SAN ANTONIO — Tamoxifen does not appear to increase the risk of either stroke or acute MI in women with breast cancer, Ann M. Geiger, Ph.D., reported at a breast cancer symposium sponsored by the Cancer Therapy and Research Center.
Previously, two large, randomized National Surgical Adjuvant Breast and Bowel Project studies—the P-1 Breast Cancer Prevention Trial and the B-24 trial involving treatment of patients with ductal carcinoma in situ—had suggested tamoxifen increased stroke risk. But such randomized trials are vulnerable to volunteer bias.
Dr. Geiger's nested case-control population-based study involving 532 breast cancer patients in a large HMO concluded that stroke risk should not enter into clinical decision-making about tamoxifen use in breast cancer patients.
On the other hand, although there were signals in prior studies that tamoxifen might have a cardioprotective effect, no such benefit was found in a separate Kaiser study involving 396 women with breast cancer. In this study, use of the nonsteroidal hormone didn't affect MI risk, said Dr. Geiger of Kaiser Permanente of Southern California, Pasadena.
What does matter a great deal in terms of preventing stroke and MI in women with a history of breast cancer is appropriate management of hypertension and diabetes, she stressed. In the Kaiser studies, hypertension that required medication was associated with 2.1-fold increased risk of MI and a 2.0-fold risk of stroke in breast cancer survivors. Diabetes requiring medication boosted stroke risk 2.4-fold and MI risk 3.0-fold.
Other key findings in the pair of studies were that chemotherapy for breast cancer was an independent risk factor for stroke, conferring a 2.7-fold increased risk, while radiation therapy was associated with a subsequent 2.9-fold increased risk of MI, she said
One study involved 179 Kaiser patients with a first invasive breast cancer followed by a first stroke during 1980–2001, along with 353 matched controls who were treated for breast cancer but did not have a stroke. Although the study identified chemotherapy as a risk factor for stroke, it wasn't possible to differentiate the impact of the various chemotherapy regimens used.
The other study involved 134 patients with invasive breast cancer who subsequently experienced a first MI and 262 matched controls with breast cancer who didn't.
In the two studies, neither cumulative dose of tamoxifen, duration of use, nor length of time since use was associated with stroke or MI.
Tamoxifen has been the leading hormonal therapy for patients with estrogen receptor-and/or progesterone receptor-positive breast cancer for nearly 3 decades. It has been shown to decrease the risks of ipsilateral recurrences as well as contralateral breast cancer.