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study shows no significant difference in mortality rates among common breast cancer treatments
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three common cancer treatments all come with the same mortality rates, a new study shows.
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a study conducted by a team of researchers at women’s college hospital research and innovation institute has found that bilateral mastectomy for unilateral breast cancer may not be as beneficial as once thought, but only as it pertains to mortality rates.
the long-term study followed 108,084 patients living with breast cancer over 20 years to determine what form of treatment is best for reducing the risk of mortality caused by breast cancer.
the initial thought was that a bilateral mastectomy for unilateral breast cancer was a viable route to take to reduce the risk of mortality due to the fact that it reduces the chances of contralateral cancer development.
unilateral breast cancer occurs when only one breast is affected or has a tumour, and a bilateral mastectomy is a surgery to remove both breasts.
however, the results showed that the three surgical forms of treatment often used for breast cancer removal, unilateral mastectomy, bilateral mastectomy, and lumpectomy, were found to have almost identical rates of mortality across the board.
dr. vasily giannakeas, lead author of the study paper and medical researcher at the women’s college hospital research and innovation institute, and the team of researchers who conducted the study aimed to assess risk versus treatment in people with breast cancer.
“what we were really interested in determining was if there were any sort of clinical benefits based on three surgical options that women with breast cancer have,” he said. “specifically, we’re looking at the impact of these surgical options on reducing contralateral breast cancer risk and on reducing breast cancer mortality.”
unilateral breast cancer and the risk of recurrence and contralateral breast cancer
unilateral breast cancer is the most common way that breast cancer develops. however, once the cancer develops in one breast, the risk of it spreading or developing in the other is higher than in those who have never had breast cancer at all.
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according to statistics, roughly eight to 10 per cent of people who develop unilateral breast cancer will go on to be diagnosed with a second breast cancer after 25 years. the risk is slightly lower after seven years, at only three per cent.
when looking at contralateral breast cancer, the type that develops in the opposite breast, the risk is marginally lower. some studies suggest that it’s often a rare occurrence at roughly 2.4 per cent.
however, in the study conducted by dr. giannakeas and researchers, they found the risk of developing contralateral breast cancer without a bilateral mastectomy, or in those who had and treated breast cancer in the opposite breast, was roughly seven per cent, more than double of what data shows in other studies.
the risk of developing contralateral breast cancer was also found to be significantly lower, or close to non-existent, in those who had a bilateral mastectomy.
“if they did do a bilateral mastectomy, that risk would drop to less than one per cent,” said dr. giannakeas. “these findings are not surprising. if a woman removes both breasts, the risk of her getting a cancer in the opposite breast in the future will go down drastically…one of our goals of our study was to demonstrate with high accuracy what that risk is.”
unilateral breast cancer and risk of mortality based on treatment
according to the canadian cancer society, roughly one in every 36 people who develop breast cancer will succumb to the disease, regardless of their chosen treatment avenue. in the study, the researchers aimed to determine the mortality rate based on three specific treatments, as mentioned above.
after the data had been accumulated after the 20-year period, it was found that the risk of mortality was nearly identical for all forms of treatment. those who underwent a lumpectomy had a mortality rate of 16.3 per cent, and those who opted for unilateral or bilateral mastectomies were found to have the exact same mortality rate at 16.7 per cent.
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essentially, going the bilateral mastectomy route does reduce the risk of developing new cancer, but it does not affect whether or not a person will die from breast cancer once it develops.
“what we’re really trying to wrap our head around from a breast cancer theory perspective is we have all these women that are developing a second cancer, and if they get that second cancer, their risk of death goes up so much and yet preventing that second cancer through surgical means does not impact on mortality,” dr. giannakeas said. “that’s one of the big questions that we’re really trying to answer.”
next steps and future directions
currently, the three treatment options given to patients allow them to choose what is most comfortable for them and their personal journey with breast cancer. none of the therapies are pushed more than others by clinicians who work with breast cancer patients.
but there is a sense of fear surrounding developing a second cancer. if that second cancer does develop, the fear of it increasing the risk of mortality may sway people into choosing a bilateral mastectomy when this new data suggests there is no variability in mortality rates regardless of whether the second breast was removed along with the first, cancerous one.
“patients are confronted with the fear of developing a cancer in the opposite breast, and in the future, and also undergoing routine mammography screening either every six months or every year after their first cancer to look for the presence of a second cancer in the opposite breast,” dr. giannakeas said.
“if they do develop a cancer in the opposite breast, they’ll have to then undergo some additional treatment, such as surgery, possibly radiotherapy or chemotherapy, so they have all these things to think about that could potentially happen down the line. they (those that choose bilateral mastectomy) ultimately decide they want to avoid all these potential scenarios by just removing their opposite breast.”
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this new data can help provide breast cancer patients with more to think about when it comes to their options, especially if mortality is their biggest fear. on the theoretical side, dr. giannakeas finds that there’s a disconnect between the data and what’s already been accepted as valid in terms of treatments versus mortality risk.
“where we need to go forward with research is trying to understand what’s going on in terms of the natural history of breast cancer and what’s actually causing this observation where you’re preventing cancers, but you’re not necessarily reducing mortality,” he said. “our current hypothesis is that the contralateral breast cancer, which has been thought to be an independent new cancer, we think may actually be some sort of marker for the presence of metastases.”
this new evidence suggests that there may be more to contralateral breast cancer than once thought, and its development could act as a sign that “there’s an increased risk of spread of cancer somewhere else in the body.”
“i hope that our research contributes to the body of evidence which suggests that many of these surgical options are safe and equally as effective at preventing death from breast cancer,” said dr. giannakeas. “ultimately, the patient should have the choice to decide which treatment they would like and given accurate estimates for the risk of contralateral breast cancer in the future as well as the risk of dying from breast cancer.”
as research forges on, more questions will need to be answered to paint a clearer picture of how the different treatments and types of breast cancer all have the same mortality rate, regardless of the route it took to get there. once that happens, clinical practices can utilize the results in a meaningful way to help patients living with breast cancer.
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“we need to do more research to figure out whether it’s necessary to do additional treatments, such as chemotherapy or screening for that second cancer, because we might be able to deescalate treatment and improve patients’ lives without necessarily impacting on their mortality,” dr. giannakeas said.
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