Some breast cancers need estrogen to grow. New treatments -- Arimidex, Aromasin, and Femara -- plus the old standard, tamoxifen, shut off the tumors' estrogen supply. Because of these treatments, women with estrogen-sensitive tumors (ER-positive tumors) are more likely to remain cancer-free than women with tumors not sensitive to estrogen (ER-negative tumors).
The good news doesn't stop there. Estrogen-blocking treatment is so effective, most women with ER-positive breast cancer will do fine without chemotherapy.
The findings come from a close analysis of data from three studies of women with breast cancer that had already spread to at least one lymph node. Donald A. Berry, PhD, of the University of Texas M.D. Anderson Cancer Center, Houston, and colleagues report the findings in the April 12 issue of The Journal of the American Medical Association.
"Our results indicate that advances in chemotherapy have lessened the survival differences between ER-positive patients who receive hormonal therapy and ER-negative patients," Berry and colleagues write. "[ER-negative] patients derive much greater benefit from modern improvements in chemotherapy regimens."
The researchers make two major points:
- The benefit of chemotherapy for patients with ER-positive breast cancer is "modest at best."
- Modern chemotherapy has vastly improved the prognosis for ER-negative patients.
Berry and colleagues note that estrogen sensitivity testing isn't perfect. Some women with ER-positive tumors do benefit from chemotherapy. But it isn't yet possible to tell which women need this aggressive treatment and which ones definitely don't.
"In the years ahead, it is likely that we will have better predictors that will allow clinicians to determine which patients with ER-positive disease truly benefit from the addition of chemotherapy," Berry and colleagues write.