Brief Report: Impact of reflex testing on tissue-based molecular genotyping in patients with advanced non-squamous non-small cell lung cancer

Introduction/Background DNA-based molecular genotyping is an essential component of management of patients with metastatic non-squamous non-small cell lung cancer upon initial diagnosis. We hypothesized that implementation of a reflex testing pathway initiated by pathologists would ease logistical barriers and challenges in ordering tissue-based DNA-based molecular genotyping. Materials and Methods We conducted a retrospective cohort study at the University of Pennsylvania. Eligible patients had a histological or cytological diagnosis of metastatic non-squamous non-small cell lung cancer between 2015-2019. Patients were divided into 2 cohorts: prior to initiation of reflex testing pathway (2015-2016) and post-initiation of the reflex testing pathway (2017-2019). Two-tailed Z test was used to compare proportions (alpha=0.05) pre- and post-reflex implementation. Results Between 01/01/2015, and 12/31/2019, 529 DNA tissue-based molecular tests were included, 172 pre-initiation of reflex testing and 357 post-initiation of the reflex pathway. The proportion of completed DNA tissue-based tests per patient increased after implementation of the reflex pathway, 42% (172 tests/410 patients) to 58% (357 tests/617 patients) (p<0.001). Post implementation of the reflex pathway, the proportion of cytology specimens utilized for molecular testing increased from 43/172 (25%) to 194/357 (54%) (p<0.001). Median turnaround time for DNA tissue-based molecular genotyping results was shorter for liquid cytology vs. fixed tissue specimens (median 24 vs. 27 days, p=0.003). Conclusions In a single institution, implementation of a reflex pathway increased the proportion of patients with successful DNA tissue-based molecular testing. Our study demonstrates that utilization of reflex testing pathways can be adopted to remove barriers in tissue-based comprehensive molecular genotyping.