A Population Based Patterns of Care Study for Male Breast Cancer in Ontario.

Abstract

Abstract Background: Tamoxifen has been the standard endocrine treatment for both early breast cancer (EBC) and metastatic breast cancer (MBC) in women for over 30 years(y). Over the last decade the third generation aromatase inhibitors (AIs) have proven effective in the treatment of MBC and are incorporated into adjuvant therapy for EBC. Due to the rarity of male breast cancer there are no trials to guide therapy and treatment decisions in men are made by extrapolation from the existing published data for women. We set out to conduct a population based cohort study in the most populous Canadian province to describe contemporary patterns of Tamoxifen and AI use for male breast cancer from 1992-2007.Methods: In the province of Ontario cancer reporting is mandatory and date of diagnosis (Dx) and death are collected by the Ontario Cancer Registry (OCR), but stage information is not uniformly available. The government of Ontario subsidizes drugs for individuals >65y through the Ontario Drug Benefits (ODB) program and maintains electronic prescription records for all eligible citizens. Linkage of these administrative databases allowed us to assemble a cohort of male breast cancer cases in order to describe patterns of endocrine therapy and outcomes.Results: Through OCR we identified 845 cases of invasive male breast cancer (ICD9 175) with a date of Dx between 03Jan1992 and 27Dec2007. Mean age at the time of Dx was 66.9 ±12.6y, median age was 68y, range 16-97y respectively. A total of 490 men were ≥66y at Dx. Using ODB prescription records between 01Jan1992 and 31Dec2008 we looked for a first prescription for any of the following drugs: Tamoxifen(T), Anastrozole(A), Letrozole(L), or Exemestane(E). As stage information is not uniformly available in OCR, prescription <12 months from Dx was used as a surrogate for therapy with adjuvant intent (EBC group) and those with a first prescription for T or an AI >12 months from Dx were classified as MBC. Using these criteria, 172 cases received no prescription for endocrine therapy (35.0% stage unknown), 297 cases were EBC (271 prescribed T (55.3%) and 26 prescribed an AI (5.3%) < 1 y of Dx and 21 (4.3%) were MBC being prescribed either T or an AI > 1 y post Dx. Prescription of endocrine therapy increased over time: 60% (92-99) vs. 68% in (00-08) At a median follow up of 46.3 months overall survival(OS) is 64.96% for the entire group, 53.27% for stage unknown, 72.17% for EBC and 60.53% for MBC and has not changed significantly over time; 66.33% for 92-99 and 64% for 00-08 for the group as a whole.Conclusions: In this provincial cohort of male breast cancer spanning a 15 y period we observed that: 1) most men are prescribed some form of adjuvant endocrine therapy and in keeping with the paucity of data for AIs in male breast cancer, Tamoxifen was the most commonly prescribed agent; 2) use of endocrine therapy increased over time; 3) overall survival has not changed significantly over time. This study is limited by its use of administrative data, retrospective nature, and by the surrogate assignation of stage. That said, it does represent the largest cohort of male breast cancer and describes trends in modern endocrine therapy. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2108.