Breast Cancer Prevention Measures Vary Greatly

Allison Gandey

August 17, 2007 — Genetic testing is identifying women with BRCA1 or BRCA2 mutations, but preventive options can differ so dramatically, researchers are concerned. "The benefit of genetic testing is that we can identify women at high risk of developing breast cancer and hopefully reduce that risk. Ultimately, though, women have to elect to undertake 1 of the options," lead author Prof. Kelly Metcalfe, assistant professor at the Lawrence S Bloomberg Faculty of Nursing at the University of Toronto, in Ontario, told reporters. In an article published online August 17 in Open Medicine, the group shows that many Canadian women are not taking advantage of the preventive options available.
"Our results, and those of others, suggest that there are wide variations in the uptake of preventive options among BRCA1 and BRCA2 mutation carriers," the researchers write. "The differences in uptake could be due to a number of factors, including healthcare professionals’ acceptance and recommendation of the procedures, cultural differences that influence patient preferences, and access including cost and availability."
The team observed significant differences in uptake of preventive options in women who have received genetic testing in different areas of the country. The differences cannot be explained by differing healthcare systems, because Canada has a universal system, they suggest, and all of the women in the study had similar access to healthcare.
"We were very surprised by the discrepancy in preventive measures taken across the country," Prof. Metcalfe said. "The numbers show a huge discrepancy, with women in Quebec being the least likely to elect a preventive option. This will have significant implications in terms of the numbers of cancers we see developing in this high-risk group."
In the study, 672 women were identified as carrying the genetic mutation. Follow-up questionnaires were issued after a mean of 4 years. Out of the 342 women without breast cancer, 46% had not undertaken any cancer prevention option such as mastectomy, oophorectomy, or taking tamoxifen or raloxifene. Broken down geographically, 39% of women with the genetic mutation in Ontario, 34% in Western Canada, and 62% in Quebec did not take preventive measures.
The investigators suggest that prophylactic mastectomy offers the greatest reduction in breast cancer risk (approximately 95%). And prophylactic oophorectomy performed before the age of 40 years in women with a BRCA1 or BRCA2 mutation is associated with a 50% reduction in the risk for breast cancer. They report that using tamoxifen may also reduce breast cancer by 50% in high-risk women.
"Some women prefer screening over preventive surgery or chemoprevention," they add. "The goal is to detect cancer at an early, treatable stage."
The greatest differences in uptake rates were found with prophylactic mastectomy. Women from Western Canada had the highest rate of mastectomy (46%), followed by women from Ontario (22%), and Quebec (8%). The investigators also observed pronounced differences in rates of uptake of prophylactic oophorectomy. A total of 67% of women from Western Canada and 61% of women from Ontario had undergone preventive oophorectomy. Again, fewer women from Quebec elected to have this preventive surgery, with a total of just 39%.
The differences in tamoxifen uptake may also be due to access issues. Currently, tamoxifen costs approximately $25 per month. Some women may not have drug coverage and therefore may not be able to afford this.
"The differences in surgical uptake that we observed are probably not due to differences in access across the country. Canadian women have coverage for prophylactic surgeries, including breast reconstruction, without cost," the researchers write. "This would not be the case in the United States, where differences in uptake of preventive procedures have been attributed to financial constraints." But overall, the uptake rates of various preventive modalities were similar to those reported in other countries.
Large Sample, But May Not Be Representative
Data on uptake of magnetic resonance imaging were available for 241 of the 270 women without breast cancer who had not had a prophylactic bilateral mastectomy. A total of 104 (43%) had been screened for breast cancer with MRI. Most of these women — 96% — were less than 60 years old.
In contrast, the majority of women without breast cancer had undergone mammography (96%). Most of these women (86%) began mammography screening before genetic testing; however, 14% of the women had had their first mammogram after receiving their genetic test result.
"Although ours is a relatively large sample, it may not be representative of all women who have received a positive genetic test result in Canada," the investigators note. "Canadian women may have undergone genetic testing in centers other than the ones included here, and we do not have any information on their uptake of cancer prevention options."
They add that patterns of practice have evolved since 1999, the average time at which study subjects received genetic testing. "We believe that genetic services are now better integrated with surgical care and that physician attitudes may have changed with regard to specific preventive measures. It is our intention to repeat this survey in 5 years to evaluate trends in clinical practice."
This study could not ascertain the specific reason for the discrepancies across Canada, but the investigators say future research will address this question.
The researchers report having no significant financial relationships.
Open Medicine. 2007;1:e92-e98.