92.9%, and MRI in 7.4% to obtain precise size, location, number, and extent of primary and nodal involvement. Outcomes, including local control (LC), regional control (RC), and freedom from distant metastases (FFDM), were estimated via Kaplan-Meier method and comparisons made via log-rank test. Results: Median follow-up of patients alive at last contact was 29 months. All patients were treated with definitive RT alone (n Z 49, 15.9%) or concurrent systemic therapy and RT (n Z 260, 84.1%). LC was seen in 301 of 309 patients, for a 3 year LC rate of 97.1%. LC was less likely in patients with retropharyngeal lymph node involvement (P Z 0.012), 5 or more lymph nodes involved (0 vs. 1-4 vs. 5, P Z 0.029), or primary tumor >4cm (P Z 0.052). RC was achieved in 295 of 309 patients (94.6% at 3 years). RC was less likely if there was retropharyngeal lymph node involvement (P Z 0.042), nodal tumor size >6cm (N0 vs. 6cm vs. >6cm, P Z 0.028), 5 or more nodes (0 vs. 1-4 vs 5, P Z 0.015), or if a lymph node was present in level 4 or 5 (N0 vs. level 3 or above vs level 4 and below, P Z 0.036). Distant metastases occurred in 27 patients, for a 3 year FFDM rate of 90.5%. Lower rates of FFDM was associated bilateral lymphadenopathy (N0 vs. unilateral vs bilateral, P Z 0.031), 5 or more nodes (0 vs. 1-4 vs 5, P < 0.001), or if a lymph node was present in level 4 or 5 (N0 vs. level 3 or above vs level 4 and below, P < 0.001). Conclusion: Outcomes for patients with HPV associated oropharyngeal cancer treated with definitive RT are excellent. Increasing burden of adenopathy, either by size or number, or location in level 4 or 5 predicted for a higher risk of regional failure or metastasis. These factors may provide a basis for altering staging.
