Comprehensive tumor-agnostic evaluation of genomic and epigenomic-based approaches for the identification of circulating tumor DNA in early-stage breast cancer.

BACKGROUND

The detection of circulating tumor DNA (ctDNA) after curative-intent therapy, referred to as molecular/minimal residual disease (MRD), is prognostic of disease recurrence in early-stage breast cancer (EBC). Tumor-agnostic approaches that rely on mutation-based assessment in fixed panels of common cancer driver genes have shown limited utility for detecting MRD in EBC. Methylation-based MRD (mMRD) may overcome the limitations of genomic-based MRD (gMRD), though limited clinical validation is available.

MATERIALS AND METHODS

To investigate this, we analyzed 290 longitudinally banked plasma samples from 95 participants diagnosed with early-stage estrogen receptor (ER)-positive/human epidermal growth factor receptor 2-negative (ER-positive) and triple-negative breast cancer (TNBC) undergoing neoadjuvant chemotherapy using a high-sensitivity genomic and epigenomic-based, tumor-agnostic ctDNA platform.

RESULTS

The baseline (pre-chemotherapy) ctDNA detection (mMRD) rate was 72.5% (66/91) across all participants (ER-positive: 33/48, 69%; TNBC: 33/43, 77%). Baseline ctDNA detection (mMRD) was associated with a higher risk of recurrence [hazard ratio (HR) 9.4, 95% confidence interval (CI) 1.3-70.3, P = 0.03]. Detection of ctDNA (mMRD) in the post-operative and follow-up periods were prognostic of worse event-free survival (EFS) (HR 17.0, 95% CI 6.0-48.0, P < 0.0001) with 62.5% sensitivity and 100% specificity for recurrence (positive predictive value 100%). The median lead time from mMRD detection to clinical recurrence was 152 days (range 15-748 days). gMRD, derived from plasma-only panel-based next-generation sequencing, was evaluated in all matched time points; the prognostic value was limited by clonal hematopoiesis of indeterminate potential, including pathogenic mutations in common cancer driver genes. Despite refinements in gMRD analysis, it remained inferior to mMRD. A combination of mMRD and gMRD did not outperform mMRD alone.

CONCLUSION

These results support further development of tumor-agnostic mMRD assays for the detection of ctDNA and assessment of these assays to develop clinical utility in this setting.