Single-center retrospective study of prognostic value of variant allele frequency in ctDNA in patients with advanced breast cancer

In patients with first-line advanced breast cancer (aBC), the correlation between circulating tumor DNA (ctDNA) variant allele frequency (VAF) and tumor disease burden, and its prognostic value is unclear. A retrospective study at Peking University Cancer Hospital (Beijing, China) included aBC patients who underwent ctDNA VAF testing before initiation of treatment. The median VAF was 15.6% (IQR 5.4-33.7). VAF showed positive correlation with the sum of tumor target lesion diameter (SLD) among patients with relatively large tumor lesions (r=0.314; p=0.003) but not among patients with small tumor lesions (p=0.226). The figure shows that high VAF was associated with shorter overall survival (HR 3.519; 95% CI 2.149-5.761) and first-line progression-free survival (2.352; 1.462-3.782). Combination of VAF and SLD improved prediction performance. The authors conclude that among patients with first-line aBC, baseline VAF in ctDNA was associated with disease burden, and was a prognostic factor.