The Effect of Treatment Time on Outcomes in Favorable-Risk Oropharyngeal Tumors Treated With Transoral Surgery Followed by Radiation Therapy

Abstract

Purpose/Objective(s): To determine the effect of treatment time on outcomes in favorable risk (majority HPV positive and/or <10 pack year smoking history) oropharyngeal squamous cell carcinomas (OPSCC) on patients (pts) treated with transoral surgery (TOS) and postoperative intensity modulated radiation therapy (IMRT). In the pre-HPV era, an overall treatment package time (from surgery to RT completion) > 100 days and a time from surgery to start of RT > 6 weeks were associated with worse outcomes in head and neck cancer pts treated with open surgery and older RT techniques. A faster postoperative recovery with TOS, the use of IMRT and HPV status may impact on treatment outcomes and the previously reported time factors may not be applicable in the modern era. Materials/Methods: A retrospective IRB approved analysis of 137 consecutive pts treated at Mayo Clinic Arizona from 2000 to 2014 with transoral laser microsurgery (TLM) and postoperative IMRT for favorable risk OPSCC. The median age was 60 years. One hundred and twenty four pts (91%) had TLM. One hundred and twenty nine pts (94%) had IMRT. Sixty seven pts (49%) received concurrent chemotherapy (CT), consisting of cisplatin in 52 (79%) pts. The majority of the pts (80%) were HPV positive. Seventy six pts (55%) had a < 10 pack year smoking history. One hundred and twenty nine pts (94%) had an ECOG performance status (PS) of 0-1. T and N stage distribution: 88% of pts had T1-T2 disease and 86% were N0-N2b. The treatment time factors considered were interval from surgery to the start of RT and treatment package time (TPT). Other variables considered were age, gender, primary site, stage, type of surgery, pathologic high risk features (margins, LVI, PNI, and ECE), HPV status, RT dose and technique, use of CT, PS and smoking history. Univariate (UA) and multivariate (MVA) (Wilcoxon test) analyses were performed. Results: The median follow-up was 24 months (range, 3 e 118 months). The median postoperative RT dose was 6000 cGy (range, 4800 e 7000 cGy). The median time from surgery to RT start was 43 days and the overall TPT was 85 days. There were no local failures and only two regional failures, resulting in 98.5% locoregional control at 4 years. Eight pts developed distant metastasis, without evidence of locoregional failure, for a 4-year overall survival (OS) of 85%. On UA, time from surgery to start of RT and TPT were not associated with a higher recurrence risk. Factors associated with worse OS in UAwere T stage (PZ0.03), PS (PZ < 0.001), smoking history (P = 0.02) and delay in the interval from surgery to the start of RT > 43 days (P = 0.03). No factors were significant on MVA. Conclusion: TLM followed by RT in favorable risk OPSCC pts results in excellent outcomes with few locoregional recurrences. Treatment time factors were not associated with a significant increase in recurrence risk. Further study in a larger cohort will help clarify the impact of treatment time.