The Destiny Breast 11 trial compared a new drug to a chemotherapy regimen (ACTHP) that many US oncologists no longer use. This choice of a less common control arm makes it difficult for them to directly compare the new treatment's efficacy against their own current standard (TCHP), complicating adoption.

The Serena 6 trial's PFS2 data is difficult to interpret because only 13% of the control arm received a next-generation oral SERD post-progression. This low crossover rate makes it hard to definitively conclude if switching to camazestrant early is superior to switching later, as the control group's subsequent treatment was not the modern standard of care.

The LIDERA trial's early, robust success with the oral SERD giredestrant in adjuvant therapy is surprising. In the metastatic setting, these drugs primarily benefit tumors with ESR1 mutations, which are acquired after therapy and rare at diagnosis. This paradoxical result suggests a different mechanism of action in early-stage disease and necessitates longer follow-up to confirm the finding.

Ladera showed a significant benefit for geridesterant over standard endocrine therapy in early breast cancer with an efficacy signal similar to initial readouts for CDK4/6 inhibitors. Since CDK4/6 inhibitors were excluded, this creates a clinical debate: are these treatments interchangeable, sequential, or for different populations?

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.

While the Lidera trial showed a benefit for the oral SERD giredestrant in the adjuvant setting, experts advise caution before changing practice. The trial's control arm (standard endocrine therapy) does not reflect the current standard of care for high-risk patients, which now includes CDK4/6 inhibitors, making a direct comparison difficult.

The Phase 3 Ladera study found gerodestrin not only reduced the risk of recurrence by 30% over standard endocrine therapy but also caused fewer treatment discontinuations due to side effects. This dual benefit of superior efficacy and improved tolerability represents a significant potential advancement for patients with ER-positive early breast cancer.

While the LADERA study showed a benefit for oral SERD gerodestrant over standard endocrine therapy, its applicability is questionable. In the metastatic setting, adding an oral SERD to a CDK inhibitor did not show a statistically significant benefit over an AI plus CDK, raising doubts about its added value in the adjuvant CDK era.

Unlike tamoxifen, oral SERDs likely cannot be used as a monotherapy in premenopausal women. The pre-CoAbera trial failed to show gerodestrant alone was sufficient and was associated with ovarian cysts and higher estradiol. This suggests ovarian function suppression (OFS) is a necessary partner for oral SERDs to be effective in this younger patient population.