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Benefits of Hormone Replacement on Breast Cancer Survival Are Durable: Presented at ASBS

By Carole Bullock

NEW YORK -- May 9, 2008 -- Breast cancer survival rates for users of hormone replacement therapy (HRT) continue to be significantly better after at least 5 years compared with nonusers of HRT for at least 5 years, researchers reported here at the 9th Annual Meeting of the American Society of Breast Surgeons (ASBS).

In a previous study that evaluated the 2.5-year results in women who used HRT and in nonusers, the researchers observed that women who used HRT lived longer and that tumours detected in these women were significantly smaller, lower grade, and more often node negative.

Now, the study's 5-year results show that survival is maintained over the long term, with survival rates of 92% for HRT users versus 84% for never-users (P = .02), reported Rodney F. Pommier, MD, Professor of Surgery, Division of Surgical Oncology, Oregon Health & Science University, Portland, Oregon.

Long-term use of HRT was associated with a significantly higher probability of having a tumour detection by mammography (P = .02), even though the frequency of screening mammography between HRT users and never-users was similar.

Among patients with mammographically detected tumours, HRT users had 100% survival compared with 90% for never-users (P =.03). And no differences in survival were seen between HRT regimens, Dr. Pommier said in an oral presentation on May 3.

This significant survival difference between HRT users and never-users with mammographically detected tumours indicates that this is not due to better screening among HRT users; rather, it is consistent with a favourable biological effect of hormones on the tumours, he noted in an interview.

"Patients with greater than 9 years of HRT also had 100% survival regardless of mode of tumour detection," he added.

In complementary basic-science experiments, the authors measured the effects of oestrogen and medroxyprogesterone acetate (MPA) on breast cancer cells in vitro.

For the in vitro studies, oestrogen-receptor-positive and progesterone-receptor-positive breast cancer cell lines and those with oestrogen-receptor-positive and progesterone-receptor-negative cell lines were treated for 5 days with oestrogen (1-10 nM) and/or MPA (0.1-250 nM).

"The addition of MPA did not change the effects seen with oestrogen alone," he said. "Many of the concentrations and combinations were growth inhibitory for breast cancer cells. Our in vitro results support our clinical findings that [oestrogen] or [oestrogen] plus MPA do not worsen clinical outcomes."


[Presentation title: Improved Breast Cancer Survival of HRT Patients, Regardless of Regimen or Length of Therapy, Is Durable After an Additional 5 Years of Follow-Up. Oral Presentation]

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