CIHI says further analysis of clinical practices and patterns could provide answers
A new report released by the Canadian Institute for Health Information (CIHI) says the rate of mastectomies to treat breast cancer is higher in Newfoundland and Labrador than any other Canadian province.
The report, "Breast Cancer Surgery in Canada, 2007-08 to 2009-10," says the rate of mastectomies among women with unilateral breast cancer varies across the country from 26 per cent in Quebec to 69 per cent in Newfoundland and Labrador.
Among women with ductal carcinoma in situ (DCIS) — which is considered non-invasive breast cancer — the mastectomy rate is again the highest in Newfoundland and Labrador at 67 per cent. Quebec has the lowest rate of mastectomies in this group as well, at only 17 per cent.
The CIHI says breast-conserving surgery and radiation is generally recommended over mastectomy because it is less invasive and is associated with "fewer morbidities and equivalent survival as mastectomy."
The institute says the differences in mastectomy rates by province raise many questions and additional analyses of clinical practices and patterns could provide some answers.
In this regard, the CIHI says examining a wide variation in rates of re-operation and, in particular, the performance of mastectomy on women initially treated with less invasive breast-conserving surgery might be informative.
The CIHI also says a relatively high rate of mastectomy following initial breast-conserving surgery among women in certain jurisdictions appears to be contributing to high rates of mastectomies in these jurisdictions.
According to the CIHI, a woman’s choice of procedure is often based on "the extent of her disease and her personal preferences after considering the benefits and risks associated with each procedure."
It says "some women’s choices, however, may be influenced by non-clinical factors, such as access to care or practice patterns that are not evidence-based."
Other possible explanations noted by the CIHI for high rates of mastectomies in some provinces could include differences in severity of disease, the relative health of women undergoing surgery, clinicians’ surgical preferences and undocumented socio-economic factors.
The CIHI says some women who initially undergo breast-conserving surgery require subsequent operations to remove additional tissue (known as re-excision) if, for example, pathologic examination of the tissue initially removed does not show clear margins of cancer-free tissue surrounding the tumour.
The rate of re-excision within one year for women who had breast-conserving surgery as their index procedure also varies greatly by province, with Newfoundland and Labrador against having the highest rate at 56 per cent and Manitoba and Quebec, the lowest at 17 per cent. The CIHI says in many of these cases, women who initially underwent breast-conserving surgery had a mastectomy within a year.
The use of day surgery for breast-conserving surgery also varies across the country, from 41 per cent in Prince Edward Island to 86 per cent in Newfoundland and Labrador.
Eastern Health, the province’s largest health board, says its mastectomy rate among Stage 1 and Stage 2 breast cancer patients is lower than the provincial rate reflected in the report. In 2009 to 2010, the mastectomy rate among both groups of patients in the Eastern Health region was 56.5 per cent, according to a health authority spokeswoman.
There are four health boards in Newfoundland and Labrador.
The CIHI report concludes that female breast cancer takes a heavy toll in Canada.
In 2012, it's estimated that 22,700 women will be diagnosed with invasive breast cancer, and 5,100 women will die of the disease.
Fortunately, with population-based screening programs, the CIHI says most women today are diagnosed with early stage breast cancer and have a very good prognosis following treatment, which in most cases, involves surgery.
Each year, an estimated 22,000 Canadian women undergo surgery for breast cancer.
The institute says more in-depth studies using "supplementary data sources and designs with a longitudinal component" would contribute to an improved understanding of the provincial variations.