Feasibility of cytological specimens for ALK fusion detection in patients with advanced NSCLC using the method of RT-PCR

Objectives: Histological tissues are preferred for anaplastic lymphoma kinase (ALK) fusion detection in non-small cell lung cancer (NSCLC). The aim of this study was to evaluate the feasibility of cytological sample as an alternative specimen for ALK fusion testing in patients with advanced NSCLC. Materials and methods: Advanced NSCLC patients with cytological specimens or tumor tissue who had their ALK fusion status detected by the method of reverse transcriptase polymerase chain reaction (RT-PCR) in Shanghai Pulmonary Hospital, Tongji University were included into this study. The efficacy was evaluated in those with ALK fusion positive and received the therapy of crizotinib. Results: 1274 patients were included in this study. Among them, 108 patients were ALK RT-PCR positive and 69 of them received crizotinib treatment. Among 1002 patients with cytological specimens, the average concentration of RNA extracted from cytological specimens was 60.99 ng/μl (95% confidence interval [CI], 55.56-66.60) and the incidence rate of ALK fusion was 8.3% (83/1002), which were similar to 63.16 ng/μl (95% CI, 51.88-76.34) (p = 0.727) and 9.2% (25/272, p = 0.624) in 272 patients with tumor tissue. Also, there were no statistically significant differences regarding to the objective response rate (ORR) (62.0% vs. 42.1%, p = 0.177) and the median progression free survival (mPFS) [8.6 months (95% CI 7.30-9.84) vs. 7.0 months (95% CI 4.54-9.47), p = 0.736] in patients of cytological group and tissue group after the treatment of crizotinib. Conclusion: Cytological specimens showed a high feasibility to detect ALK fusion status, which could be regarded as alternative samples for ALK fusion detection by the method of RT-PCR in patients with advanced NSCLC.