The month of October every year is dedicated to creating awareness about breast cancer and rightly so!
This year, more than ever, there is a need to focus on breast cancer.
According to WHO: “The majority of deaths (269,000) occur in low- and middle-income countries, where most women with breast cancer are diagnosed in late stages due mainly to lack of awareness on early detection and barriers to health services. If no action is taken, and with the COVID-19 pandemic still creating chaos around the globe, there is no saying what the impact of COVID-19 may be on breast cancer patients.”
After getting treated for breast cancer, many survivors are left with a higher risk of developing diseases that affect the heart or blood vessels (cardiovascular disease).
Now, new research has found that having a cardiovascular event, like a heart attack or stroke, may in turn make breast cancer grow faster.
Much research is documented on the increased risk of cardiovascular events after breast cancer treatment, but the reverse is also being explored: “If breast cancer survivors have a cardiovascular event, does it impact their cancer?” investigated by Dr Kathryn Moore, PhD, of New York University’s Grossman School of Medicine.
The answer, Dr Moore and her colleagues found, is resoundingly yes. In their analysis, breast cancer survivors who had a cardiovascular event were more likely to have their cancer come back. They were also more likely to die from breast cancer.
new way of thinking
This study presents a “new way of thinking about how cancer and cardiovascular health may interact,” said Susan Dent, MD, an oncologist who wasn’t involved in the study.
Dr Dent is co-director of Duke University’s cardio-oncology programme, which focuses on the intersection of heart disease and cancer.
In studies of mice, the researchers found that a heart attack leads to changes in the immune system that permit cancer to grow and spread more easily.
The findings were published in July 2020 in Nature Medicine.
Although the findings are alarming, there are things breast cancer survivors can do to lower their risk of cardiovascular disease, Dr Moore emphasised.
That includes exercising, eating a healthy diet, and controlling their cholesterol and blood pressure, she said.
These strategies may not only reduce the risk of cardiovascular disease but also improve cancer outcomes, the researchers wrote.
Cardiac events spur
To see how cardiovascular disease impacts cancer, the scientists first analysed data from two older studies of women with breast cancer.
The studies tracked more than 1,700 women for an average of 12 years, during which time some developed cardiovascular disease.
The team focused their analysis on those women who didn’t have cardiovascular disease at the time that they were diagnosed with breast cancer.
Survivors who developed specific cardiovascular diseases and events—namely heart attack, stroke, heart failure, coronary artery disease, or arrhythmia—had a 59% higher risk of breast cancer coming back (recurring), the researchers found.
These women also had a 60% higher risk of dying from breast cancer than women who did not develop cardiovascular disease.
The researchers also studied mice with breast cancer. In some mice, they performed a surgical procedure to cause a heart attack. In another group of mice, they did the surgery without causing a heart attack (a “sham” surgery).
Breast cancer grew and spread faster in mice that had a heart attack.
Seventeen days after surgery, breast tumours in these mice were twice as big as those in mice that had the sham surgery.
Mice that experienced a heart attack also had twice as much breast cancer that had spread (metastasised) to the lungs.
The scientists observed these effects in mice that were engineered to develop breast cancer as well as in mice that were implanted with mouse breast cancer cells.
Immune cells change after heart attack
Dr Moore’s team’s usual focus is on clogged arteries (also called atherosclerosis), which can lead to a heart attack, stroke, and heart disease. In particular, they study why the immune system goes into overdrive when arteries are clogged.
The immune system’s exaggerated response to clogged arteries can make the clogs even worse.
Likewise, the immune response to cancer can sometimes make the cancer grow and spread more easily.
Because of the immune system’s role in both atherosclerosis and cancer, the researchers suspected that changes in the immune system might explain why cancer grows faster after a heart attack.
For instance, tumours of mice that had a heart attack contained fewer cancer-fighting immune cells and more “suppressor” immune cells—those that prevent the immune system from attacking cancer.
By toning down the immune response against cancer, suppressor immune cells can help tumours grow.
pay attention to
Many women who are diagnosed with breast cancer also have other diseases that raise the risk of cardiovascular disease, namely diabetes, obesity, and high blood pressure.
Those cardiovascular risk factors are not always under control when women start cancer treatment, Dr Dent explained.
“Then we give them cancer therapy, which may add to that risk.
“They finish their cancer therapy, and then they are sent back to their primary care doctor with little attention to their cardiovascular risks,” she said.
This study highlights the need for both breast cancer survivors and their doctors to pay more attention
to cardiovascular health.