The Incidence, Management, and Outcome of Inflammatory Breast Cancer

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Fralick, John
inflammatory breast cancer , incidence , survival , trends , management
Background: Inflammatory breast cancer (IBC) is a rare form of breast cancer associated with a poor prognosis. This study describes the incidence, survival, and management of IBC in the province of Ontario. Methods: We conducted a retrospective, population-based, cohort study using data systems held at the Division of Cancer Care and Epidemiology at Queen’s University in Kingston, Ontario. Using the Ontario Cancer Registry (OCR), we identified all primary, pathologically confirmed cases of breast cancer. IBC cases were identified using the unique histology code ‘85303’. OCR records were linked to Statistics Canada data, Canadian Institutes of Health Information (CIHI) records of surgical procedures, and cancer centre records detailing radiotherapy and chemotherapy administration. We calculated age-adjusted incidence rates of IBC for cases diagnosed between 1984 and 2005. Using the Kaplan Meier product-limit method and log-rank statistics we compared overall survival for IBC and non-IBC, and assessed temporal and regional variations in IBC survival. We described the management of IBC for patients diagnosed between 1984 and 2004, and assessed variations over time and across cancer centres. Results: Age-adjusted incidence rates of IBC increased from 0.57/105 women-years in 1984-1987 to 1.15/105 women-years in 2003-2005 (p<0.0001). 10-year survival was 21.5% for IBC compared to 61.7% for non-IBC (p<0.0001). For IBC, 10-year survival increased from 12.0% (95% CI: 8.3–16.3) for those diagnosed between 1984-1994 to 24.0% (95% CI: 20.1–28.2) for those diagnosed between 1995-2005. The utilization of combined mastectomy and postoperative radiotherapy increased from 28.9% in 1984-1994 to 46.1% in 1995-2004 (p<0.0001). We observed no statistically significant difference in the utilization of chemotherapy over time. Differences in the utilization of combined mastectomy and postoperative radiotherapy were observed across cancer centres (29.8% at centre C vs. 54.7% at centre A, p<0.0001). We also observed wide variations in the estimates of survival across cancer centres. Discussion: Rates of IBC have increased over time in Ontario and we observed an improvement in the long-term survival. Management has shifted over time towards increased use of mastectomy and postoperative radiotherapy. Additional prognostic information is needed to determine how variations in practice may be related to variations in outcome.
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