Study: Lower Doses of Tamoxifen May Be as Effective

Significantly lower doses of the drug tamoxifen may be just as effective as the standard dose in fighting breast cancer and have fewer side effects, according to Italian researchers reporting in the Journal of the National Cancer Institute.

But a number of other researchers quickly cautioned that more studies are needed before doctors start using lower doses of tamoxifen to treat patients.

Tamoxifen is a standard therapy for premenopausal women who have had surgery for estrogen receptor (ER) positive breast cancer. It reduces the risk of a cancer recurrence for these women, but also increases their risk for endometrial tumors and blood clots.

Italian researchers from the European Institute of Oncology in Milan sought to compare the effects of tamoxifen at 1 mg/day and 5 mg/day with those of the standard dose of 20 mg/day on breast cancer proliferation.

Their study involving 120 women with ER positive breast cancer who were treated with varying doses of tamoxifen for four weeks prior to their surgery, and 63 women with both ER positive and ER negative breast cancer who did not receive tamoxifen treatment.

The study focused on proliferation marker Ki-67 -- a biochemical marker associated with tumor cell proliferation. At the end of the treatment, production of Ki-67 decreased by an average of 15 percent in all three tamoxifen groups, while it increased 12.8 percent in women in the control group.

But changes in several other blood biomarkers appeared to be more closely linked to the dose of tamoxifen.

"The effects of lower doses of tamoxifen should be assessed further in randomized trials," the researchers concluded.

Other Sources: Journal of the National Cancer Institute