ASCO20: Biomarker Expression and Outcomes After Adjuvant Treatment in Breast Cancer
Posted: Thursday, June 4, 2020
PIK3CA mutation status did not affect invasive disease–free survival of patients with breast cancer who received either adjuvant trastuzumab emtansine (T-DM1) or adjuvant trastuzumab, according to biomarker data from the phase III KATHERINE trial. However, several other biomarkers—HER2, PD-L1, and checkpoint inhibitors—did affect invasive disease–free survival—but only with trastuzumab therapy and not with T-DM1 treatment. Carsten Denkert, MD, of Philipps University Marburg, Germany, and colleagues presented these findings during the ASCO20 Virtual Scientific Program (Abstract 502).
“Trastuzumab emtansine benefit appeared to be independent of all biomarkers assessed,” wrote the authors. “These exploratory analyses provide the first data on the relationship between biomarker expression in residual disease after HER2-targeted therapy and outcomes.”
This study focused on biomarker data from the KATHERINE trial, which compared adjuvant T-DM1 with trastuzumab to treat residual invasive disease in patients who had already received neoadjuvant therapy for HER2-positive breast cancer. In this study, the authors analyzed PIK3CA mutation status in 1,363 patients, and tissue samples were collected at surgery from 815 patients. They identified PIK3CA hotspot mutations and looked for HER2, PD-L1, CD8, and predefined immune signatures using RNA analysis.
The authors observed no effect of PIK3CA mutation status on invasive disease–free survival in either treatment group. Across several different biomarkers, biomarker status did not impact invasive disease–free survival within the T-DM1 treatment arm but did impact survival within the trastuzumab arm. This also was true for HER2 expression, PD-L1 expression, and in the checkpoint inhibitor biomarker subgroups. Higher HER2 expression was associated with worse outcomes within the trastuzumab arm, and higher PD-L1 expression was associated with better outcomes.
Disclosure: The study authors’ disclosure information may be found at coi.asco.org.
