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MRD as detected by a novel tumor-informed ctDNA assay helped identify patients with TNBC who were at higher risk for distant recurrence after surgery.
Minimal residual disease (MRD) status as detected by a tumor-informed circulating tumor DNA (ctDNA) assay was successfully used to identify patients with triple-negative breast cancer (TNBC) at a higher risk for distant recurrence following surgery and neoadjuvant therapy, according to data from a substudy of the phase 3 NSABP B-59/GBG 96-GeparDouze trial (NCT03281954) presented at the 2025 San Antonio Breast Cancer Symposium.1
The parent study of B-59/GBG 96-GeparDouze evaluated 1550 patients with TNBC who were randomly assigned to receive atezolizumab (Tecentriq) plus paclitaxel and carboplatin vs placebo plus paclitaxel and carboplatin.
The MRD substudy included 212 patients and the primary objective was to demonstrate the association between a positive ctDNA result showing MRD positivity at the post-surgery timepoint and distant recurrence-free interval (DRFI).
At baseline, before initiation of neoadjuvant treatment, 96% of patients were ctDNA-positive. After completion of neoadjuvant treatment, ctDNA was 9%; after surgery, only 6% of patients were ctDNA-positive.
“In patients who did not achieve pathological complete response (pCR), 21% of patients remained ctDNA positive, whereas in the pCR group, 2% of patients remained ctDNA positive,” lead author Marija Balic, MD, PhD, said during a presentation of the data. Balic is a hematologic oncologist at the UPMC Hillman Cancer Center in Pittsburgh, Pennsylvania.
Primary analysis of DRFI by MRD status post-surgery revealed that 5% (7 out of 138) of patients who were MRD-negative developed recurrence. In patients who were MRD-positive, 78% (7 out of 9) patients developed recurrence (HR = 30.3; 95% CI, 10.4-88.7; P < .0001).
Further analysis revealed that patients who were ctDNA-negative with no pCR had a 12% chance of recurrence and patients who were ctDNA negative with pCR had a 2% chance of recurrence. For patients who were ctDNA positive, the risk of recurrence was 87% with no pCR and 50% with pCR.
The trial evaluated neoadjuvant atezolizumab with neoadjuvant anthracycline- and taxane-based combination chemotherapy followed by adjuvant atezolizumab in patients with TNBC.
Patients were stratified by region, tumor size, nodal status, and whether they received doxorubicin or epirubicin. Following stratification, patients randomly received either atezolizumab (1200 mg every 3 weeks) or placebo concurrently with neoadjuvant chemotherapy.
Following surgery, patients resumed their assigned study agent. Adjuvant radiotherapy was coadministered with the study agent during this period. At 12 and 24 months post randomization, survival follow-up was carried out. The median follow-up post-surgery was 37 months.
The mean age of the patients in the substudy was 50 years, 78.9% had high-grade tumors, 61.2% were node positive at presentation, and 51% received atezolizumab.
A total of 160 patients with baseline blood samples had sufficient DNA yield to perform whole exome sequencing (WES) for development of the bespoke assay for ctDNA.
The tumor-informed ctDNA assay determined variant discovery through WES of the primary tumor. To subtract the germline variants, sequencing of mononuclear cells was performed.
“Up to 200 somatic variants were identified for each individual patient. The median number of variants was 164.5 and ranged between 42 to 200,” Balic said.
For ctDNA detection, plasma samples were hybridized to bespoke patient-specific probe sets to detect somatic variants. In 98.4% of plasma samples, this sequencing was successfully performed to detect somatic variants. A proprietary algorithm was used to determine ctDNA detection.
“This substudy is one of the largest evaluations of a bespoke MRD assay in prospectively collected serial blood samples from patients with TNBC,” Balic said. “MRD-positive status was associated with a 30-fold higher risk of distant recurrence compared to patients who were MRD-negative and 95% of patients who were MRD-negative post-surgery remained free of disease at 3 years,” she concluded.
Disclosures: Balic disclosed financial relationships with Amgen, AstraZeneca, Daiichi Sankyo, Eli Lilly, Gilead, Menarini, MSD, Novartis, Pierre Fabre, Roche, Seagen, Stemline, and grant/research support from AstraZeneca, Daiichi Sankyo, Novartis, and Pfizer. Additional financial disclosures include travel grants from BMS, Daiichi Sankyo, MSD, Roche, Pierre Fabre.
Balic M, Tang G, Young, G, et al. Evaluation of a whole-exome sequencing tumor-informed circulating tumor DNA MRD assay in patients with early triple-negative breast cancer (TNBC) receiving neoadjuvant chemotherapy (NAC) with or without atezolizumab: A prospective sub study of the NSABP-B59/GBG-96-GeparDouze Trial. Presented at: San Antonio Breast Cancer Symposium; December 9-12, 2025; San Antonio, TX. Abstract RF4-03.
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