When estrogen-lowering drugs no longer control metastatic breast cancer, the opposite strategy might work. Raising estrogen levels benefited 30 percent of women whose metastatic breast cancer no longer responded to standard anti-estrogen treatment, according to research conducted at Washington University School of Medicine in St. Louis and collaborating institutions.
The results are reported in the Aug. 19, 2009, issue of the Journal of the American Medical Association. Not only did estrogen treatment often stop disease progression, in some patients metastatic tumors became resensitized and again responded to anti-estrogen treatments.
"The women in the study had all experienced a relapse while on estrogen-lowering drugs, and their disease was progressing," says lead author Matthew J. Ellis, M.D., Ph.D., an oncologist with the Siteman Cancer Center at Washington University and Barnes-Jewish Hospital. "So they were faced with undergoing chemotherapy. We found that estrogen treatment stopped disease progression in many patients and was much better tolerated than chemotherapy would have been."
About 40,000 women die of metastatic breast cancer each year, and estrogen therapy could potentially help thousands of women, Ellis says. Furthermore, he points out that the therapy is inexpensive, costing less than a dollar a day.
Sixty-six postmenopausal women with breast cancer that had spread beyond the breast participated in the study. All participants were originally diagnosed with estrogen receptor positive (ER ) breast tumors, meaning estrogen stimulated tumor growth. Seventy-five percent of breast cancer cases are ER . All participants had received aromatase inhibitor treatment, which severely lowers estrogen levels, but their metastatic tumors had later reappeared or resumed growing.
The study compared a high 30-milligram daily dose of estrogen to a low 6-milligram daily dose, and evaluated how well the treatments controlled the women's metastatic cancers and how the treatments affected their quality of life. The high dose results in estrogen levels in the blood comparable to that of pregnant women, while the low dose gives estrogen levels similar to that of women who are ovulating, Ellis indicates.