Addition of Ovarian Suppression to Tamoxifen in Select Early Breast Cancer Patients

The results of a phase 3, randomized trial showed that adding ovarian suppression to tamoxifen improved disease outcomes in specific populations of premenopausal women with hormone receptor-positive (HR+) early breast cancer [N Engl J Med. 2014; DOI:10.1056/NEJMoa1412379].

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“For women with [HR+] early breast cancer who received adjuvant chemotherapy and remained premenopausal (average age of 40 years), adding ovarian suppression to adjuvant tamoxifen can reduce the risk of recurrence compared with tamoxifen alone,” said the study’s lead author, Prudence A. Francis, MD, associate professor, head of medical oncology, breast service, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia, in an interview with First Report Managed Care.

However, for women who did not receive adjuvant chemotherapy, the study found no benefit to the addition of ovarian suppression and found that these women did very well with tamoxifen alone.

In the SOFT [Suppression of Ovarian Function Trial] study, 2033 premenopausal women with HR+ early breast cancer were included in an intention-to-treat primary analysis that compared disease-free survival between patients randomized to receive 5 years of tamoxifen alone (n=1018) or tamoxifen plus ovarian suppression (n=1015). Along with documented premenopausal status, patients included in the study had operable breast cancer with tumor expressing estrogen or progesterone in at least 10% of cells, had undergone total mastectomy with optional radiotherapy or breast-conserving surgery with radiotherapy, and had undergone axillary dissection or sentinel-node biopsy.

Patients were stratified according to prior treatment with chemotherapy, with 949 patients receiving no chemotherapy and 1084 receiving prior chemotherapy and remaining premenopausal.  
At a median follow-up of 67 months, the study found no significant difference in the estimated 5-year disease-free survival between the patients treated with tamoxifen alone (84.7%) and those treated with tamoxifen plus ovarian suppression (86.6%; hazard ratio [HR], 0.83; 95% confidence interval [CI], 0.66-1.04; P=.10).

However, in patients who received prior chemotherapy, the rate of breast cancer remission at 5 years was greater in those who received the addition of ovarian suppression to tamoxifen (82.5%) compared to the those who received tamoxifen alone (78%; HR, 0.78; 95% CI, 0.6-1.02).

The study also compared disease-free survival in a group of 1014 women who received exemestane plus ovarian suppression compared to tamoxifen alone and found that exemestane reduced the risk of recurrence even further than tamoxifen plus ovarian suppression.

The rate of breast cancer remission at 5 years was 85.7% in the patients treated with exemestane plus ovarian suppression compared to 78% in those treated with tamoxifen alone (HR, 0.65; 95% CI, 0.49-0.87).

“Until this study, it had been uncertain whether adding ovarian suppression provided any benefit in women who receive adjuvant chemotherapy and tamoxifen,” said Dr. Francis, adding that the current results indicate the importance of ovarian suppression in the treatment for some premenopausal women with early breast cancer.—Mary Beth Nierengarten