GP4d - Does Timing of Adjuvant Radiation Therapy Affect Survival Among Oral Cavity Squamous Cell Carcinoma Patients?

Abstract: The effect of varying intervals between surgery and the start of postoperative radiation therapy (PORT) on oncologic outcomes remains understudied. Prior studies have investigated the timing of PORT and its impact among head and neck squamous cell carcinoma (HNSCC) patients.¹ Current guidelines from the National Comprehensive Cancer Network (NCCN) recommend starting PORT within 6 weeks of surgery for these patients to improve survival. However, the effect of timely initiation of PORT among the subset of oral cavity squamous cell carcinoma (OCSCC) patients has not been reported. The purpose of this study was to determine if starting PORT within 6 weeks of surgery versus 6 to 12 weeks improved survival among OCSCC patient.

This retrospective cohort study examined patients from 2004 to 2019 using data from the National Cancer Database (NCDB). OCSCC patients treated with curative intent surgery followed by PORT were identified. Exclusion criteria included history of prior radiation, receiving PORT >12 weeks after surgery, multiple primary malignancies, or unknown survival time. The primary predictor variable was PORT initiation timing (either within 6 weeks or at 6 to 12 weeks). Demographic data (age, gender, race, median household income), cancer-related variables (oncologic stage, tumor site) and treatment characteristics (surgical margin status, number of lymph nodes removed, radiation duration) were collected. The primary outcome was overall survival (OS). Univariate survival analyses were performed using the log rank test. A multivariable Cox proportional hazards regression analysis for overall mortality was performed using a set of demographically, clinically, and biologically pertinent predictors.

32,743 subjects were included in the study. The mean age was 59.9 (18-90) years. 66.2% were male. In the univariate survival analysis, PORT timing was significantly associated with OS when divided into 2-week (P < .001) and 6-week (P < .001) intervals. After accounting for covariates, starting PORT within 6 weeks was associated with improved OS compared to 6-12 weeks (HR 0.93, P = .037). The duration of radiation therapy did not influence OS (HR 1.00, P = .372).

The findings of this study suggest that initiating PORT within 6 weeks is associated with improved survival among OCSCC patients undergoing curative intent surgery. Once radiation was initiated, the amount of time required to complete radiation did not affect survival. Although this affirms current NCCN guidelines, further research is needed to better understand if and why other HNSCC subsites exhibit a more pronounced survival benefit with timely radiation.

1. Graboyes EM, Garrett-Mayer E, Ellis MA, et al. Effect of time to initiation of postoperative radiation therapy on survival in surgically managed head and neck cancer. Cancer. Dec 15 2017;123(24):4841-4850. doi:10.1002/cncr.30939

2. Chen, Michelle M.; Harris, Jeremy P.; Orosco, Ryan K.; Sirjani, Davud; Hara, Wendy; Divi, Vasu . (2018). Association of Time between Surgery and Adjuvant Therapy with Survival in Oral Cavity Cancer. Otolaryngology-Head and Neck Surgery, (), 019459981775167–. doi:10.1177/0194599817751679