by risk for treatment de-intensification or intensification. While prospective validation is still needed, TVRR has strong potential to enhance personalized RT and improve the treatment outcomes in patients with OPSCC.