Advancements and Evolving Strategies in Breast Cancer Treatment at IBC East

In this episode, CancerNetwork® spoke with breast oncologists Heather McArthur, MD; Erika Hamilton, MD; Hope Rugo, MD; and Paolo Tarantino, MD, PhD, about advances in breast cancer. These developments included recent drug approvals and ongoing research for therapeutic approaches, particularly in the areas of antibody-drug conjugates (ADCs) and CDK4/6 inhibitors, based on presentations they gave at the 25th Annual International Congress on the Future of Breast Cancer (IBC) East in New York City.

Initially, McArthur, Komen Distinguished Chair in Clinical Breast Cancer Research at the Harold C. Simmons Comprehensive Cancer Center, discussed immunotherapy use in high-risk triple-negative and HER2-positive disease, the evolving role of adjuvant CDK4/6 inhibition in HER2-negative breast cancer, and potentially transformative advancements in early breast cancer treatment.

She highlighted the FDA approval for pembrolizumab (Keytruda) in early-stage triple-negative breast cancer, promising clinical trials in estrogen receptor (ER)–positive high-risk early-stage breast cancer, and data from an investigator-initiated trial to treat HER2-positive disease. Additionally, she highlighted an 8.5% improvement in pathological complete response with pembrolizumab added to immunotherapy in the phase 3 KEYNOTE-756 trial (NCT03725059), adding that a further event-free survival benefit may complicate the landscape for CDK4/6 inhibition based on lung and liver toxicities associated with the coadministration of these inhibitors with immunotherapy.¹

McArthur expressed further excitement for ADC-based combinations for triple-negative disease, as well as in the high-risk residual disease setting. In addition, she highlighted potential advancements in de-escalation strategies and further considerations for ADCs in the HER2-positive and hormone receptor (HR)–positive spaces.

Then, Hamilton, director of Breast Cancer and Gynecologic Cancer Research at the Sarah Cannon Research Institute, highlighted emerging therapies for early breast cancer, as well as her use of datopotamab deruxtecan-dlnk (dato-DXd; Datroway) and fam-trastuzumab deruxtecan-nxki (T-DXd; Enhertu) given their recent approvals in various breast cancer subtypes. She also touched upon challenges with respect to the implementation of new therapies for early breast cancer into clinical practice.

She initially highlighted new data from the phase 3 VERITAC-2 trial (NCT05654623) presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting.² Specifically, findings showed that vepdegestrant, an oral proteolysis-targeting chimera (PROTAC), exhibited an efficacy advantage over fulvestrant (Faslodex) in patients with ESR1-mutant ER-positive, HER2-negative advanced or metastatic disease. Moreover, she highlighted data from the phase 3 DESTINY-Breast09 (NCT04784715) of T-DXd in various combinations for patients with HER2-positive metastatic breast cancer.³

Hamilton further highlighted her implementation of T-DXd into clinical practice, citing her use of the agent in patients with metastatic disease, including those with HER2-low and HER2-ultralow breast cancer. She further differentiated dato-DXd from T-DXd, suggesting that they were different classes of drugs due to their different targets: TROP2 vs HER2. She concluded by highlighting an unmet need regarding sustained benefit from endocrine therapy in HR-positive disease, as well as for ADC sequencing and mechanisms of resistance.

Afterward, Rugo, division chief of Breast Medical Oncology, Women’s Cancer Program Director, and professor in the Department of Medical Oncology and Therapeutics Research at City of Hope, discussed efficacy and safety considerations for CDK4/6 inhibitors in early breast cancer treatment. Specifically, she highlighted their high tolerability despite adverse effects and costs associated with their use. Rugo further touched upon a reduction of recurrence rates associated with CDK4/6 inhibition, although longer-term follow-up data were warranted to optimize the duration of therapy and elucidate survival outcomes.

Finally, Tarantino, a research fellow at the Dana-Farber Cancer Institute, concluded by discussing sequencing strategies for ADCs, as well as which breast cancer settings or patient populations will experience the greatest impact with this treatment modality. Tarantino discussed his use of the “sandwich strategy,” where he switches the mechanism of action of treatment after using a TOPO1 ADC. Furthermore, Tarantino highlighted data from the DESTINY-Breast09 and phase 3 ASCENT-04 (NCT06100874) trials, which displayed the enhanced efficacy of 2 ADC combination therapies.⁴ He concluded by discussing future considerations for combining multiple ADCs.

References

1. Cardoso F, O'Shaughnessy J, Liu Z, et al. Pembrolizumab and chemotherapy in high-risk, early-stage, ER+/HER2- breast cancer: a randomized phase 3 trial. Nat Med. 2025;31(2):442-448. doi:10.1038/s41591-024-03415-7
2. Hamilton E, De Laurentiis M, Jhaveri K, et al. Vepdegestrant, a PROTAC estrogen receptor (ER) degrader, vs fulvestrant in ER-positive/human epidermal growth factor receptor 2 (HER2)–negative advanced breast cancer: results of the global, randomized, phase 3 VERITAC-2 study. J Clin Oncol. 2025;43(suppl 17):LBA1000. doi:10.1200/JCO.2025.43.17_suppl.LBA1000
3. Tolaney S, Jiang Z, Zhang Q, et al. Trastuzumab deruxtecan (T-DXd) + pertuzumab (P) vs taxane + trastuzumab + pertuzumab (THP) for first-line (1L) treatment of patients (pts) with human epidermal growth factor receptor 2–positive (HER2+) advanced/metastatic breast cancer (a/mBC): interim results from DESTINY-Breast09. J Clin Oncol. 2025;43(suppl 17):LBA1008.
4. Tolaney SM, de Azambuja E, Kalinsky K, et al. Sacituzumab govitecan (SG) + pembrolizumab (pembro) vs chemotherapy (chemo) + pembro in previously untreated PD-L1–positive advanced triple-negative breast cancer (TNBC): Primary results from the randomized phase 3 ASCENT-04/KEYNOTE-D19 study. J Clin Oncol. 2025;43(suppl 17):LBA109. doi:10.1200/JCO.2025.43.17_suppl.LBA109