SAN DIEGOIn a cohort of endometrial cancer patients at M.D. Anderson Cancer Center, those who had previously developed breast cancer and used tamoxifen(Drug information on tamoxifen) did not have a higher incidence of high-risk histologic subtypes, compared with breast cancer patients not receiving tamoxifen, reported Brian M. Slomovitz, MD, at the Society of Gynecologic Oncologists 35th Annual Meeting (SGO abstract 24).
It is well known that tamoxifen reduces the incidence of breast cancer by 50%, but it imposes a two- to sixfold increased risk of developing endometrial cancer, according to a number of studies. Whether cancers associated with tamoxifen are more aggressive is unclear, since the study results have been contradictory on this issue.
"As gynecologic oncologists, we need to know if a history of tamoxifen use affects the clinical course of endometrial cancer in patients with a history of breast cancer," Dr. Slomovitz said.
The study was a retrospective chart review of 1,307 patients with endometrial carcinoma seen at M.D. Anderson between 1990 and 2002. The study identified 77 patients with breast cancer for whom clinical and pathologic information was obtained.
Forty of 77 breast cancer patients (52%) had a history of tamoxifen use; median duration of use was 48 months (range, 6 to 120 months). The median age at diagnosis of endometrial cancer was 65, and was 59 at the time of breast cancer diagnosis. A family history of breast cancer was noted for 29% of patients. There were no significant differences in clinical features between tamoxifen users and nonusers, and the most common presenting symptom was abnormal vaginal bleeding.
Endometrioid Type Prevails
More than two thirds of patients stopped taking tamoxifen within 2 months of their endometrial cancer diagnosis. Patients in whom endometrial cancer developed while taking tamoxifen were more likely to have endometrioid type endometrial cancers than women who stopped the drug for other reasons, Dr. Slomovitz reported, suggesting that tamoxifen appears to play a greater role in these, rather than high-risk, subtypes.