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Clarifying the Clinical Utility of CELLSEARCH® in Metastatic Breast Cancer

Menarini Silicon Biosystems, a frontrunner in the field of cell-based liquid biopsy technology, has recently published pivotal findings from the PACE trial in the esteemed Clinical Cancer Research. This multicenter phase II study aimed to delve into the potential clinical implications of counting Circulating Tumor Cells (CTCs) in patients diagnosed with hormone receptor-positive (HR+), HER2-negative (HER2-) metastatic breast cancer. By analyzing data from patients who experienced disease progression following treatment with aromatase inhibitors paired with CDK4/6 inhibitors, the study provides compelling evidence on how CTC counts can uniquely guide therapeutic decisions.

During the PACE trial, a total of 203 participants were randomized to either receive endocrine monotherapy or a combination therapy—either a doublet (endocrine therapy along with a CDK4/6 inhibitor) or a triplet regimen (adding an immune checkpoint inhibitor to the doublet). The analysis categorized patients based on their CTC counts: those with fewer than five CTCs per 7.5 mL of blood were classified as experiencing indolent disease, while those with five or more CTCs faced aggressive forms of the illness.

Interestingly, the overall progression-free survival rates showed little difference between treatment groups across the study population. However, a stark benefit was highlighted for those with an aggressive profile; patients exhibiting five or more CTCs had a 57% reduction in the risk of disease progression when treated with doublet therapy and an astonishing 74% risk reduction when on triplet therapy, compared to those receiving only endocrine monotherapy.

Dr. Lorenzo Gerratana, the lead author from the University of Udine and a Physician Scientist at IRCCS CRO Aviano, emphasized the implications of these findings. He stated, “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.” The analysis suggests that while aggressive disease patients markedly benefited from combination therapies, those with indolent disease showed no significant advantages from the escalated treatment protocols.

As the understanding of mechanisms behind CDK4/6 inhibitor resistance remains incomplete, the identification of reliable biomarkers such as CTC counts is increasingly vital for guiding treatment decisions in the face of disease progression. The recent insights from the PACE trial echo the findings of the earlier STIC trial, which also advocated for treatment decisions to be informed by CTC counts, revealing a possibility for improved survival outcomes or effective treatment de-escalation without compromising patient health.

Fabio Piazzalunga, the President of Menarini Silicon Biosystems, reflected on these findings, affirming, “The STIC and PACE trials consistently demonstrate how our CELLSEARCH CTC enumeration can improve patient management in the heterogeneous metastatic breast cancer setting.” He elaborated on the availability of this advanced test in Europe and China, alongside a certified laboratory in the U.S. committed to enhancing physicians' decision-making processes.

With its distinction as the only CE-marked, clinically validated blood test cleared by the FDA for CTC counting to assist in the management of metastatic breast, prostate, and colorectal cancers, CELLSEARCH stands out as a critical tool in cancer care. Although not specifically cleared to guide individual treatment decisions, the clinical insights derived from studies like PACE indicate a promising direction for personalized medicine in oncology.

For comprehensive information about CELLSEARCH’s intended use and limitations, including regulatory details, please refer to its official documentation.

Conclusion

The findings from the PACE trial mark a significant advance in the use of CTC enumeration as a biomarker for guiding treatment decisions in metastatic breast cancer, emphasizing the importance of tailored approaches to patient management in oncology. Menarini Silicon Biosystems continues its commitment to supporting healthcare providers in optimizing treatment strategies to enhance patient outcomes.