Obese and overweight women are more likely to experience breast cancer recurrence compared to women of normal weight, regardless of the type of cancer treatment they received, researchers reported in the journal Cancer. Joseph Sparano, MD, of the Albert Einstein College of Medicine’s Montefiore Medical Center, New York, and team explained that the patient does not necessarily have to be obese, she may be just within what is considered as overweight. He added that the higher recurrence risk is for the most common type of cancer.
The authors believe that excess body fat may trigger hormonal changes and inflammation that encourage the spread and recurrence of cancer, despite the type of treatment that was administered.
Dr. Sparano and team, consisting of oncologists from all over the USA, gathered data on the health outcomes of overweight and obese patients with stage I-III breast cancer; all the women had taken part in three trials – E1199, E5188, and E3189 – led by the Eastern Cooperative Oncology Group, which is now part of the ECOG-ACRIN Cancer Research Group.
In the three human studies, all the patients had normal bone marrow, liver, kidney and heart function, thus excluding variables which might impact on the results. Their aim was to focus on the impact of obesity and some other factors on cancer survival and recurrence.
They found that women with higher BMIs (body mass indexes) had significantly higher mortality and breast cancer recurrence rates compared to those whose BMIs were between 20 and 25. These risks persisted even among women who received ideal treatment for their breast cancer, including hormonal therapy and chemotherapy.
BMI (body mass index) is a statistical measurement which is derived from the person’s height and weight. A BMI below 20 is considered as underweight, between 25 and 29.9 is overweight. Any BMI measurement of at least 30 means the person is obese. BMI is a useful way of determining somebody’s ideal weight status if that person is not an athlete; athletes tend to have much more muscle, which weighs more than fat, so they will have a higher BMI without being overweight (without having too much fat).
The association between overweight/obesity and higher recurrence and mortality was especially noticeable among those with hormone receptor-positive breast cancer; this type accounts for over 60% of all breast cancers.
Dr. Sparano said:
“We found that obesity at diagnosis of breast cancer is associated with about a 30 percent higher risk of recurrence and a nearly 50 percent higher risk of death despite optimal treatment. Treatment strategies aimed at interfering with hormonal changes and inflammation caused by obesity may help reduce the risk of recurrence.”
When the doctor receives the patient’s pathology report, it will include the results of tests that tell whether the breast cancer cells have receptors for estrogen or progesterone – hormone receptors. These receptors are proteins, they also exist on breast cells, they respond to hormone signals that instruct the cells to grow.
- ER+ – if a cancer has estrogen receptors, it is called ER+ (estrogen-receptor-positive). This means the cancer cell receptors receive signals from the hormone estrogen that encourage their growth.
- PR+ – if the cancer cells have progesterone receptors, they are called PR+ (progesterone-receptor-positive). They receive progesterone signals from the hormone progesterone telling them to grow.
ER+ and PR+ are examples of hormone receptor-positive breast cancers.
Doctors need to know whether a breast cancer is a hormone receptor-positive one, because it will decide what treatment plan the patient needs to follow. Most breast cancers that have hormone receptors respond to hormonal therapy and some other treatments, while hormone-receptor-negative breast cancers do not. A hormone-receptor-negative cancer means there are no receptors for the signals from hormones – the cancer will not respond to instructions to grow from hormones.
Written by Christian Nordqvist