Long-term follow-up from the SOFT study shows adding ovarian function suppression (OFS) for premenopausal women under 35 with HR-positive breast cancer yields an 18% absolute improvement in breast cancer-free interval. The speaker notes these gains are unprecedented since the introduction of trastuzumab, highlighting OFS as a critical, high-impact intervention for this specific patient group.

Final 15-year data from the SOFT/TEXT trials reveal that the survival advantage of adding ovarian function suppression (OFS) to an AI is not uniform. The benefit is most pronounced in the highest-risk premenopausal patients, particularly those under 35 or with grade 3 disease, for whom tamoxifen alone is considered inadequate.

Positive data from both DESTINY-Breast09 (TDXD-based) and PATINA (CDK4/6i maintenance) create a new dilemma. With similar PFS outcomes, the first-line choice for metastatic HER2+/HR+ patients now hinges on toxicity profiles and patient preference rather than a single efficacy winner.

In premenopausal patients, chemotherapy's observed benefit may be an indirect effect of inducing menopause, rather than its cell-killing properties. The ongoing OFFSET trial is testing if optimizing endocrine therapy with ovarian suppression can achieve the same risk reduction as chemotherapy, potentially avoiding chemo's side effects entirely for this group.

Experts assert that chemotherapy should not be used as first-line treatment for HR-positive metastatic breast cancer. Clinical trials show a CDK4/6 inhibitor with endocrine therapy provides better outcomes and tolerability than multi-agent chemotherapy, even for patients with aggressive, symptomatic visceral metastases, challenging the traditional use of chemo for rapid response.

Even within recent major clinical trials like HER2CLIMB-05, less than half of eligible hormone receptor-positive patients received endocrine therapy. This highlights a critical and widespread gap in clinical practice, as this treatment adds significant benefit.

While the SOFT trial established a five-year standard for ovarian function suppression (OFS), new registry data indicates that continuing OFS beyond five years, often towards 10 years or natural menopause, further reduces recurrence risk. This evidence supports considering a longer duration of OFS for many premenopausal women to maximize long-term, robust benefits.

While the HER2 pathway is the dominant driver for achieving an initial tumor response in HER2+/HR+ disease, targeting the ER pathway is critical for maintaining that response and achieving long-term benefit. This dual-targeting benefit becomes more apparent over extended periods, as seen in the Affinity trial.

Uniquely, the EMPRIS window study in premenopausal patients showed geridestran monotherapy was more effective at suppressing proliferation than tamoxifen without adding an LHRH agonist. This challenges the standard practice of mandatory ovarian function suppression and could simplify treatment for younger women.