This study published on March 6 in Cancer Epidemiology, Biomarkers and Prevention reported that women who had a breast cancer recurrence had almost twice as much estrogen in their blood than women who remained cancer-free after treatment.
There is a hopeful message here. Although it seems logical that higher blood levels of estrogen might be responsible for breast cancer recurrence, until now surprisingly few studies looked at the estrogen levels of breast cancer survivors. Dr. Jennifer Wu of the Lenox Hill Hospital in New York City, explains:
That's the reason we use drugs that help lower estrogen levels. Estrogen causes increased cell division; we think it can perhaps start breast cancer. But this is a good study in that it has a lot of patients and proves that they have a demonstrable increase in estrogen levels over patients who don't have a recurrence.
In this study of 306 women breast cancer survivors, 2/3 were using tamoxifen, a drug that interferes with estrogen's effect on the body.
But, as study author, Cheryl Rock, a professor of Family and Preventive Medicine at the University of California, San Diego School of Medicine, says:
Anti-estrogen drugs can only have so much impact. There are two things apart from these drugs that can help to lower estrogen, or we believe it can, because it can in the general population. One is moderate to vigorous exercise, and the other is healthy weight management, achieving an ideal weight.
At issue here is the often under-reported fact that estrogen isn't only produced by the ovaries, but it's also produced by our fat tissue. The more fat tissue, the more circulating estrogen in the body. The more estrogen circulating through the body, the more likely a recurrence.
So how exactly can exercise and diet lower the body's estrogen levels? We all have a protein in our bodies, called sex hormone-binding globulin, which binds the circulating estrogen to itself, and in effect keeps the estrogen from entering cells, like breast tissue. As long as the estrogen is attached to the SHBG, you're in good shape, as Dr. Rock explains:
- If you are overweight you have higher insulin levels in your blood
- Higher insulin levels decrease the production of SHBG, and estrogen doesn't have a place to "bind" to. It's free to enter our tissues.
- Exercise not only keeps your weight down, but it decreases insulin production = more SHBG production = less free-floating estrogen
- Better diet with more fiber & less refined sugar and flour = lower insulin levels = more SHBG production = less free-floating estrogen
The final piece of good news with this study is the validation that in spite of drugs like tamoxifen different women have different estrogen levels and it is important to monitor them after initial treatment. Higher levels can put you at risk for a recurrence. As Dr. Wu explains:
This study justifies the use of drugs that help decrease estrogen levels like tamoxifen and aromatase inhibitors. [In the future], we may want to titrate different levels of anti-estrogen medications. Right now, we have a standard dosage for everyone, whereas women who are heavier or other women who may have higher estrogen levels for one reason or another may need larger doses.