3663 - Outcomes Following Implementation of 50 Gy Postoperative Radiation for Intermediate-Risk HPV-Associated Oropharyngeal Cancer
Presenter(s)
L. Williams1, J. Hintze1, A. Esce1, Y. Wu1, S. M. McBride2, D. Y. Gelblum2, I. Ganly3, J. Shah4, B. Givi1, S. Patel3, J. Cracchiolo3, M. Cohen3, N. Riaz2, Y. Yu2, A. Shamseddine2, A. Ho1, R. J. Wong3, and N. Y. Lee2; 1Memorial Sloan Kettering Cancer Center, New York, NY, 2Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 3Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, 4Memorial Sloan Kettering Cancer Center, Department of Head and Neck Surgery, New York, NY
Purpose/Objective(s):
The phase II ECOG-ACRIN 3311 trial evaluated a risk-stratified postoperative radiation therapy (RT) paradigm following transoral surgery (TOS) for HPV-associated oropharyngeal squamous cell carcinoma (HPV+OPSCC). In intermediate-risk patients, adjuvant 50 Gy vs 60 Gy achieved similar progression-free survival (PFS). We subsequently adopted 50Gy for intermediate risk patients and here compare oncologic and toxicity outcomes in these patients to a pre-2022 cohort treated with 60 Gy.
Materials/Methods:
Consecutive patients with intermediate-risk HPV+OPC who received 50 or 60 Gy adjuvant RT (2015-2025) following transoral resection with neck dissection were identified. The primary endpoint was 2-year PFS. Secondary endpoints included locoregional control, distant metastasis, and toxicity (CTCAE v5.0).
Results:
Of 35 patients receiving 50 Gy adjuvant RT, 48.6% were pT1; 45.7% pT2; 5.7% pT3; 8.6% were pN0 and 91.4% were pN1. Of 54 patients receiving 60 Gy, 3.7% were pT0; 55.6% pT1; 38.9% pT2; 1.8% pT3; 5.6% were pN0; 94.4% pN1.
In the 50Gy cohort, at median follow up of 31 months, there were 2 recurrences, both distant metastases (lung), and no locoregional recurrences. In the 60Gy cohort, at median follow up 71.1 months, there was 1 local recurrence and 3 distant metastases.
The 2-year PFS for the 50 Gy group was 94.1% (95% CI 78.4-98.5) and 2-year OS was 100% (95% CI: 91.4-100), comparable to the 50 Gy arm of ECOG 3311. Outcomes were similar in the 60 Gy group, with 2-year PFS of 94.4% (95% CI 83.7-98.2) and 2-year OS of 98.2% (95% CI: 87.6-99.7).
There was a non-statistically significant higher rate of acute grade =3 toxicity in the 60 Gy vs 50 Gy group (14.8% vs 5.7%, p=.18). The rate of late grade =3 toxicity was low in both groups (1.8% vs 0%). There were 3 cases (5.6%) of osteoradionecrosis in the 60 Gy group, and zero in the 50 Gy group.
Conclusion:
In this single-institution cohort of intermediate-risk patients with HPV+OPSCC, a risk-adapted, reduced-dose postoperative RT strategy consistent with the framework established in ECOG 3311 was associated with favorable oncologic and toxicity outcomes. Although the observed toxicity rates between 50 Gy and 60 Gy were not statistically different, longer follow-up may reveal divergence, as late radiation-related effects can manifest years after treatment.