Oct. 17, 2000 NEW YORK, October 15, 2000 -- Women taking tamoxifen to prevent breast cancer receive no benefit from routine screening for endometrial cancer, a known risk associated with the drug. In an eight-year study conducted at Memorial Sloan-Kettering Cancer Center, 111 breast cancer patients were screened with an endometrial biopsy (EMB) at the beginning of their treatment with tamoxifen with additional biopsies over a five-year period. The researchers reported no benefit to routine screening in their study published in the October 15, 2000 Journal of Clinical Oncology.
"Women with breast cancer who are taking tamoxifen should be advised that regular uterine biopsies are no more effective at detecting early endometrial cancer than is the presence of abnormal vaginal bleeding," said Richard Barakat, MD, associate chief of the Gynecology Service at Memorial Sloan-Kettering and principal investigator of the study. "This should prevent the hundreds of thousands of women now on the drug and the 80,000 women who start using it each year from undergoing unnecessary, invasive tests to detect this rare cancer."
Tamoxifen is reported to cause endometrial cancer at a rate of two per 1,000 women per year with a mortality rate of 15 percent. The question raised was how best to screen the breast cancer patients treated with this drug. "Because the risk of developing endometrial cancer due to tamoxifen is small and this cancer is highly curable if detected early, we attempted to see if we could improve on these low rates through effective screening," said Dr. Barakat. "We found that when the cancer does develop, patients can detect it because of bleeding. The screening with uterine biopsies added nothing."
To evaluate whether endometrial biopsy was the most effective screening method, 159 women who were beginning tamoxifen therapy for breast cancer confined to the breast and axillary lymph nodes were entered into a prospective study between October 1991 and September 1998 at Memorial Sloan-Kettering. Their median age was 50. An office endometrial biopsy was obtained when the tamoxifen was initiated and at six-month intervals for a period of two years. Three subsequent annual EMB's were recorded for each patient totalling a five-year surveillance. The 111 who were subsequently eligible for the study received a total of 635 EMB's with a median surveillance time of 36 months. Fourteen patients (12.6 percent) underwent dilation and curettage (D&C) for suspected abnormalities but none of these patients were found to have cancer.
"Breast cancer patients are concerned about how best to be screened for the low risk of developing endometrial cancer, a known side effect of tamoxifen therapy," said Teresa Gilewski, MD, an oncologist with the Breast Service at Memorial Sloan-Kettering and one of the study's authors. "Patients taking tamoxifen should be carefully followed by their physician and instructed to report any episode of abnormal vaginal bleeding immediately. Should they develop bleeding, they would undergo a biopsy with further evaluation, if necessary. At this time, however, there is no evidence to clearly support routine endometrial biopsies to screen asymptomatic patients."
Breast cancer specialists agree that the 0.2 percent annual risk of developing endometrial cancer should not prevent breast cancer patients from taking tamoxifen. "This study reassures us that screening for a rare event such as uterine cancer is not helpful," said Clifford Hudis, MD, chief of the Breast Service at Memorial Sloan-Kettering. "Therefore, women with invasive breast cancer who take tamoxifen, a time-tested drug that is responsible for saving hundreds of thousands of lives, should not feel compelled to undergo excessive testing looking for endometrial cancer."
Memorial Sloan-Kettering Cancer Center is the world's oldest and largest private institution devoted to prevention, patient care, research, and education in cancer. Throughout its long distinguished history, the Center has played a leadership role in defining the standard of care for patients with cancer.
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