Trends in survival after treatment for breast cancer at high-volume centers: An update from the National Cancer Database (2007-2017).

274 Background: Breast cancer accounts for 30% of female cancers in the United States, resulting in many women undergoing treatment in their communities. Regionalization in cancer care organizes complex oncology treatment towards high-volume centers of excellence, yet barriers to equitable access remain. We sought to determine patient factors and disease characteristics associated with greater survival benefit from high-volume care, and those for whom this may not be necessary. Methods: We queried the National Cancer Database (2007-2017) for individuals who underwent surgery for stage 0-III breast cancer. Using restricted cubic spline methodology, we modeled the relationship between rolling annual facility-level breast surgical volume and adjusted hazard of overall survival to identify volume thresholds associated with improved overall survival. We compared patient-level characteristics across the high- vs low-volume threshold and performed an adjusted survival analysis with interaction terms for factors including demographics, socioecological factors, and disease characteristics to assess for effect modification. Results: Overall, 308,271 individuals with stage 0-III breast cancer were identified. 99.2% of whom were female and 74.4% of whom were non-Hispanic White. A survival benefit in the volume-outcome relationship was noted at the inflection point of 201 cases per year, differentiating “high-volume” from “low volume” centers. The adjusted hazard ratio HR of overall mortality for utilizing a high-volume center was 0.86 (95% confidence interval CI 0.85, 0.88). Characteristics that demonstrated an interaction with surgical volume and survival included tumor grade well-differentiated HR 0.80 (95% CI 0.75, 0.84); moderately-differentiated HR 0.73 (95% CI 0.70, 0.75); poorly-differentiated HR 0.89 (95% CI 0.86, 0.92), hormone receptor status ER+/PR+/HER2- HR 0.84 (95% CI 0.81, 0.87); HER2+ HR 0.69 (95% CI 0.64, 0.74); ER-/PR-/HER2- HR 0.92 (95% CI 0.86, 0.98), and patient age 18-54 years HR 0.91 (95% CI 0.86, 0.95); 55-69 years HR 0.84 (95% CI 0.81, 0.87); 70-89 years HR 0.88 (95% CI 0.84, 0.90). Notably, neither patient comorbidities nor distance traveled to the treating facility were associated with a different degree of improvement in survival at high-volume centers. Conclusions: Breast cancer treatment at high volume centers remains associated with an improved overall survival for all women, regardless of patient demographics and disease. Further research is needed to identify individuals from across common cancer types, as well as aspects of respective multidisciplinary treatment, where the benefits of regionalized care outweigh the burden to patients and families.