Posted: Thursday, February 10, 2022
A study presented at the 2021 San Antonio Breast Cancer Symposium (SABCS) assessed whether circulating tumor DNA (ctDNA) in patients who completed treatment for early-stage triple negative breast cancer could be used to guide future therapy for these patients. Nicholas Turner, MD, PhD, of the Institute of Cancer Research in London, United Kingdom, presented these data from the c-TRAK TN trial on behalf of his colleagues (Abstract GS3-06).
This trial enrolled 208 patents with early-stage triple-negative breast cancer who had either residual disease after neoadjuvant chemotherapy, a tumor size greater than 20 mm, and/or axillary lymph node involvement if adjuvant chemotherapy was administered. Researchers sequenced tumor tissue to identify somatic mutations that might be used for tracking via personalized digital polymerase chain reaction ctDNA assays. Patients underwent blood sample testing every 3 to 12 months. If ctDNA was detected, patients were randomly assigned 2:1 to receive either 200 mg of intravenous pembrolizumab every 3 weeks for 1 year or observation. The observation arm closed in June 2020, and all patients who had positive ctDNA were given pembrolizumab.
Among the enrolled patients, 171 had trackable mutations, and 161 underwent ctDNA surveillance. ctDNA was detected 12 months from the start of surveillance at a rate of 27.3% (44 of 161 patients). ctDNA positivity rates at baseline, 3, 6, 9, and 12 months were 14.3%, 5.2%, 5.2%, 8.3%, and 2.4%, respectively.
There were 45 patients who entered the therapeutic component of the trial; 31 were assigned to receive pembrolizumab and 14 were assigned to observation. Of the patients who were allocated to pembrolizumab, 72% had metastatic disease at the time of ctDNA detection on staging scans. Five patients actually started on pembrolizumab; at the time of data analysis, none had achieved sustained clearance of ctDNA, and four experienced recurrence. The median time to recurrence was 4.1 months among those who underwent observation.
Disclosure: For a full list of authors’ disclosures, visit abstractsonline.com.