What are your top takeaways in Breast Cancer from ASCO 2024?

1. DESTINY-Breast06

This phase 3 trial randomized patients to either Trastuzumab deruxtecan (T-DXd) vs. physician’s choice chemotherapy (capecitabine, nab-paclitaxel, paclitaxel) in hormone receptor positive HER2 low or HER2 ultralow (any membrane staining) metastatic breast cancer after prior endoc...

1. DB06 - T-DxD has benefit in ultralow HER2 as first line chemo-like option.
2. postMONARCH - abemaciclib has benefit after CDK46i progression
3. A-BRAVE - adjuvant avelumab may have benefit in TNBC
4. AMH in RxPONDER - benefit may be limited to those patients not in ovarian failure, suggesting that chemo ben...

1. Abemaciclib plus fulvestrant vs fulvestrant alone for HR+, HER2- advanced breast cancer following progression on a prior CDK4/6 inhibitor plus endocrine therapy: Primary outcome of the phase 3 postMONARCH trial.
   This is the first phase 3 randomized trial that demonstrated that the CDK4/6 inhibitor ...

1. DESTINY-Breast06: Two big shifts here in this trial for T-DXd, 1) 1st line cytotoxic for HR+ breast instead of 2nd line, and 2) included “ultra-low” HER-2 expression, aka IHC 0 that have some membrane expression. This will include another 20-25% of HR+ patients, so now about 85 or 90% of patients e...

1. postMONARCH - First phase III study of fulvestrant with or without abemaciclib in patients who progressed on prior CDK 4/6 inhibitor and endocrine therapy that showed a statistically significant improvement in progression free survival with c...

Here are my thoughts:

1. DESTINY-Breast06 late-breaking presentation: While I don’t think it would result in us moving all HER2 low metastatic breast cancer patients to TDXd immediately after exhausting endocrine therapy, this data does give us more flexibility to use TDXd for patients who we feel are...

1. Abstract 513 by Choong et al. suggests that ET should still be given to patients with ER-low tumors. There has been a trend to omit ET in these patients. Undoubtedly, the benefit is smaller than in tumors with high ER expression.
   
   
2. Abstract 505 by Kalinsky et al. demonstrated the impact of ovarian fu...

While not immediately practice-changing; a series of abstracts drew attention to a subset of ER+ breast cancers that could benefit from immunotherapy, in the stage II-III setting.

In the June 3rd oral presentations session, the presentation by Dr. @Dr. First Last, “Elucidating the Immune Active Stat...

1. There is an ultralow category that appears to identify patients who benefit from T-DXd. When DB-06 is approved by the FDA, the categorization of HER2 will change again to HER2 3+, negative. For everything else, the question of whether we need to differentiate between ultralow and low categories rem...