Practice patterns and outcomes following radiation dose de-escalation for oropharyngeal cancer: A National Cancer Database analysis.

Abstract

e17508 Background: Numerous trials are evaluating radiotherapy (RT) de-escalation for HPV-mediated (HPV+) oropharyngeal squamous cell carcinoma (OPSCC). Herein, we evaluated the degree to which de-escalated RT is delivered in the United States, as well as, comparative outcomes with full-dose RT, as stratified for HPV status. Methods: We identified patients diagnosed with OPSCC in the National Cancer Database, excluding those with stage I/II disease, unknown HPV status, receiving surgery or not receiving EBRT to the primary site, receipt of radiation doses > 75 or < 54 Gy, radiation treatment course duration < 25 or > 75 days, and unknown or inadequate ( < 2 months) follow-up. Multivariable logistic regression analysis identified variables associated with delivery of de-escalated RT ( < 66 Gy). Overall survival of HPV+ and HPV- disease was compared between full-dose and de-escalated approaches. Results: Altogether, 617 and 551 patients were HPV+ and HPV-, respectively. De-escalated RT was delivered in 16.9% HPV+ and 15.2% of HPV- disease, respectively. Older patients and those not receiving systemic therapy were more likely to receive de-escalated RT. In HPV+ patients, 3- and 5-year survival rates were 83% and 80% in the de-escalated cohort versus 83% and 78% in the full-dose group (p = 0.83). In HPV- patients, corresponding 3- and 5-year survival rates were 29% and 23% versus 61% and 51% (p = 0.001). Conclusions: National utilization of de-escalated RT for OPSCC is low (15-20%), but does not seem to impact overall survival in HPV+ (but not HPV-) patients. The caveats of this heterogeneous, retrospective analysis require corroboration from a number of ongoing randomized trials.