Referral patterns between high- and low-volume centers and associations with uterine cancer treatment and survival: a population-based study of Medicare, Medicaid, and privately insured women

Background: High-volume center surgery and gynecologic oncology care are associated with improved outcomes for women with uterine cancer. Referral patterns, from biopsy through to chemotherapy, may have patients interacting with high-volume centers for all, a portion, or none of their care. The relative frequency, the underlying factors that contribute to referral, and the potential impact of these referral patterns on treatment outcomes are unknown.

Objective: We sought to analyze the referral patterns and subsequent impact of care sites on treatment for women with high- and low-risk uterine cancer.

Study design: This is a population-based retrospective cohort study of uterine cancer cases from 2004 through 2009 in North Carolina. Using state cancer registry files linked to Medicare, Medicaid, and private payer insurance claims, we analyzed referral and treatment patterns by annual surgical volume (high ≥12/y). We examined clinical and demographic factors associated with referral and used modified Poisson regression to evaluate risk of referral, lymphadenectomy, and chemotherapy. Stratified Kaplan-Meier plots and Cox proportional hazard models were used to examine survival.

Results: A total of 2053 women were analyzed, including 34% (n = 677) with grade 3 histology. Of 1630 (80%) women with preoperative biopsies, referral patterns (biopsy to surgery) were: low volume to high volume (n = 652, 40%), followed by high volume to high volume (n = 605, 37%), then low volume to low volume (n = 318, 20%), and the rare high volume to low volume (n = 50, 3%). Women retained in low-volume centers after biopsy were older, were less likely to have private insurance, and had more comorbidities. High-risk histology (aRR, 1.14; 95% confidence interval, 1.04-1.25) was positively associated with referral, while Medicaid insurance was negatively associated with referral (aRR, 0.64; 95% confidence interval, 0.42-0.96). Most women (74%, n = 1557) had surgery at high-volume centers. Lymphadenectomy was less likely at low-volume centers (aRR, 0.71; 95% confidence interval, 0.64-0.77). Similarly, for high-risk patients, the relationship between low-volume center surgery and subsequent chemotherapy was aRR, 0.71 (95% confidence interval, 0.48-1.02). Of 290 women who received chemotherapy, the referral patterns (surgery to chemotherapy) were: high volume-all (high volume to high volume), high volume-hybrid (high volume to low volume, or low volume to high volume), and high volume-none (low volume to low volume). In all, 36% (n = 104/290) received chemotherapy at a low-volume center, the majority (68%, n = 71/104) of whom were referred from high-volume centers after surgery. Crude, unadjusted mortality risk of chemotherapy recipients differed by referral pattern (surgery to chemotherapy): high volume-all patients (hazard ratio, 1.0; referent), followed by high volume-hybrid (hazard ratio, 1.33; 95% confidence interval, 0.93-1.91) then high volume-none patients (RR, 1.95; 95% confidence interval, 1.24-3.08).

Conclusion: Most women with uterine cancer treated at high-volume centers arrive through referral, which is affected by age and type of insurance, in addition to histology. For high-risk women who require chemotherapy, survival may be related to the extent of treatment received at high-volume centers.