Variant allele frequency in circulating tumor DNA correlated with tumor disease burden and predicted outcomes in patients with advanced breast cancer.

ABSTRACT

PURPOSE: In patients with first-line advanced breast cancer (ABC), the correlation between ctDNA variant allele frequency (VAF) and tumor disease burden, and its prognostic value remains poorly investigated. METHODS: This study included patients with ABC diagnosed at Peking University Cancer Hospital who performed ctDNA test before receiving first-line treatment. Baseline plasma samples were collected for assessing ctDNA alterations and VAF with next-generation sequencing. The sum of tumor target lesion diameters (SLD) was measured with imaging methods according to RECIST 1.1 criteria. RESULTS: The final cohort included 184 patients. The median age of the cohort was 49.4 (IQR 42.3-56.8) years. The median VAF was 15.6% (IQR 5.4%-33.7%). VAF showed positive correlation with SLD in patients with relatively large tumor lesions (r = 0.314, p = 0.003), but not in patients with small tumor lesions (p = 0.226). VAF was associated with multiple metastasis sites (p = 0.001). Multivariate Cox regression analysis showed that high VAF was associated with shorter overall survival (OS) (HR 3.519, 95% confidence interval (CI) 2.149-5.761), and first-line progression-free survival (PFS) (HR 2.352, 95%CI 1.462-3.782). Combined VAF and SLD improved prediction performance, both median OS and PFS of patients in VAF(H)/SLD(H) group were significantly longer than VAF(L)/SLD(L) group (mOS 49.3 vs. 174.1 months; mPFS 9.6 vs. 25.3 months). CONCLUSION: ctDNA VAF associated with tumor disease burden, and was a prognostic factor for patients with ABC. A combination of ctDNA test and radiographic imaging might enhance tumor burden evaluation, and improve prognosis stratification in patients with ABC.