medwireNews: Postmenopausal women who use vaginal estrogen therapy (VET) or menopausal hormone therapy (MHT) after surgery for early-stage, estrogen receptor-positive breast cancer may not have an increased risk for recurrence or death, suggest Danish investigators.
However, the team identified a small but significant increased risk for recurrent breast cancer among the subgroup of VET users who were taking adjuvant aromatase inhibitors (AIs), albeit without an accompanying increased risk for mortality.
“For early-stage [breast cancer] patients receiving adjuvant AIs, [VET] should be used with caution,” advise Søren Cold, from Odense University Hospital, and co-authors in Journal of the National Cancer Institute.
The researchers collated information from a Danish national cohort of 8461 postmenopausal women aged 35–95 years who had not used VET or MHT before their breast cancer diagnosis between 1997 and 2004. The patients had not received chemotherapy for their early-stage disease but were assigned to receive 5 years of adjuvant tamoxifen, an AI, both treatments in sequence, or no adjuvant therapy.
Overall, 1957 of these women received VET and 133 MHT alone or alongside VET after the breast cancer diagnosis, while 6371 did not receive any hormone therapy, Cold et al say. They note that compared with hormone therapy users, women who were not given VET or MHT were older, had larger tumors, and were more likely to have lymph node involvement.
Over a median 9.8 years of potential follow-up, 16% of the women had recurrent breast cancer, including 111 patients who had used VET, 16 who had used MHT with or without VET, and 1206 who had never received hormone therapy.
After adjusting for age, tumor size, histology, nodal status, and other risk factors, the risk for recurrence did not significantly differ between patients who had received VET or MHT compared with women who used neither treatment.
But the risk for recurrence was significantly higher among women who used VET and an AI (alone or in sequence with tamoxifen) compared with nonusers, with an adjusted hazard ratio of 1.39
Overall survival analysis did not identify an increased risk for mortality among VET or MHT users versus nonusers, regardless of which adjuvant therapy they received. The absolute 10-year rates of overall survival were 79.5%, 80.5%, and 73.8%, respectively.
Recognizing that “[t]he treatment of [genitourinary syndrome of menopause] in [breast cancer] survivors remains a challenge,” the researchers suggest patients consider nonhormonal options and VET if these are “insufficient.”
They explain: “Because we did not observe increased risk of recurrence in VET-treated patients receiving tamoxifen, switching to tamoxifen after 2 to 3 years of an AI may be considered for women initiating VET.”
Commenting on the research to the press, Paul Pharoah, from the University of Cambridge in the UK, said the study findings “are reassuring for women who get menopausal symptoms as a result of treatment of their breast cancer with tamoxifen.”
But he emphasized that the researchers “cannot definitively rule out a small increase in risk as all observational studies are prone to some forms of bias and the interpretation of the results can be difficult.”
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