The Suppression of Ovarian Function Trial (SOFT)

30 March 2006



The SOFT trial is investigating the role of ovarian function suppression and the role of exemestance in premenopausal women.

Scientific Title

IBCSG 24-02/BIG 2-02: SOFT phase III trial evaluating the role of ovarian function suppression and the role of exemestane as adjuvant therapies for premenopausal women with endocrine responsive breast cancer.


Chemotherapy has been shown to lower the risk of recurrence in some premenopausal women (generally women under the age of 50 years) with breast cancer. In addition, standard treatment also includes hormonal therapy to decrease the chance of the cancer reappearing at a later date.

Hormonal therapy has been shown to help prevent breast cancers coming back after surgery if the breast cancer has hormone receptors. Standard hormonal treatment in younger women has consisted of the oestrogen blocking drug tamoxifen which is usually given for five years. Another class of hormonal drugs called aromatase inhibitors, to which the drug exemestane belongs, has shown promising results in postmenopausal women. Aromatase inhibitors do not work well on their own in premenopausal women, as high levels of oestrogens are present, but are effective when ovarian function is suppressed.

Premenopausal women with breast cancer may also benefit from suppression of the ovaries in order to simulate menopause. This ovarian function suppression can be achieved by either radiotherapy to the ovaries, surgical removal of the ovaries, or by drugs known as the GnRH analogues given as a monthly injection. Supressing the ovaries will reduce the production of oestrogen in the body. Adding an aromatase inhibitor will further lower the level of oestrogen. This overall lowering of oestrogen may be beneficial, as oestrogen can cause breast cancer cells to grow.

The SOFT is being done to see if suppressing ovarian function plus giving tamoxifen is better at preventing the return of breast cancer than giving tamoxifen alone in younger  women. It will also look at whether the hormone drug exemestane plus suppression of the ovaries is better than tamoxifen alone, or tamoxifen plus suppression of the ovaries. It is unclear whether any additional benefit is derived from suppression of ovarian function as no trial has addressed this question to date.

Enrolment: Closed