Outcomes of Head and Neck Squamous Cell Carcinomas (HNSCC) Treated with Reirradiation (RRT) at Mayo Clinic.

6064 Background: RRT is offered as definitive (DRRT) or post-operative (PRRT) treatment for patients (pts) with loco-regionally recurrent (LRR) or new primary (NP) HNSCC in previously irradiated volumes. We report the results of a retrospective chart review of all consecutive pts with LRR and NP HNSCC treated with DRRT and PRRT at Mayo Clinic. Methods: We included LRR and NP HNSCC pts treated with DRRT/PRRT from 2003-2011 at all Mayo Clinic campuses. Patient and treatment related data were collected. Loco-regional recurrence rate (LR) and distant metastases rate (DM) at 2 years, and overall survival (OS) from end of RRT using Kaplan-Meier methods, were calculated. Results: We identified 89 pts (68 M, 21 F). 67 pts had LRR; 22 NP. Treatment included salvage surgery with PRRT (47 pts) and DRRT (42 pts). 30 pts received concurrent chemotherapy (CT) with PRRT; 33 DRRT pts received CT. Median prior RT dose was 66 Gy (26.4 – 79.2 Gy). Median PRRT dose was 60 Gy (11 – 70 Gy). Median DRRT dose was 69.6 Gy (18 – 76.8 Gy). LR occurred in 42 pts (47%) after RRT; 35 pts (39%) had LR by 2 years (95% CI, 30 – 50%). DM occurred in 20 pts (22%) after RRT; 16 pts (18%) had DM by 2 years (95% CI, 11 – 27%). Median OS was 22.2 mos (95% CI, 17.0 – 29.8 mos), with 2- and 5-year OS 47% and 16%. No difference in OS between LRR- and NP-HNSCC or PRRT and DRRT was found. CT was associated with shorter time to LR (4.3 vs. 12.1 mos, p = 0.008), but not with time to distant metastases or OS. At last follow-up (median 78.1 mos) 21 pts (24%) were alive, with 43.3 mos (95% CI, 27.6 – 52.9 mos) median OS from time of LRR/NP. Among surviving pts, 2 cases of osteoradionecrosis (10%) and 1 carotid artery pseudoaneurysm with sentinel bleed (5%) were reported, with no reported spinal cord injuries. OS was better among 70 pts treated to at least 60 Gy (n = 70) vs. pts treated with less than 60 Gy (median OS 25.2 mos, 95% CI, 19.4 – 32.0 mos; vs. median OS 9.5 mos, 95% CI, 6.8 – 28.7 mos; p = 0.06). Conclusions: RRT cures a small number of pts. 2-year OS of LRR/NP HNSCC pts treated with RRT in the time frame of this study appears superior to published outcomes. Shorter time to LR among pts receiving CT warrants further study, but may signify selection bias toward more aggressive therapy for pts with high risk LRR/NP HNSCC.