Menarini Silicon Biosystems has announced the publication of important findings from the PACE trial, focusing on the clinical utility of counting Circulating Tumor Cells (CTCs) in patients with hormone receptor-positive (HR+), HER2-negative (HER2-) metastatic breast cancer. The results, published in *Clinical Cancer Research*, indicate that CTC enumeration can effectively guide treatment decisions in individuals whose disease has progressed after receiving aromatase inhibitors and CDK4/6 inhibitors.
The secondary analysis of the PACE trial underscores the significance of CTC count in determining whether to escalate or de-escalate treatment for this specific patient group. The trial, which began in 2017, involved 203 patients who were randomized to receive either endocrine monotherapy or combination therapies, including a doublet regimen (endocrine therapy plus a CDK4/6 inhibitor) or a triplet regimen (endocrine therapy, a CDK4/6 inhibitor, and an immune checkpoint inhibitor).
Patients were classified based on their CTC levels: those with fewer than 5 CTCs per 7.5 mL of blood were considered to have indolent disease, while those with 5 or more CTCs were categorized as having aggressive disease. Although the overall population did not show significant differences in progression-free survival among treatment groups, patients classified with aggressive disease experienced a notable reduction in progression risk. Specifically, the risk decreased by 57% for those receiving doublet therapy and by 74% for those on triplet therapy compared to those on monotherapy.
Dr. Lorenzo Gerratana, Associate Professor at the University of Udine and Physician Scientist at IRCCS CRO Aviano, who authored the PACE biomarker analysis, emphasized the findings: “This analysis underscores the value of CTC enumeration to identify HR+/HER2- metastatic breast cancer patients more likely to benefit from intensified therapies after disease progression on first-line treatment.” He noted that patients with aggressive disease demonstrated improved clinical outcomes with combination therapies, whereas those with indolent disease did not derive significant benefits from treatment escalation.
The challenges associated with resistance to CDK4/6 inhibitors highlight the need for reliable biomarkers to inform treatment decisions following disease progression. These findings align with previous research from the STIC trial, which illustrated that treatment decisions guided by CTC counts could lead to improved survival outcomes or allow for treatment de-escalation without adversely affecting survival.
Fabio Piazzalunga, President of Menarini Silicon Biosystems, remarked, “The STIC and PACE trials consistently demonstrate how our CELLSEARCH CTC enumeration can improve patient management in the heterogeneous metastatic breast cancer setting.” He further stated that the test is available for in vitro diagnostic use in Europe and China, and in the United States through their accredited laboratory in Huntingdon Valley, Pa.
CELLSEARCH is recognized as the only CE-marked, clinically validated blood test cleared by the FDA for counting CTCs, aiding physicians in the management of patients with metastatic breast, prostate, and colorectal cancers. It is essential to note that the CELLSEARCH CTC Kit is not approved for use in guiding specific treatment decisions, and the clinical data discussed pertain to investigational use outside its cleared indications.
Menarini Silicon Biosystems, a subsidiary of the Menarini Group, operates from its bases in Bologna, Italy, and Huntingdon Valley, Pa. The Menarini Group is a multinational pharmaceutical, biotechnology, and diagnostics company with a workforce exceeding 17,000 employees across 140 countries.
