Impacts of Oropharyngeal Cancer PTV Coverage Prescription Levels on Clinical Outcomes
Poster
NBH_AAPM 2026 Poster.pdf Hosted by AAPM · 0.5 MBAbstract
Purpose
Definitive radiotherapy for oropharyngeal cancer (OPC) requires adequate PTV coverage, but the optimal degree of target coverage is unknown. Some protocols require a PTVD95≥95% whereas others require PTVD95≥100% of prescription dose. Prescribing higher PTV dose coverage (i.e. PTVD95≥100%) may improve cancer control but requires trade-offs in healthy-tissue dose potentially increasing radiation-related toxicities. Quantitative evidence is limited on whether radiotherapy prescribed to PTVD95≥100% improves overall survival (OS) or recurrence. This retrospective study evaluates the difference in treatment outcomes for OPC patients prescribed to PTVD95≥95% or 100%.
Methods
Patients were identified using existing databases of OPC patients treated with radiotherapy. For this analysis, we pooled two databases, one from 2010-2019 and the other from 2022-2025 for a total of n=404 patients (median age: 61 years) treated with 70 Gy/35fx. Patients were stratified by PTV prescription dose, with all patients having a 5 mm expanded PTV margin. Kaplan-Meier analysis was used with the log-rank test to assess significance.
Results
101(25%) patients were prescribed to PTVD95≥95%, and 303(75%) prescribed to PTVD95≥100%. 306(76%) patients were HPV-positive, 60(15%) HPV-negative, 39(10%) were indeterminate. The proportion of Stage I, II, III, IV patients were 76(18%), 140(35%), 92(23%), and 96(24%) respectively. Analyses compared OS and recurrence between the PTVD95≥95% and PTVD95≥100% groups (median follow-up of 3.9 years; 95% CI [3.3, 4.1]). The five-year OS was 75.6% and 71.7% for PTVD95≥95% and 100%, respectively. No statistically significant difference in OS was found between those prescribed to PTVD95≥95% and 100% (p=0.399). The likelihood of recurrence was not significantly different between the prescription groups (p=0.359), following the five-year follow-up.
Conclusion
Delivery of 100% of the prescription dose to 95% of the target volume (PTV) did not significantly alter the cancer outcomes when compared to the standard of care (PTVD95≥95%) in a large cohort of OPC patients treated with definitive radiotherapy.