The influence of treatment facility volume on the mortality of multiple myeloma patients.
284 Background: MM is an uncommon cancer with annual incidence of only 27,000 cases in the US. Our study determined the extent to which the number of MM patients treated annually in a treatment facility affected all-cause mortality. Methods: We used the National Cancer Data Base (NCDB) to identify adult patients with MM diagnosed from 2003-2011. NCDB is sourced from over 1,500 Commission on Cancer-accredited cancer registries representing 70% of cancer cases in the US. We classified treatment facilities by quartiles based on facility volume (mean patients/year): Quartile 1 (Q1: < 3.6), Quartile 2 (Q2: 3.6-6.1), Quartile 3 (Q3: 6.1-10.3) and Quartile 4 (Q4: > 10.3). We used hot deck imputation to account for missing data, Cox regression to analyze the association between facility volume and time-to-death, and random intercepts to adjust for multiple patients per facility. Results: There were 94,722 MM patients cared for at 1,333 facilities. Most patients (73.5%) were diagnosed and treated in the same facility. The median age at diagnosis was 67 years and 54.7% were males. The median annual facility volume was 6.1 patients/year (IQR: 3.6-10.3; range: 0.2-109.9). The distribution of patients according to facility volume was Q1 (5.2%), Q2 (12.6%), Q3 (21.9%) and Q4 (60.3%). The unadjusted median overall survival by facility volume was: Q1: 26.9 months, Q2: 29.1 months, Q3: 31.9 months and Q4: 49.1 months. After multivariable analysis adjusting for demographic (sex, age, race, ethnicity), socioeconomic (income, education, insurance type), geographic (area of residence, treatment facility location), co-morbidity (Charlson-Deyo score), and disease-specific (year of diagnosis) factors, we show that facility volume remains an independent predictor of all-cause mortality. Compared to patients treated at Q4 facilities, patients treated at lower quartile facilities had a higher risk of death (Q3 HR: 1.16 [95% CI, 1.12-1.20]; Q2: 1.21 [1.17-1.26]; Q1: 1.27 [1.22-1.34]). We observed an inverse volume-outcome relationship up to an annual facility volume of approximately 60 patients. Conclusions: MM patients treated at higher volume facilities had lower risk of mortality compared to those treated at lower volume facilities.