Breast cancer specialists are welcoming information from two, recently-released studies that estimated risks for the disease from certain genetic variants and mutations.
“These studies provide welcome information outlining estimated risks of breast cancer in less well-studied genes,” said Baystate Health’s Dr. Grace Makari-Judson. “Many of these genes are considered as ‘low-to-moderate penetrance genes,’ meaning that most people that inherit these genes will still not develop cancer. This was substantiated when testing women with known breast cancer compared to those tested purely on family history.”
Makari-Judson, an oncologist, is associate medical director for cancer services, and medical director of the family cancer risk program in the Baystate Regional Cancer Program.
Of the limitations of the studies, published in the New England Journal of Medicine, Makari-Judson added, “The more information we have, the better we can counsel women, but more research is needed to obtain accurate estimates of lifetime risk of cancer and to understand how well risk-reducing strategies and increased surveillance work in these specific populations.”
Her comments were echoed by Dr. Nada Kawar of Mercy Medical’s Center for Breast Health and Gynecologic Oncology who called the studies overall “both very helpful, but not practice-changing.”
“The studies provide more numerical values to tell patients as I counsel them and the question of whether they decide to change their clinical management, change the kind of surgery they have or whether they decide to take medication to help decrease their risk, that will have to be a discussion,” said Kawar, who specializes in cancers of the breast and reproductive system as a gynecologic oncologist.
“It will not dramatically change our practice now because a lot of these genes have already been identified, but we will have more definitive numbers to quantified the risk.”
One of the studies looks to better inform genetic counseling on the overall risk ratio for breast cancer associated with certain genetic variants, as well as risk for type of breast cancer and what genes are most clinically useful for inclusion on a panel to predict risk.
Funded by the European Union Horizon 2020 programs among others and involving a large number of researchers, the study analyzed samples from 60,466 women with breast cancer and 53,461 women who did not as the control group. Its results included finding certain variants associated with a higher risk for estrogen-receptor positive breast cancer compared to ER-negative while others showed higher risk for ER-negative breast cancer.
The other study, funded by the National Institutes of Health and the Breast Cancer Research Foundation, looks to provide estimates of breast cancer risk linked to genetic alterations in known breast-cancer disposition genes, including the BRCA 1 and 2 genes, in the U.S. population, and to better inform screening and clinical management strategies for them.
This study involved 32,247 women with breast cancer and 32,544 who did not as the control group, and sequenced a custom multigene panel to identify germ line pathogenic variants in 28 cancer-predisposition genes. Pathogenic variants in 12 established breast cancer–predisposition genes were detected in 5.03% of the breast cancer cases and in 1.63% of those without breast cancer. Pathogenic variants in the genes known as BRCA1 and BRCA2 were associated with a high risk of breast cancer, with odds ratios shown in the study of 7.62, and 5.23 respectively.
“Over recent years, we have evolved from testing of BRCA1 and 2, to testing of smaller 8 to 10 gene panels to now testing which includes upwards of 27 to 77 genes,” Makari-Judson said.
“The more genes we test, the more likely it is that we identify a gene that we have limited information to quantitate lifetime breast cancer risk. The information on effective strategies to prevent or effectively screen for cancer in individuals with these genetic variants is even more limited.”
Asked about how the new information might help inform a woman’s treatment decision, she presented “an example of how this comes up in counseling a woman who has inherited a ‘moderate-risk’ gene that is associated with lifetime risk of 20-25%.”
“This is higher than the average women, whose risk is 13%, but much lower than the risks associated with BRCA1 that could be as high as 70 to 80%,” Makari-Judson said.
“Is it worth having a preventative mastectomy when the odds are that this woman would never have breast cancer? Other strategies include watching a woman more closely for example, with breast MRI and considering taking risk-reducing anti-estrogen medications such tamoxifen, raloxifene or an aromatase inhibitor. This approach makes more sense even though these strategies have not been specifically studied in many of these hereditary syndromes.”
Kawar noted as well that “a lot of these genes” in the NIH study have been previously identified and are tested for, but that the study gives “patients a little bit more odds ratio.”
“We have not been able to necessarily quantify the risks as much and this does give us more of a way to do that and give patients a little bit more odds ratio, their risk of getting cancer more than others,” Kawar said.
“This does help in a discussion of how to approach any further treatments, medication, surgeries.”
Kawar said there has been an explosion in genetic information in the last 10 years, helped in part by the fact the Supreme Court in 2013 said isolated human genes could not be patented.
“A lot of different companies were able to begin sequencing,” said Kawar, adding this allowed for better identification of genes and their function.
Kawar said genetic testing for cancer looks for “mutation in that original genetic code.”
Dr. Nada Kawar specializes in cancers of the breast, cervix, endometrium/uterus, fallopian tube, ovary, vagina and vulva as a gynecologic oncologist, and practices at what is now Mercy Medical's Center for Breast Health and Gynecologic Oncology, formerly its Breast Care Center.
“This is where they take blood samples from patients and what is tested is the genetic information you inherited to see if there are mutations in that original genetic code you got from your parents,” Kuwar said.
“This can be done from a cheek swab or a blood test, which we use at Mercy because it is easy and patients can just go to the lab here and get their blood drawn in a tube that comes in a kit provided by the company doing the testing and that is then mailed to them. The company runs the DNA in these panels where they are checking for mutations in multiple genes within the DNA of the sample collected. The most common breast genes would be checked.”
Kawar added, “The genetic testing company we used at Mercy is Ambry and they have a panel of 68 genes, some of which are affiliated with breast cancer, some of which are not but in order for us to learn about what cancers are associated with what genes it requires us to collect that data on patients that develop cancer.”
“Everyone has changes in their genes,” Kawar said.
“It is whether or not those changes cause a change in the function of the gene in the protein it produces and whether that then develops a problem that can lead to cancer developing.”
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