SOFT Already Informing Choices in HR+ Breast Cancer

Lidia Schapira, MD


January 15, 2015

Adjuvant Ovarian Suppression in Premenopausal Breast Cancer

Francis PA, Regan MM, Fleming GF, et al; the SOFT Investigators and the International Breast Cancer Study Group
N Engl J Med. 2014 Dec 11. [Epub ahead of print]

Study Summary

Investigators from the International Breast Cancer Study Group studied the additional value of adding ovarian suppression to tamoxifen endocrine therapy for premenopausal women. They randomly assigned 3066 women with early-stage hormone receptor (HR)-positive breast cancer, who were premenopausal at diagnosis or at completion of adjuvant chemotherapy, to receive 5 years of: (1) endocrine therapy with tamoxifen alone, (2) ovarian suppression plus tamoxifen, or (3) ovarian suppression plus the aromatase inhibitor exemestane (Aromasin®).

After a median follow-up of 67 months, the estimated disease-free survival at 5 years was 87% in the tamoxifen plus ovarian suppression group and 85% in the tamoxifen group, a difference that was not considered significant. For women who were at sufficient risk for recurrence to warrant chemotherapy and who regained menses, the addition of ovarian suppression improved disease outcomes, especially for those treated with exemestane.


This much awaited study adds important information to our understanding of the natural history of breast cancer in premenopausal women with HR-positive breast cancer. It can reassure women who are in their forties and have small cancers that tamoxifen alone is sufficient treatment. It does not provide any data on the role of Oncotype DX panels (now commonly used) in helping decide who ought to receive chemotherapy in the first place; conversely, Oncotype panels cannot fully reassure us that it is fine to avoid chemotherapy in any premenopausal woman with node-positive cancer. As with any other important adjuvant study of HR-positive breast cancer, by the time we have answers, we already have new clinical practices that have changed how we practice. Since publication of the Suppression of Ovarian Function Trial (SOFT) in the New England Journal of Medicine, I have already given hard copies or emailed copies to many patients. At least one of my patients had already poured through the Kaplan-Meier curves online before her clinic visit.

The study is well presented and clearly written and helps us in those situations when we are sufficiently worried about the risk for relapse to recommend chemotherapy: patients who are aged 35 years or younger, have high-grade tumors, or have node-positive disease. For those patients, I think ovarian suppression and consideration of an aromatase inhibitor merits discussion. And while we are sorting through options for adjuvant endocrine therapy, remember that in the MA 17 study[1] of extended sequential adjuvant endocrine therapy, the women who were premenopausal at diagnosis and took 5 years of tamoxifen and then reached menopause and were randomly assigned to 5 years of aromatase inhibition had improved outcomes (even those who were node negative).


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