Association of social vulnerability with delays in starting guideline-adherent adjuvant therapy among patients with head and neck cancer

6523 Background: For patients with head and neck squamous cell carcinoma (HNSCC), initiation of postoperative radiation therapy (PORT) within 6 weeks of surgery is recommended by NCCN Guidelines and is the only Commission on Cancer Quality Metric for HNSCC due to the robust association of PORT delays with mortality and recurrence. Prior studies have identified that racial and ethnic minority and underinsured patients are at increased risk for PORT delay. However, no studies have examined the role of social vulnerability (i.e., social determinants of health such as education, housing, and transportation) in explaining disparities in PORT delay. To address this gap, this study seeks to evaluate the association of social vulnerability with delays in starting guideline-adherent PORT for patients with HNSCC. Methods: This is a multicenter retrospective cohort study of adult patients with HNSCC undergoing surgery at 3 urban academic centers followed by adjuvant therapy from 2018-2020. The primary outcome was delay in initiating guideline-adherent PORT (i.e., > 6 weeks [42 days] postoperatively). Time-to-PORT (TTP) was analyzed as a secondary outcome. Census-tract level Social Vulnerability Index (SVI) scores were calculated as a national percentile rank (0 to 1) with higher scores indicating greater social vulnerability. Multivariable logistic regression (MLR) was used to evaluate the association of SVI with PORT delay. Kaplan-Meier curves and a log-rank test were used to evaluate differences in TTP between patients in the highest social vulnerability quartile (SVI > 0.75) vs those in the lowest social vulnerability quartile (SVI ≤ 0.25). Results: The study included 505 patients undergoing surgery and adjuvant therapy. The mean age was 62.1 ± 11.9 years; 71% were male, 14% were Black and the most common tumor subsite was oral cavity (61%). The rate of PORT delay was 52% (95% CI 48-57%). Median TTP was 43 days (IQR 35-55 days). The mean overall SVI score was 0.48 ± 0.27. An increase in SVI of 0.25 was associated with a 33% increase in the odds of PORT delay (OR=1.33, 95% CI=1.08 to 1.63; p=0.0067) on MLR adjusted for facility, age, race, ethnicity, health insurance status, cancer subsite, rurality, and distance to the surgical facility. Patients in the highest SVI quartile had a significant increase in TTP relative to those in the lowest SVI quartile (log-rank p=0.012; median TTP = 47 and 42 days, respectively). Conclusions: In this multi-institution study, over half of patients with HNSCC experience delays in starting PORT. Increased census-tract level social vulnerability is associated with a greater risk of delayed initiation of guideline-adherent PORT. These data can be used to: 1) enhance existing risk prediction models and identify patients at-risk for PORT delay who might benefit from a targeted intervention and 2) improve institutional level risk-adjustment for case mix.