Frequency of T790M mutations after progression on epidermal growth factor receptor tyrosine kinase inhibitor in metastatic non-small cell lung cancer in Indian patients: real-time data from tertiary cancer hospital

Aim: The aim of this study is to determine the incidence of T790Mmutations after progression on epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) and median duration on TKI before progression on TKI. Methods: Records of Rajiv Gandhi Cancer Institute and Research Centre, of patients who were diagnosed with metastatic adenocarcinomaof the lungand progressed on oral EGFR TKIs and underwent T790Mmutation analysis in the last 6 months were retrospectively reviewed. The incidence of T790Mpositivity, sites of progression, and median duration of TKI treatment before progression was calculated. Results: Among 31 patients, 10 patients have undergone rebiopsy, and 24 patients had undergone liquid biopsyby Droplet Digital polymerase chain reaction(ddPCR), and three patients had undergone both tests. Among all, the rate of T790Mpositivity was 54.8%. Among these 17 patients positive for T790M, seven patients were positive by biopsy, and 11 patients were positive by ddPCR. Among three patients who underwent both, one was positive by both. The most common site of progression among all patients is pleura, and 10% of patients progressed in brain post-TKI. Median progression-free survival on TKI before progression is 289.7 days, highest being 1290 days, and lowest 45 days. Conclusions: Exact incidence of T790Mmutations after progression on TKI s in Asian population is not exactly known and requires large data, as incidence may be different than reported in the Western population. Rebiopsy and ddPCR help to determine the most common type of resistance after progression on TKI, for which effective targeted therapy is available.