Clonal Hematopoiesis in Lung Cancer and Its Impact on Liquid Biopsy Based on Targeted Deep Sequencing

Background: Blood based liquid biopsy has proved its potential in enormous clinical applications, such as cancer screening, diagnosis, treatment guidance, disease tracking and monitoring. In certain scenario (e.g., molecular residual disease), it requires the technique to be able to detect mutation with very low frequency (0.001% ~ 1%). The major hurdle of ultra-sensitive circulating tumor DNA sequencing is the high background noise of plasma cell-free DNA (cfDNA) and clonal hematopoiesis (CH). Here in this study, we investigated the prevalence of CH in lung cancer patients and its interference with liquid biopsy. Methods: We retrospectively analyzed cfDNA and blood cell genomic DNA (gDNA) sequencing data sets (n=1261) from a group of Chinese lung cancer patients. Threshold (1%) and subthreshold (0.2%) for variant allele frequency were set and compared. We focused on 23 clonal hematopoiesis genes that were selected based on previous publications. Results: CH mutations were detected in 27.68% of all the patients at the threshold and 62.01% at the subthreshold, and the detection rate increased with age. DNMT3A was the most frequently mutated CH gene, accounted for more than half of the CH mutations. The CH mutations had a higher detection rate in smokers (72%) than non-smokers (59.4%) at subthreshold. VAFs of CH mutations in cell-free DNA strongly correlated with their VAFs in gDNA (Pearson’s R =0.92, p<2.2x10-16), while tumor derived somatic mutations didn’t have such correlation. Conclusion: Our study showed that clonal hematopoiesis is very common in lung cancer patients, especially when examining low frequency mutations. Sequencing of gDNA at equivalent depth is very important to filter out CH mutation in cancer liquid biopsy.