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 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."