Research presented at the San Antonio Breast Cancer Symposium highlighted the successful use of the Parsortix PC1 Clinical System for circulating tumor cell (CTC) enrichment in blood from patients with metastatic breast cancer, allowing for a variety of possible downstream analyses.
In this exclusive MedPage Today video, co-author Julie Lang, MD, chief of breast surgery at the Cleveland Clinic in Ohio, discusses the findings of the multicenter study.
Following is a transcript of her remarks:
So our investigative team set out to perform a multicenter clinical study on circulating tumor cells and metastatic breast cancer. We used the Parsortix PC1 System, which is made by the company ANGLE Parsortix, to evaluate metastatic breast cancer patients compared to healthy volunteers for the presence of circulating tumor cells. We enumerated or counted circulating tumor cells, and we also studied multiple downstream analysis tools to look at circulating tumor cells and their tumor biology.
The study included a patient population of 216 patients with metastatic breast cancer, and these patients were either newly diagnosed or had progressive metastatic disease. So these patients were all required to be initiating a new therapy, and we required a minimum of 7 days between cytotoxic therapy and drawing blood for the Parsortix study. Patients also received endocrine therapy or immunotherapy as per their treating physician.
We also included 206 healthy volunteers in this study. And the primary endpoint was looking at cytology of the circulating tumor cells to identify these circulating tumor cells from the blood. The other downstream analyses that we looked at were quantitative real-time PCR, RNA sequencing, and HER2 by FISH, or fluorescence in situ hybridization.
And so in the study what we found is that we were able to detect circulating tumor cells from the metastatic breast cancer patients. And in fact what we found is that 56.8% of metastatic breast cancer patients had greater than or equal to one circulating tumor cell, 28% of metastatic breast cancer patients had greater than or equal to five circulating tumor cells. And by combining gene expression with circulating tumor cell accounting or enumeration, we could increase the number of patients, increasing sensitivity, for the detection of circulating tumor cells.
Interestingly, patients with progressive disease had higher rates of detection of circulating tumor cells, and in fact progression was found in 88.6% of patients who had an indwelling port-a-cath present. And so this is a patient population likely to benefit from using liquid biopsy to detect circulating tumor cells. We found that when we looked at cancer cell lines spiked into blood in order to establish the baseline characteristics of the assay performance, 37% to 57% of cancer cell lines spiked into blood and processed through Parsortix were lost due to the cytology processing when making slides. And so this impacts the study results by decreasing the sensitivity. So further refinements to the cytology processing methods would be very helpful, and then we would be able to detect circulating tumor cells from increased numbers of metastatic breast cancer patients. This data may be very helpful as we move towards an era of precision medicine.
So CTCs as a liquid biopsy tool could be useful to help select targeted therapies or to determine the tumor burden of a metastatic patient and to monitor their response to treatment and detect if the treatment is working, or if the treatment is not benefiting the patients. This could be used to decide to go along a new therapeutic line of treatment for the patient.
So this was the first-ever FDA clearance of a product for harvesting cancer cells from the blood of breast cancer patients for subsequent downstream analysis. So we’re very excited by this study and the results, but further directions would include these subsequent downstream analyses and improving cytology to ensure that we have improved sensitivity for the detection of circulating tumor cells. Further refinements in gene expression analysis of rare mixed cell populations such as circulating tumor cells would be very helpful in order to be precise in terms of the readout of gene expression for these patients. Sequencing studies to look at mutations present in the circulating tumor cells could also be very useful.
And so we’re very excited about future studies applying the ANGLE Parsortix, now FDA approved, in combination with other assays so that this could be studied in the context of clinical trials and ultimately could be incorporated by oncologists in the treatment of breast cancer patients in the future.