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.

Acknowledgements

The study was financially supported by The Norwegian Cancer Society. We want to thank Einar Hannisdal, Eva Skovlund and the Clinical Research Unit at the Norwegian Radium Hospital, Oslo University Hospital for important help in randomization, data handling, and statistical analysis; Gry Skare at the Cancer Registry of Norway for estimating the amount of patients available for randomization in these trials; and all the physicians enrolling patients into this study.

The following hospitals (in alphabetical order in Norwegian) included patients in the three studies: Aker sh, Aust-Agder Ssh, Bærum sh, Buskerud Ssh, DNR, Diakonhjemmets sh, Diakonissehjemmets sh, Farsund sh, Fsh Florø, Flekkefjord sh, Fsh i Lærdal, Fsh i Molde, Fsh på Stord, Fsh på Voss, Fsh i Kristiansund, Fsh i Volda, Gjøvik Fsh, Hammerfest sh, Hamar sh, Halden sh, Harstad sh, Haugesund Fsh, Haukeland sh, Betanien sh, Indre Østfold sh, Innherred sh, Kirkenes sh, Kongsberg sh, Kongsvinger sh, Larvik sh, Lovisenberg sh, Lillehammer Fsh, Moss sh, Namdal sh, Nordland Ssh, Orkdal sh, Rana sh, RiTø, RiT, Ringerike sh, Sandnessjøen sh, Ssh i Møre og Romsdal, Ssh i Rogaland, Ssh i Sogn og Fjordane, Telemark Ssh, Ssh i Akershus, Stokmarknes sh, Tynset sh, Ullevål sh, Vest-Agder Ssh, Vestfold Ssh, Østfold Ssh.

No sponsors have influenced data interpretation or manuscript production. The corresponding author and two co-authors (ABJ and SL) had full access to all data. The corresponding author had final responsibility to submit the manuscript.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.