Is Timing of Adjuvant Therapy Associated With Disease Recurrence in Oral Cavity Squamous Cell Carcinoma: A Single-Institution Retrospective Cohort Study.

BACKGROUND: Survival rates with oral squamous cell carcinoma (OSCC) have been unchanged for decades. Many OSCC patients receive delayed adjuvant therapy (AT) outside of the recommended 6-week postoperative window. Therefore, AT timing is potentially modifiable and may improve disease control. PURPOSE: To measure the association between AT timing and risk of OSCC recurrence. STUDY DESIGN, SETTING, SAMPLE: This is a retrospective cohort study of OSCC patients treated with surgery and AT at the Department of Oral and Maxillofacial Surgery, University of Washington from January 2009 to January 2025. Patients who did not complete AT, initiated AT >12 weeks postoperatively, developed recurrence before AT, or had less than 1 year of follow up were excluded. PREDICTOR VARIABLE: AT timing (≤6 weeks, 6 to 12 weeks). MAIN OUTCOME VARIABLE: Time to disease recurrence. COVARIATES: Demographics, social habits, surgical treatment, and disease characteristics. ANALYSES: Bivariate time-to-event analyses were performed to identify factors associated with disease recurrence. Statistical significance was set at P < .05. RESULTS: 223 OSCC patients received surgery during the study period, of whom 75 subjects were included in the final study sample. Subjects had an average age of 59.9 years (SD = 11.0) and a median follow up of 29.0 months (interquartile range [IQR] = 9.0 to 60.0). The mean time to AT was 7.9 weeks, and 17 (22.7%) of subjects received AT within 6 weeks of surgery. The rate of disease recurrence was 48.0%. Those who experienced recurrence did not have a statistically significantly longer time to AT (8.1 vs 7.7 weeks, P = .4). The median times to recurrence for ≤6 week and 6 to 12 week AT treatment groups were 8.0 months (IQR = 6.0 to 18.0) and 9.0 months (IQR = 6.0 to 22.0), respectively, and there was no statistically significant association between timely AT and disease recurrence (hazard ratio, 0.90 [0.42, 1.93], P = .8). CONCLUSIONS AND RELEVANCE: This study was unable to demonstrate an independent association between AT timing and recurrence, although a clinically meaningful effect cannot be excluded because of limited statistical power.