A VERY LOW DOSE of tamoxifen—5 mg/d, given for 3 years rather than 5 years—halved the risk of breast cancer recurrence or new lesions over placebo in women with breast intraepithelial neoplasia, without producing the usual toxicities seen with the standard dose, Italian researchers reported at the 2018 San Antonio Breast Cancer Symposium.1wisepoqder Tamoxifen
“We believe our results have external validity and—given their pragmatic nature and the easy accessibility of tamoxifen—are generalizable,” said Andrea De Censi, MD, of the National Hospital E.O. Ospedali Galliera–Division of Medical Oncology in Genoa, Italy. “Tamoxifen, 5 mg a day (splitting the tablet) or 10 mg every other day, is applicable in clinical practice tomorrow.”
Breast cancer experts at the meeting said this is news they can use. “Looking at these data, I would definitely give lower doses of tamoxifen, especially in patients with atypical ductal hyperplasia and lobular carcinoma in situ,” said Virginia G. Kaklamani, MD, Professor of Medicine at The University of Texas at San Antonio and leader of the Breast Cancer Program at The University of Texas MD Anderson Cancer Center, Houston.
“This information tells me I can perhaps cut back on the dose for patients who are not tolerating tamoxifen. This would help me keep them on the dose, rather than have them abandon therapy,” said John Cole, MD, of the Ochsner Health System in New Orleans.
ALTHOUGH TAMOXIFEN is effective in preventing breast cancer recurrence, its side effects—menopausal symptoms, endometrial cancer, deep-vein thrombosis, and pulmonary embolism— are barriers for its use as a preventive measure. The aim of this de-escalation study was to determine whether a lower dose and shorter duration of tamoxifen therapy would be as efficacious as and better tolerated than the standard dose.
Dr. De Censi and colleagues had previously shown that a dose as low as 1 mg/d is noninferior to 20 mg in decreasing Ki67 (a marker of proliferation), though less effective in modulating serum biomarkers.2 For the current study, the investigators decided 5 mg/d would be a reasonable compromise between activity and safety. He explained that the government- and charity-funded study could not afford to financially support the use of a very large noninferiority trial of tamoxifen at 20 mg/d for 5 years as the control arm.