Predictors of Ability to Complete Prescribed Concurrent Cisplatin Chemotherapy Regimen and Effect on Outcomes in Oropharyngeal Head and Neck Cancer Patients Treated With Radiotherapy.

PURPOSE/OBJECTIVE(S) The addition of cisplatin to radiation therapy (RT) results in improved outcomes in oropharyngeal head and neck cancer (OHNC) patients. This comes at the cost of increased toxicities over RT alone and often results in the inability to complete the initially prescribed chemotherapy regimen. In this study, potential predictors of chemotherapy completion and their effect on outcomes were investigated in OHNC patients treated at two different institutions. MATERIALS/METHODS We conducted a retrospective chart review of patients with OHNC at two different institutions. Patients were staged according to AJCC 8th Ed and separated into two groups: Completers (able to complete initially prescribed concurrent cisplatin regimen) and Non-Completers (unable to complete all prescribed cycles and/or required change to a different systemic therapy agent). Age, sex, race, ECOG, smoking status, HPV status, and stage were analyzed for ability to predict completion of chemotherapy regimen and for prognostic implication on outcomes. Overall survival (OS) and local control (LC) were calculated from start of RT. Chi-squared was used for associations, Kaplan-Meier estimates were compared using log-rank test, odds ratios (OR) and hazard ratios (HR) were generated from logistic and Cox regression analyses, respectively. RESULTS Between 2007 and 2019, 271 patients with OHNC were reviewed and included in the study. Most patients were Stage II (60%) and HPV positive (83%). More patients were Completers (61%) than Non-Completers (39%). Mean age was 56.6 years in Completers and 58.0 years in Non-Completers. Comparing Stage I to IV was the only significant predictor of chemotherapy completion (OR 6.139, 95% CI 1.43-26.35). HPV negative status trended towards significance for non-completion (OR 0.520 P = 0.061). Predictors of inferior OS were race (Non-White vs White) HR 2.520 P = 0.001; ECOG (2-3 vs 0-1) HR 2.324 P = 0.018; ever smoker (Yes vs No) HR 2.582 P = 0.001; HPV status (Negative vs Positive) HR 3.584 P < 0.001; and Stage (IV vs I) HR 5.983, 95% CI 1.38, 25.97. Inability to complete chemotherapy was not found to be a predictor of inferior survival (HR 0.737 P = 0.173). OS at 3 years was not statistically different between Completers (81%) and Non-Completers (77%), P = 0.404. LC at 3 years was not statistically different between Completers (93%) and Non-Completers (92%), P = 0.755. CONCLUSION In our study of OHNC patients who were mostly HPV positive and early stage, cancer stage was found to be the only significant predictor of chemotherapy completion. Chemotherapy completion was not found to be a predictor of outcome. Provided the Non-Completer group included those who had a change in systemic agent but may have completed the same total number of planned chemotherapy cycles, this study suggests the need for further multivariate analysis and potentially more upfront individualized chemotherapy regimens.