Prior studies have shown that a higher hospital volume or physician caseload is associated with better outcomes for complex and uncommon surgical procedures. Similar studies in the medical management of rare diseases such as hematologic cancers are limited. This retrospective, observational study using the US National Cancer Data Base determined the extent to which the number of new non-Hodgkin lymphoma (NHL) patients treated annually at a treatment facility affected overall survival (OS).METHODS:
There were 278,985 patients treated at 1151 facilities from 1998 to 2006. Treatment facilities were classified by quartiles based on the average number of new NHL patients seen annually: quartile 1 (Q1), 2 to 13 patients; quartile 2 (Q2), 14 to 20 patients; quartile 3 (Q3), 21 to 32 patients; and quartile 4 (Q4), 33 or more patients. The outcome of interest was OS according to facility volume.RESULTS:
The unadjusted median OS was 61.8 months for Q1, 65.9 months for Q2, 71.4 months for Q3, and 83.6 months for Q4. A multivariate analysis that was adjusted for demographic (sex, age, race, and ethnicity), socioeconomic (income and insurance type), geographic (area of residence), disease-specific (NHL subtype and stage), and facility-specific factors (type and location) showed that the facility volume was associated with OS. Compared with patients at Q4 facilities, patients at lower quartile facilities had higher mortality (hazard ratio for Q3, 1.05 [95% confidence interval, 1.04-1.06]; hazard ratio for Q2, 1.08 [95% confidence interval, 1.07-1.10]; hazard ratio for Q1, 1.14 [95% confidence interval, 1.11-1.17]).CONCLUSIONS:
NHL patients treated at higher volume facilities may survive longer than those treated at lower volume facilities. Further work is needed to understand the mechanisms of these differences and whether volume should be considered in the determination of referrals for NHL patients.
Non-Hodgkin lymphoma patients treated at higher volume facilities survive longer than those treated at lower volume facilities. This volume-outcome relation persists even after adjustments for case-mix differences.