Disparities in Initial Thyroid Cancer Care by Hospital Treatment Volume: Analysis of 52,599 Cases in California.

BACKGROUND Racially minoritized patients with thyroid cancer are less likely to receive high-quality and guideline-concordant care. Inaccessibility of high-volume centers may contribute to inequalities in thyroid cancer outcomes. This study sought to understand the extent to which access to higher volume thyroid cancer centers is associated with patient outcomes. METHODS We queried linked California Cancer Registry and California Office of Statewide Health Planning and Development databases for thyroid cancer patients who received thyroid surgery between 1999-2017. Hospitals were stratified by their median annual volume of thyroid cancer operations: ultra-low volume (0-5 cases/year), low-volume (6-25 cases/year), mid-volume (26-50 cases/year) and high-volume (>50 cases/year). We analyzed the rates of complications, rates of reoperation for cancer recurrence, use of radioactive iodine, and mortality by median hospital volume of thyroid surgery. A multivariable regression controlled for high-risk tumor features. Differences in access by center volume were assessed based on patient demographics. RESULTS We studied 52,599 thyroid cancer patients who underwent thyroidectomy. Patients who underwent thyroidectomy at ultra-low volume centers were more likely to undergo reoperations for recurrent/persistent disease compared to patients at low- (odds ratio [OR] 1.17, 95% confidence interval [CI] 1.02-1.35), mid- (OR 1.25, CI 1.06-1.46), and high-volume centers (OR 1.26, CI 1.03-1.56). Patients who received thyroid operations at ultra-low volume centers were also less likely to receive guideline-concordant radioactive iodine ablation compared to patients at higher-volume centers (OR 0.77, CI 0.72-0.82). A pair-wise comparison between all volume categories for all outcomes revealed no statistically significant differences in outcomes between low, mid, or high-volume centers. Only ultra-low volume centers had significantly higher rates of adverse outcomes. Ultra-low volume centers were disproportionately accessed by women (p<0.05), Hispanic, Asian/Pacific Islander, and American Indian people (p<0.01), those from the lowest three quintiles of socio-economic status (p<0.01), and the uninsured and those on Medicaid or Medicare (p<0.01) when compared to higher-volume centers. CONCLUSIONS Patients receiving thyroid cancer surgery at centers performing < 5 such operations per year were more likely to require reoperation for recurrent/persistent disease and less likely to receive appropriate radioactive iodine ablation. Ultra-low volume centers served higher proportions of socially and economically marginalized communities.