Circulating tumor cells may predict OS in metastatic breast cancer
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Circulating tumor cell assessments a month after treatment initiation predicted survival among patients with metastatic breast cancer, according to findings presented at the virtual San Antonio Breast Cancer Symposium.
Patients who demonstrated circulating tumor response achieved significantly longer OS, and early treatment monitoring appeared predictive for all tumor subtypes, results of the global pooled analysis showed.
“These results provide clinical validation of circulating tumor cell (CTC) monitoring as an early treatment response marker in advanced breast cancer and suggest the potential for clinical utility,” Wolfgang J. Janni, MD, PhD, professor and director of the women’s clinic at Ulm University in Germany, said during a presentation.
Conventional imaging typically is used to monitor response to breast cancer treatment; however, depending on disease subtype, it can take a few months to detect changes.
Janni and colleagues aimed to determine whether a simple test that detects CTCs shed into the bloodstream could predict treatment response and prognosis earlier.
Researchers screened peer-reviewed published studies with data on repeated circulating tumor assessments for patients with metastatic breast cancer, and asked investigators involved with these studies to provide individual patient data for the pooled analysis.
The analysis included records of 4,079 patients from 14 studies. All patients had baseline and follow-up assessments measured by the CellSearch test (Menarini Sillicon Biosystems). Median time between baseline and first follow-up assessments was 29 days (interquartile range, 26-54).
Janni and colleagues used log-rank tests and Cox regression to evaluate the association between CTC enumeration results and OS in the entire study population, as well as in predetermined subgroups.
Results showed 19.9% of patients were CTC-negative at baseline and at follow-up assessment (negative/negative); 7.5% were negative at baseline but converted to positive at follow-up assessment (negative/positive); 27.1% were positive at baseline but converted to negative at follow-up assessment (positive/negative); and 45.5% were positive at both baseline and follow-up assessments (positive/positive).
Researchers reported median OS of 47.05 months for patients in the negative/negative group. This was significantly longer than the median OS observed in the other three groups: 29.67 months (HR = 1.74; 95% CI, 1.43-2.1) for negative/positive, 32.2 months (HR = 1.52; 95% CI, 1.32-1.74) for positive/negative and 17.87 months (HR = 3.15; 95% CI, 2.78-3.57) for positive/positive.
Among all patients who were CTC-positive at baseline, those who converted to negative status at follow-up assessment achieved significantly longer OS (HR = 0.49; 95% CI, 0.44-0.54). This trend persisted when researchers assessed survival by subtype: luminal like (HR = 0.47; 95% CI, 0.41-0.54), HER2-positive (HR = 0.54; 95% CI, 0.42-0.69) and triple-negative (HR = 0.41; 95% CI, 0.32-0.52).
“This provides clear evidence of improved OS among CTC responders compared with CTC nonresponders,” Janni said.
The inclusion of individual patient data from around the world strengthened the study, Janni said. However, researchers acknowledged the study was limited by a lack of information about specific treatments many patients received. This prevented investigators from assessing whether the predictive potential of CTCs varied by treatment.
“With the increasing number of treatment options available to patients with metastatic breast cancer, being able to predict and monitor treatment responses rapidly will be critical to aiding treatment decisions,” Janni said in a press release. “These data indicate that CTC dynamics can predict the trajectory of the disease a little more than 4 weeks after initiating treatment. This provides an advantage over conventional imaging methods and can help physicians determine very early on whether a treatment should be continued.”
Perspective
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Carlos L. Arteaga, MD, FAACR
This is a very interesting presentation about the clinical utility of repeated CTC enumeration as an early treatment monitoring tool in metastatic breast cancer. This very large, pooled analysis really instructs us about a noninvasive approach that may provide an advantage over conventional imaging methods that can take up to 3 months before changes can be detected in breast tumor tissue.
UT Southwestern Medical Center
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Janni WJ, et al. Abstract GS4-08. Presented at: San Antonio Breast Cancer Symposium (virtual meeting); Dec. 8-11, 2020.
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