Estrogen Replacement Therapy After Localized Breast Cancer: Clinical Outcome Of 319 Women Followed Prospectively

Reviewers: Kenneth Blank, MD
Source: Journal of Clinical Oncology, Vol. 17, Issue 5 (May), 1999: 1482

Introduction

With breast cancer screening programs detecting more young women with early stage breast cancer, the number of breast cancer survivors is increasing every year. When these survivors reach menopause they are faced with a difficult decision regarding whether or not to take estrogen replacement therapy. For many years, estrogen replacement therapy has not been recommended for breast cancer survivors on the belief that estrogen will initiate tumor re-growth. However, the positive effects of estrogen replacement therapy on the cardiovascular and skeletal systems are indisputable. A report from the MD Anderson Cancer Center in the May issue of the Journal of Clinical Oncology explores the issue of estrogen replacement therapy for breast cancer survivors.

Methods

319 women previously treated for stage I or II breast cancer that had undergone menopause were registered on this study. All women were either estrogen receptor negative or unknown. All of the women were offered to participate in an ongoing randomized prospective trial comparing estrogen replacement therapy to observation. Sixty-two women agreed to enter the randomized trial (and were also registered on this study), 20 of who were assigned to receive estrogen replacement therapy. Of the 257 declining enrollment in the randomized study, 10 were dosed estrogen replacement therapy for severe menopause-related symptoms. In total, 30 women (20 as part of the randomized trial and 10 for symptoms) received conjugated estrogen (0.625mg on days 1-25 of each month) without progesterone and 280 women received no therapy (the control group). Both groups were prospectively followed with respect to recurrent or new breast cancer.

Results

The two groups did not differ with respect to breast cancer prognostic factors. Specifically, the two groups were similar in age at diagnosis, disease-free interval, and number of positive lymph nodes, tumor size, and estrogen receptor status. One difference between the two groups was that the group receiving estrogen replacement therapy was followed for significantly longer period of time (55 months vs. 36 months).

The incidence of a new breast cancer was similar between the two groups. Only one patient on estrogen replacement therapy developed a new breast cancer compared with 14 patients in the control group. No patient in either group experienced a recurrence of the original tumor.

Conclusions

This study , although small and not randomized, provides evidence that estrogen replacement therapy in women cured of localized breast cancer does not increase the risk of a new or recurrent breast cancer. This finding corroborates work from other institutions showing estrogen replacement therapy does not have an adverse effect on breast cancer outcome. Several large randomized trials comparing observation to estrogen replacement therapy have been initiated, and are beginning to accrue patients, but the results from these studies are not expected for many years. Therefore, patients and physicians must rely on small non-randomized trials such as this in making this difficult decision.