Long-Term Outcomes After Proton Beam Therapy for Sinonasal Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is the most common sinonasal cancer and is associated with one of the poor outcomes. Proton therapy allows excellent target coverage with maximal sparing of adjacent normal tissues. We evaluated the long-term outcomes in patients with sinonasal SCC treated with proton therapy.Between 1991 and 2008, 54 patients with Stage III and IV SCC of the nasal cavity and paranasal sinus received proton beam therapy at our institution to a median dose of 72.8 Gy(RBE). Sixty-nine percent underwent prior surgical resection, and 74% received elective nodal radiation. Locoregional control and survival probabilities were estimated with the Kaplan-Meier method. Multivariate analyses were performed using the Cox proportional-hazards model. Treatment toxicity was scored using the Common Terminology Criteria for Adverse Events version 4.0.With a median follow-up time of 82 months in surviving patients, there were 10 local, 7 regional, and 11 distant failures. The 2-year and 5-year actuarial local control rate was 80%. The 2-year and 5-year rates of overall survival were 67% and 47%, respectively. Only smoking status was predictive for worse locoregional control, with current smokers having a 5-year rate of 23% compared with 83% for noncurrent smokers (P=.004). Karnofsky performance status ≤80 was the most significant factor predictive for worse overall survival in multivariate analysis (adjusted hazard ratio 4.5, 95% confidence interval 1.6-12.5, P=.004). There were nine grade 3 and six grade 4 toxicities, and no grade 5 toxicity. Wound adverse events constituted the most common grade 3-4 toxicity.Our long-term results show that proton radiation therapy is well tolerated and yields good locoregional control for SCC of the nasal cavity and paranasal sinus. Current smokers and patients with poor performance status had inferior outcomes. Prospective study is necessary to compare IMRT with proton therapy in the treatment of sinonasal malignancy.