Hospital volume and prognosis among Norwegian breast cancer patients enrolled in adjuvant trials

Abstract

Background. Several studies have reported an association between breast cancer unit volume and prognosis. We hypothesize that this may be due to inappropriate coping with the recommended guidelines for adjuvant therapy rather than improper breast cancer surgery provided at smaller units. Methods. A cohort of 1131 patients with operable breast cancer (pT_1-2 and positive axillary lymph nodes, stage II) enrolled between 1984 and 1994 were analyzed. The women had participated in one of three prospective trials on adjuvant endocrine treatment and were enrolled from 50 centers in Norway. The hospitals were categorized into four groups according to the annual number of surgically treated breast cancer patients reported to the national discharge database in 1990. The hospitals were also stratified according to whether they are university or non-university hospitals. To assess the effect of unit size on patient outcome, local recurrence rates and overall survival were compared in women treated at units with different patient volumes. Results. The median time from study enrolment to the end of the study was 10.5 years. Relapse-free survival and overall survival did not differ significantly between the hospital groups based on the surgical workload or between university and non-university hospitals. Conclusions. Patient volume or teaching status of a hospital did not have any impact on the prognosis of pre- or postmenopausal stage II breast cancer patients included in the adjuvant endocrine trials. Our data support the hypothesis that differences in survival related to patient volume at the treatment units may be explained by inappropriate adjuvant systemic treatment.