Prevalence of KRAS Mutations in EGFR, ALK, and ROS1-negative Nonsmall-cell Lung Cancer: A Single-center Study

Background: Non-small-cell lung cancer (NSCLC) is the most common type of lung cancer and remains a major contributor to cancer-related mortality globally. The Kirsten rat sarcoma viral oncogene homolog ( KRAS ) oncogene is among the most frequently mutated genes in NSCLC, with significant implications for targeted therapy, including KRAS G12C inhibitors. However, data on KRAS mutation prevalence among Indian patients remain limited. Materials and Methods: In this retrospective study, we analyzed 93 biopsy-confirmed NSCLC cases from January 2020 to December 2021 that were negative for epidermal growth factor receptor ( EGFR ), anaplastic lymphoma kinase ( ALK ), and c-ros oncogene 1 ( ROS1 ) alterations. KRAS mutation testing was performed using Sanger sequencing. To support rapid mutation detection, we also designed an in-house drop-off droplet digital polymerase chain reaction (ddPCR) assay targeting codons 12, 13, and 61, and validated it in a randomly selected subset of 30 cases. Results: Sanger sequencing identified KRAS mutations in 26 of 93 cases (28%), predominantly in exon 2 (25%) and to a lesser extent in exon 3 (3%). While G12C (57%), G12D (30%), and G12V (9%) were the most frequently observed variants, the Q61H variant was the only variant in exon 3. The drop-off ddPCR assay showed 100% sensitivity, specificity, and concordance with Sanger sequencing. Conclusion: These findings highlight a substantial burden of KRAS mutations, particularly the G12C variant, among EGFR, ALK , and ROS1 -negative NSCLC cases in the Indian population. This study also demonstrates the reliability and clinical utility of a cost-effective, in-house ddPCR assay for KRAS mutation screening.