Dr. O’Regan on the SOFT Trial in Premenopausal Women With HR+ Breast Cancer

Ruth M. O’Regan, MD, professor, chair, Charles Ayrault Dewey Professorship of Medicine, Department of Medicine, the University of Rochester, physician-in-chief, Strong Memorial Hospital, associate director, Education and Mentoring, the Wilmot Cancer Institute at University of Rochester, discusses the significance of the Breast Cancer Index (BCI) as a prognostic tool, as well as the investigation of the phase 3 SOFT trial (NCT00066690), for patients with early-stage, hormone receptor (HR)-positive breast cancer.

The phase 3 SOFT trial utilized the BCI to predict the efficacy of ovarian function suppression plus tamoxifen (Nolvadex) or exemestane (Aromasin) compared with tamoxifen monotherapy in premenopausal women undergoing adjuvant endocrine therapy for early-stage, HR-positive breast cancer who had previously undergone surgery. In data presented during the 2022 San Antonio Breast Cancer Symposium, moreover, the BCI was found toidentify these patients who would derive benefit from the addition of ovarian function suppression.

The genomic testing was performed on previously obtained tumor blocks from patients enrolled in the study to predict patient benefit and outcomes with extended tamoxifen administration, O'Regan states. The BCI incorporated the molecular grade index, which indicates the expression of several key cell-cycle proliferation genes, and the HOXB13/IL17BR (H/I) index ratio, which is predictive of adjuvant endocrine therapy duration, O’Regan adds.

Results from the SOFT trial showed that the BCI ratio increased regardless of node positivity or negativity, O’Regan continues, adding that these findings indicate that the BCI is a reliable prognostic for the risk of late-disease recurrence. Additionally, a low H/I score successfully predicted patient benefit from ovarian function suppression with either aromatase inhibitors or tamoxifen, while a high H/I score was not found to be predictive, O’Regan notes.

Ultimately, these findings support the BCI as the first reliable predictive test for the risk of recurrence and response to adjuvant treatment options in this patient population, O’Regan concludes.