The mastectomy data include women who receive a mastectomy first (labeled Index) as well as women who receive breast conserving surgery first followed by a mastectomy within one year (labeled Final).
Data source: Canadian Institute for Health Information, Hospital Morbidity Database, National Ambulatory Care Reporting System; Alberta Health and Wellness, Alberta Ambulatory Care Reporting System.
The mastectomy data include women who receive a mastectomy first (labeled Index) as well as women who receive breast conserving surgery first followed by a mastectomy within one year (labeled Final).
Data source: Canadian Institute for Health Information, Hospital Morbidity Database, National Ambulatory Care Reporting System; Alberta Health and Wellness, Alberta Ambulatory Care Reporting System.
This indicator measures the percentage of women who underwent mastectomy among those who had breast cancer surgery to treat unilateral invasive breast cancer. We are presenting the percentage of patients who received mastectomy as their first surgery (i.e., index) and the percentage of patients who underwent mastectomy first or mastectomy within a year of having breast-conserving surgery (i.e., final). Results are presented by province and include breast cancer resections that occurred between April 2008 and March 2013.
Most women diagnosed with non-metastatic breast cancer are candidates for surgery—either mastectomy or breast-conserving surgeryc typically followed by radiation therapy, referred to as breast conserving therapy (BCT).108 BCT is less invasive than mastectomy and is associated with lower morbidity, improved cosmetic appearance and better psychological outcomes. Evidence shows that mortality from non-metastatic breast cancer is equal across both procedures.
What are the results?
The use of index mastectomy (where mastectomy was the first choice procedure) ranged from 20.9% in Quebec to 56.4% in Saskatchewan (Figure 4.23). The final mastectomy rate ranged from 25.3% in Quebec to 68.3% in Newfoundland and Labrador (Figure 4.23). This suggests substantial variation in breast cancer surgical practice among provinces. Note that the difference between the index and final rates within a province may reflect the proportion of mastectomies that followed unsuccessful breast-conserving surgeryd.
What do the results mean?
Because mastectomy and breast-conserving therapy (BCT) yield comparable survival outcomes, the interprovincial differences shown here do not necessarily reflect differences in the appropriateness of treatment or the quality of care. While BCT should be considered for most early-stage breast cancer patients, there are no formal Canadian performance targets for the actual treatment rate. The choice of BCT versus mastectomy should be made by the breast cancer patient based on a clear understanding of the risks, benefits and practical considerations associated with each choice.
There is evidence that the proportion of patients with limited access to radiation therapy (e.g., those who live far away from a treatment centre) does influence BCT rates.109-113 Patients who live far from the nearest radiation treatment centre may be less likely to have BCT than mastectomy due to the challenges of travelling to a treatment facility regularly for five to seven weeks of treatment. Newfoundland and Labrador, which had the highest final mastectomy rate, has just one radiation centre to serve the entire province. Saskatchewan, which had the highest index mastectomy rate, has two radiation centres that are located in the main metropolitan areas (Saskatoon and Regina). Ontario and Quebec, which had among the lowest mastectomy rates, also have the most radiation treatment centres. While some are located in the northern parts of the provinces, many women still live long distances away from the centres. Data on the percentage of the Canadian population living within a short distance to a radiation centre are not available.
Some interprovincial differences in rates of mastectomy may be explained by the use of diagnostic excisional biopsies across provinces. In recent years, the use of core needle biopsy (where a hollow needle is used to excise a sample from the suspect tissue) has been recommended over excisional biopsy (a surgical procedure in which the suspect breast tissue is removed) as the diagnostic procedure of choice; however, the surgical option, while less common, is still used. Current coding practices in hospitals do not reliably distinguish between excisional biopsies and breast-conserving surgery. For this reason, provinces with higher excisional biopsy rates compared to other provinces may show a lower proportion of index mastectomies.114 Similarly, these provinces may have a higher proportion of patients undergoing initial breast-conserving surgery but who end up having a final mastectomy.
c Mastectomy is surgery to remove the entire breast; breast-conserving surgery involves complete removal of the tumour along with a margin of non-cancerous breast tissue.
d This occurs when the pathology report following breast-conserving surgery shows positive margins (i.e., cancer cells near the excised tissue).
The Partnership and the Canadian Institute for Health Information (CIHI) have collaborated on the analysis and reporting of breast cancer surgery patterns. A joint report published in 2012 presented data on breast surgery patterns and also highlighted variation by factors such as patient age, income and travel time to the nearest radiation centre.115 Further analyses at the local level may help identify opportunities for potential system improvements. For example, in Saskatchewan, a mastectomy working group has been established to further investigate the reasons for variations in that province and the factors that influence a patient’s choice to have mastectomy versus breast-conserving surgery.116
What else do we know?
The use of mastectomy can be influenced by many factors besides those already discussed here. These include: access to immediate breast reconstruction following mastectomy; prevalence of and testing for gene mutations that may predispose a woman to developing breast cancer (e.g., BRCA 1/2), which can influence the choice to opt for prophylactic (preventive) removal of one or both breasts; surgeon preference; clinical factors;e and personal preference.117
e Not every patient with invasive breast cancer is a good candidate for breast-conserving surgery. Women with certain types of tumours or who have contraindications to radiation therapy may choose to undergo mastectomy.114
Data for this indicator are based on hospital abstract databases maintained by the Canadian Institute for Health Information (CIHI) or data provided to CIHI. There was no linkage with data in provincial cancer registries. Thus data may include women with recurrent disease—although attempts to minimize this were made through the case selection criteria.
The data include women with unilateral invasive breast cancer whose surgery occurred between April 2008 and March 2013.
The procedure codes used do not differentiate between excisional biopsies and breast-conserving surgery. For this reason, patients who received excisional biopsy followed by mastectomy would have been grouped in the results with patients who received BCS first followed by mastectomy. Additionally, provinces with higher excisional biopsy rates compared to others may show a lower proportion of index mastectomies.
Definition: The percentage of surgical resections among women with unilateral invasive breast cancer that are mastectomies.
Numerator: Women in the denominator who received a mastectomy first as well as women who received breast conserving surgery (BCS) first followed by a mastectomy within one year
Denominator: Women with unilateral invasive breast cancer who received breast conserving surgery and/or a mastectomy
Data source: Hospital Morbidity Database, Canadian Institute for Health Information (CIHI); National Ambulatory Care Reporting System, CIHI; Fichier des hospitalisations MED-ÉCHO, ministère de la Santé et des Services sociaux du Québec; Alberta Ambulatory Care Reporting System, Alberta Health and Wellness
Measurement timeframe: 2007-08 to 2011-12
Stratification variables: Province/territory
Provinces submitting data: BC, AB, SK, MB, ON, QC, NB, NS, PE, NL and Territories
General notes: 1. The following surgical and diagnostic codes, as documented in hospital patient records and reported to CIHI, were used to identify diagnoses and procedures per the following:
In order to identify a breast cancer diagnosis, the following ICD-10-CA codes were used: 00, C50.01, C50.09, C50.10, C50.11, C50.19, C50.20, C50.21, C50.29, C50.30, C50.31, C50.39, C50.40, C50.41, C50.49, C50.50, C50.51, C50.59, C50.60, C50.61, C50.69, C50.80, C50.81, C50.89, C50.90, C50.91, C50.99. Women with unilateral invasive breast cancer were the focus of this analysis (comprising 98% of women with invasive breast cancer).
In order to identify a mastectomy, the following surgical codes were used according to CCI: 1.YM.89 to 1.YM.92.
The following CCI codes were used to identify a breast conserving surgery: 1.YM.87, 1.YM.88.
