Expert clinicians select genomic assays with nuance. For a patient where a low-risk result is desired to avoid chemotherapy, Oncotype DX may be chosen as it tends to yield more low-risk scores. Conversely, MammaPrint may be used for a chemo-hesitant patient, as it is more likely to return a high-risk result.

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.

Trials like TaylorX and MINDACT use genomic scores to identify patients with early-stage, HR+/HER2- breast cancer who won't benefit from adjuvant chemotherapy. This avoids significant toxicity for two-thirds to over 80% of patients who would have received it under older guidelines, without compromising their outcomes.

Data from the FLEX registry trial, supported by propensity score matching, indicates the survival benefit of adding anthracycline (Adriamycin) to chemotherapy is confined to patients with a MammaPrint High 2 (ultra-high risk) score. Patients in the High 1 group saw no additional benefit.

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.

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.

For premenopausal patients with extensive nodal disease (e.g., N2), the clinical indication for chemotherapy is so strong that even a low-risk genomic score would not be enough to withhold treatment. This highlights the primacy of clinical staging over genomic data in certain high-risk scenarios.

For very high-risk premenopausal patients (e.g., 4+ positive nodes), clinicians may recommend continuing ovarian function suppression beyond the standard 5 years, sometimes advocating for permanent oophorectomy. This is based on clinical experience and data suggesting a more durable blunting of recurrence risk with permanent ovarian ablation.

Citing powerful long-term data from the SOFT and TEXT trials, some oncologists are leaning away from chemotherapy for premenopausal patients with intermediate Oncotype scores (e.g., <25). They argue that the substantial, proven benefits of ovarian function suppression (OFS) may be equivalent to the chemotherapy benefit seen in trials like TAILORx.