Exercise May Protect Against Breast Cancer
Epidemiological evidence suggests that exercise reduces breast cancer rates and rates of breast cancer recurrence. However, it is not well understood why this is true.
Exercise that is intense enough to increase the heartrate and induce heavy breathing can increase the hormone epinephrine in the blood. A 2017 article by researcher Christine Dethlefson and colleagues in the journal Cancer Research reported that this elevated level of epinephrine in the blood of breast cancer patients after one intense exercise session stopped their breast cancer cells from growing in vitro and reduced tumor growth by half.
Senior author Pernille Hojman told Reuters that while exercise could not be expected to replace anti-cancer treatments, it is a great supportive strategy that has the added benefits of increasing patients’ quality of life and sense of empowerment.
The study looked at human breast cancer tumor cells in test tubes, and the same type of tumor cells implanted into mice. Only 45 percent of the mice implanted with the cancer cells collected after vigorous exercise developed tumors, compared to 90 percent of the mice who received cancer cells collected before exercise or with no exercise.
Hormone Replacement With Estrogen/Progestogen Combo Increases Breast Cancer Risk More Than Once Thought
A 2016 article in the British Journal of Cancer suggests that previous studies underestimated breast cancer risk in women who received hormone replacement therapy with the combination of estrogen and progestogen. The article by researcher Michael E. Jones and colleagues reported that combined hormone replacement therapy could increase the risk of breast cancer by more than three times, depending on how long a woman is exposed to the therapy. The longer the duration of use, the greater the risk of breast cancer. In the study, women who used other types of hormone replacement therapy, such as estrogen only or tibolone, did not have drastically higher rates of breast cancer than had been reported before.
Jones and colleagues suggest that previous studies did not use long enough follow-up periods to track whether women developed breast cancer while using hormone replacement. Their own study is based on a United Kingdom dataset known as the Breakthrough Generations Study. Study participants completed questionnaires at 2.5 years after recruitment, again at around 6 years, and again around 9.5 years. At the time of recruitment, women using combination hormone replacement therapy had been doing so for a median of 5.5 years.
Women who used combination hormone replacement therapy for 5.4 years were 2.74 times likelier to have breast cancer than those who didn’t receive hormone replacement. Using the combined therapy for more than 15 years increased risk 3.27 times compared to non-users.
The study also reported that as body mass index increased, breast cancer risk increased, regardless of hormone use.
While the study by Jones and colleagues was large (39,183 participants), the number of women who took combined hormone replacement and developed breast cancer was still fairly small (52). Seven of the 52 had taken the combined pill for more than 15 years. One limitation of this study is that these seven women may have skewed the risk assessments somewhat.
Experts suggest that women balance the possible risks and benefits of hormone replacement therapy. The therapy can be helpful in reducing symptoms of menopause, particularly hot flashes.
Using the lowest effective dose for the shortest time possible may be the best option. The increased risk of breast cancer drops after a woman stops using hormone replacement.
