Dr Mouabbi on Data From the CompassHER2 pCR Trial in HER2+ Breast Cancer

“The results were very encouraging. [Following] only 4 cycles of THP, without carboplatin, [the] pCR rate in the overall population [was] 43.8%. TCHP, which is what we currently use [as the standard of care] in the US, [produces] a pCR rate of approximately 60% in the overall population. [The rates for THP vs TCHP] were fairly close, [but THP has] a lot less chemotherapy.”

Jason Aboudi Mouabbi, MD, an assistant professor in the Department of General Oncology and Department of Breast Medical Oncology, Division of Cancer Medicine, at The University of Texas MD Anderson Cancer Center, discussed data from the phase 2 EA1181/CompassHER2 pCR trial (NCT04266249) of neoadjuvant multi-agent chemotherapy in patients with stage II or III HER2-positive breast cancer.

Findings from CompassHER2 pCR presented during the 2025 ASCO Annual Meeting showed that patients in the overall population (n = 2141) achieved a pathologic complete response (pCR) rate of 43.8% (95% CI, 41.6%-45.9%); these results were encouraging because they were achieved with 4 cycles of paclitaxel or docetaxel, plus trastuzumab (Herceptin) and pertuzumab (Perjeta; THP), without carboplatin, Mouabbi began. THP plus carboplatin (TCHP), which is the regimen typically chosen to treat patients in the US, has a pCR rate of approximately 60%, meaning that THP was shown to yield a similar rate with much less chemotherapy, he added.

Moreover, patients with estrogen receptor (ER)–positive, HER2-positive disease (n = 774) achieved a pCR rate of 63.7% (95% CI, 60.2%-67.1%) and those with ER-positive, HER2-positive disease (n = 1337) had a pCR rate of 32.5% (95% CI, 30%-35%), Mouabbi said. The patient population of CompassHER2 pCR included patients with ER-positive, HER2-positive disease at a rate of 62%, which may have contributed to the lower pCR rate in the overall population compared with the historical control of TCHP, he concluded.