medwireNews: The presence of circulating tumour cells (CTCs) 5 years after the treatment of high-risk, hormone receptor (HR)-positive breast cancer is prognostic for late disease recurrence, research demonstrates.
This secondary analysis was conducted among 547 trial participants with lymph node-positive or high-risk lymph node-negative, stage II–III, HER2-negative breast cancer who had CTCs measured 5 years after surgery and adjuvant chemotherapy, at which point they were free from clinical recurrence.
Overall, 5.1% of the 353 patients with HR-positive disease tested positive for CTC s, defined as at least one CTC per 7.5 mL of peripheral blood, while 6.5% went on to develop recurrent disease a median of 2.8 years after the test.
The recurrence rate among the CTC-positive patients was 21.4% per person-year of follow-up, at seven recurrences per 32.7 person–years, whereas the rate for their CTC-negative counterparts was 2.0% per person-year of follow-up and 16 recurrences per 796.3 person–years.
On further examination, the rate of recurrence was 4.8% for zero cells per 7.5 mL, rising to 16.7% for a CTC count of one and 83.3% for those with a count of two or more per 7.5 mL, suggesting that “a numerically higher recurrence risk is associated with higher CTC burden”, the researchers comment in JAMA Oncology.
And a positive CTC assay was associated with a 13.1-fold higher risk for recurrence than a negative result in the HR-positive patients, after adjusting for factors including age, tumour size, lymph node status and disease grade.
The rate of CTC-positive assays was similar among the 193 HR-negative patients and their HR-positive counterparts, at 4.1%. But after a median of 2.8 years of follow-up, just one (0.5%) CTC-negative patient in the HR-negative subgroup had relapsed, suggesting that CTC status was “not associated with late recurrence” in these patients, the researchers remark.
Lead investigator Joseph Sparano, from the Albert Einstein College of Medicine in New York, USA, and co-workers say their findings “provide proof of concept supporting further blood-based biomarker tests such as the CTC assay for early detection of late clinical recurrence and for identifying subjects at low risk of late recurrence.”
Nevertheless, they caution that “further evaluation is required to confirm the clinical validity and determine the clinical utility of performing the CTC assay in this context.”
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