According to a retrospective study, monitoring the changes in circulating tumor cell (CTC) count can accurately predict the prognosis and survival. The study compared how well CTCs and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) predicted survival in MBC patients on standard therapies. The result showed that both technologies correlate to overall MBC patient survival (p
The CellSearch System is the first automated 510(k) diagnostic test to capture and detect CTCs. CTCs are tumor cells that have detached from solid tumors and entered the patient’s blood.
Measuring CTCs in metastatic breast cancer patients provides oncologists with an additional tool to help us better monitor patient outcomes, said one of the lead authors, Dr. Massimo Cristofanilli, associate professor in the Department of Breast Medical Oncology at The University of Texas M. D. Anderson Cancer Center. The CellSearch CTC test provides an early indication about patients’ disease progression and overall survival.
For patients with MBC, CTCs and FDG-PET/CT may prove to be the most promising new tools. The number of CTCs identified in patients with MBC is related to patient prognosis; a high number of CTCs at any time during treatment is associated with poor prognosis.
Veridex is committed to providing oncologists with high-value in vitro diagnostic solutions, such as the CellSearch CTC test, to help them make informed patient care decisions, said Ken Berlin, general manager of Veridex. This study demonstrates the utility of integrating the CellSearch CTC test in therapeutic monitoring of patients with metastatic disease.
A retrospective study was performed on 115 patients with MBC who had the CellSearch test performed as part of their initial staging process at M.D. Anderson over a three-year period. CTC count and FDG-PET/CT imaging were performed at baseline in 102 evaluable patients before starting a new therapy and then again at the midpoint of their therapies (9 – 12 weeks). Patients outcomes were categorized according to midtherapy CTC counts as favorable (< five CTCs/7.5 mL blood) or unfavorable (greater than or equal to five CTCs/7.5 mL blood). Based on FDG-PET/CT, patients were considered responders if metabolic activity of target lesions decreased more than 25% compared to baseline, and if there was no change or a decrease in size. Patients were considered nonresponders if the FDG uptake was similar or higher and/or if target lesions had increased in size. CTC counts and FDG-PET/CT response at midtherapy were compared, and univariate and multivariate analyses were performed to identify factors associated with survival.
The study involved a total of 115 patients with MBC and 102 were evaluable for efficacy. The median overall survival time was 14 months (range, 1 to > 41 months). In univariate analysis, both midtherapy CTC counts and FDG-PET/CT response predicted overall patient survival (p<.001 and p=.001, respectively). The overall concordance between the CTC counts at midtherapy and FDG-PET/CT was 67% for response/nonresponse and 74% for progression/nonprogression. In the discordant category, detection of five or more CTCs during therapeutic monitoring accurately predicted prognosis in MBC beyond metabolic response. FDG-PET/CT was able to predict outcome in discordant instances of patients with less than five CTCs at midtherapy. Midtherapy CTC levels remained significant in a multivariate analysis (p=.004). These results suggest a higher and independent predictive value of CTCs compared with FDG-PET/CT among patients with a CTC count of five or more. In addition, there was a strong correlation between complete response and the absence of significant levels of CTCs (median CTC level zero).
Dr. Cristofanilli is a principal investigator for a CellSearch validation study and received honoraria from Veridex, LLC.