Utility of circulating plasma cell-free DNA for detection and quantification of brain arteriovenous malformations

Brain arteriovenous malformations (BAVMs) are primarily associated with somatic activating pathogenic KRAS variants. KRAS-targeting therapy is emerging as a potential treatment for BAVMs. However, current molecular diagnosis relies on surgically obtained tissue samples. Here, we investigated the feasibility of using cell-free DNA (cfDNA) from the blood for molecular diagnosis in sporadic BAVM patients. We included 31 BAVM patients and extracted genomic DNA from BAVM tissues, while paired cfDNA was isolated from plasma. Additionally, fifty plasma cfDNA samples from unaffected individuals served as controls. By utilizing droplet digital polymerase chain reaction (ddPCR), we tested KRAS c.35 G>A p.Gly12Asp (p.G12D) and c.35 G>T p.Gly12Val (p.G12V) variants in all samples. Among the 31 BAVM samples, KRAS somatic mutations were identified in 24 patients (77 %), comprising 79 % (19 out of 24) p.G12D and 21 % (5 out of 24) p.G12V variants. The variant frequencies (VFs) ranged from 0.227 % to 8.327 %, with positive droplets ranging from 17 to 1025. 63 % (15 out of 24) of patients with KRAS mutations had≥2 positive droplets in their cfDNA samples. In contrast, in none of the 50 control samples more than two positive droplets were detected. Specifically, 13 plasma samples (68 %) were positive for p.G12D mutation. The VFs in plasma cfDNA samples ranged from 0.042 % to 5.172 %. Furthermore, ddPCR demonstrated a sensitivity of 63 %, specificity of 100 %, positive predictive value of 100 %, and negative predictive value of 81 % for detecting plasma cfDNA. The VFs in mutant tissues had an inverse trend with the largest nidus sizes, volumes, and patient age, while an opposite trend was observed in plasma cfDNA. Taken together, we successfully detected pathogenic somatic activating KRAS variants in cfDNA obtained from the plasma of BAVM patients. The diagnostic utility of liquid biopsy for BAVMs will facilitate the development of personalized therapeutic approaches and offer opportunities for novel strategies to halt, slow, or delay disease progression.