Decreased Radiation Dose to Swallowing Organs at Risk (Pharyngeal, Laryngeal, and Oral Cavity Structures) by “Tongue-Out” Compared to Tongue-In Position During Intensity-Modulated Radiation Therapy for Base of Tongue Cancer

Abstract

Between 12/1989 and 4/2011, we reviewed 425 patients with non-metastatic oral cavity cancer were treated with postoperative RT at our institution: 301 patients received adjuvant RT while 124 received salvage RT after tumor recurrence and salvage surgery. We estimated overall survival (OS) for the adjuvant cohort using the KM method for OS and cumulative incidence of LF, LRF, and DM using the Gray method. We subsequently performed a landmark analysis from 12 months post the initial surgery to reduce immortal time bias and compare the same outcomes in the adjuvant versus salvage cohort using the Cox proportional hazards regression model and Fine and Gray competing risks method. Results: The adjuvant cohort had significantly higher T stage than the salvage cohort, T1: 23% vs 66%; T2: 34% vs 23%; T3: 9% vs 3%; T4: 34% vs 2% p<0.0001. The adjuvant cohort also had significantly more locally advanced N stage than the salvage cohort, N0: 33% vs 93%; N1: 25% vs 2%; N2: 41% vs 3%, N3: 1% vs 0%. The median follow up for survivors was 77 months from the landmark, the 5 year LF, LRF, DM, and OS rates in the adjuvant cohort were 21.8%/28.7%/19%,/57% respectively. On MVA, patients who received salvage RT experienced significantly poorer OS compared to those that received adjuvant RT after adjusting for age and T stage (HR 1.84, 95% CI 1.26-2.70, pZ0.002). Salvage RT was also associated with significantly lower rates of LRC (HR 1.56, 95% CI 1.18-2.06, pZ0.002) and DM (HR 1.53, 95% CI 1.08-2.17, pZ0.02) on MVA. Conclusion: Salvage RT when adjusted for other factors results in significantly decreased LRC, higher rates of DM, and decreased OS as compared to adjuvant RT in OCC. Our study suggests that aggressive upfront loco-regional therapy represents the best opportunity to cure oral cavity carcinoma.