Reevaluation of postoperative radiation dose in the management of human papillomavirus-positive oropharyngeal cancer.

Background The purpose of this study was to compare outcomes of patients with p16-positive oropharyngeal squamous cell carcinoma (SCC) treated with postoperative intensity-modulated radiotherapy (IMRT) before and after an institutional dose reduction policy effective on February 2009. Methods Between 1998 and 2013, 175 consecutive patients with p16-positive oropharyngeal SCC with extracapsular extension (ECE) and/or close or positive margins were treated postoperatively to 66 Gy (n = 109) or 60 Gy (n = 66) in 2 Gy/fx. Results Between the 66 and 60 Gy groups, there was no difference in tumor classification (pT4 vs pT1–T3; p = .181) and nodal classification (pN2c–N3 vs pN0–N2b; p = .704), and American Joint Committee on Cancer (AJCC) group stage (IV vs I–III; p = .473). Median follow-up was 5.9 years overall (66 Gy: 7.4 years; 60 Gy: 4.0 years). There was no difference in locoregional recurrence-free survival (2-year: 98.1% vs 98.5%; p = .421). Conclusion This study suggests that treating p16-positive oropharyngeal SCC with ECE and/or close or positive margins with postoperative IMRT to 60 Gy may not compromise locoregional recurrence-free survival compared to 66 Gy. © 2016 Wiley Periodicals, Inc. Head Neck 38: 1708–1716, 2016