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SABCS 2014: Ovarian Suppression Added to Hormonal Therapy Reduces Risk of Recurrence in Some Premenopausal Women

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Key Points

  • Ovarian function suppression reduced risk of breast cancer recurrence when added to adjuvant tamoxifen in women with premenopausal hormone receptor–positive breast cancer treated with chemotherapy.
  • Women in this cohort had an even lower risk of recurrence if they received exemestane plus ovarian function suppression.
  • In women who did not need chemotherapy, 5 years of tamoxifen was sufficient to reduce recurrence risk, and ovarian function suppression is not advised in this group.

Results of the large international SOFT trial present a convincing argument for the addition of ovarian function suppression to adjuvant hormonal therapy to reduce the risk of recurrence in premenopausal women with hormone receptor–positive breast cancer at high enough risk to be treated with chemotherapy. In the cohort of premenopausal women who received chemotherapy, ovarian suppression plus exemestane achieved an even more robust reduction in risk of recurrence than ovarian suppression plus tamoxifen.

In the cohort of women not requiring chemotherapy, tamoxifen alone was sufficient to reduce risk of recurrence.

“I believe this trial is practice-changing. If I see a woman under age 35 with hormone receptor–positive breast cancer, I will know how to advise her. I also will feel more comfortable with tamoxifen alone in a woman age 46 or older with small, low-risk breast cancer,” stated lead author Prudence Francis, MD, Head of Breast Medical Oncology at Peter McCallum Cancer Centre, Melbourne, Australia. The results were presented at the 2014 San Antonio Breast Cancer Symposium (Abstract S3-08) and published online in The New England Journal of Medicine.

SOFT Trial

SOFT is the largest trial to be conducted on ovarian suppression in premenopausal women with breast cancer. The trial was designed to assess the value of ovarian suppression in 3,047 young women with hormone receptor–positive breast cancer treated with 5 years of adjuvant therapy with tamoxifen or exemestane vs tamoxifen alone. Women randomly assigned to ovarian suppression in either arm had the choice of monthly injections of triptorelin (Trelstar), surgical removal of the ovaries, or radiation.

These treatments were compared in two different groups of women: those women who needed chemotherapy (younger age, higher-risk tumors, larger tumors, more likely to be node-positive) and those who didn’t. Women who had chemotherapy entered the trial 8 months postchemotherapy while those who didn’t entered the trial soon after surgery. At a median follow-up of 5.6 years, there was no overall benefit for the addition of ovarian suppression; 5-year event free survival was 84.5% with tamoxifen alone vs 86.6% for the combination of tamoxifen alone, which was not statistically significant.

Significant Reduction in Risk

However, in the cohort that remained premenopausal after chemotherapy (average age, 40 years), ovarian suppression added to tamoxifen achieved a 22% reduction risk of recurrence vs tamoxifen alone. The combination of exemestane plus ovarian function suppression was even better, with a 35% risk reduction for recurrence vs tamoxifen alone. The 5-year event-free survival was 78% for tamoxifen alone, 82.5% for tamoxifen plus ovarian function suppression, and 85.7% for exemestane plus ovarian function suppression.

“In women under age 35, one in three women on tamoxifen alone—the standard of care—had further recurrence within 5 years compared with one in six for exemestane plus ovarian function suppression,” Dr. Francis stated.

Looking at the cohort of women who did not receive chemotherapy (average age, 46 years), they did well in all three study arms. Five-year event-free survival was 95.8% with tamoxifen alone, 95.1% with tamoxifen plus ovarian suppression, and 97.1% with exemestane plus ovarian suppression.

“In this older group of women who did not have chemotherapy, there is no reason to add ovarian suppression. The average age is 46 years, and some of these women will go into menopause soon,” Dr. Francis said.

The SOFT trial was supported by Pfizer, the IBCSG, and the National Cancer Institute, among others. Dr. Francis reported no potential conflicts of interest.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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