LAUSR

ALK FISH assay guides clinical decision to initiate therapy with ALK inhibitors in patients with stage IV non-small cells lung cancer (NSCLC). In this single institution retrospective study, we investigated the association between the strength of ALK positivity and progression-free survival (PFS) We screened 4,829 patients tested for ALK rearrangement by FISH from 01/06/2012 to 06/30/2018 and included 66 stage IV NSCLC ALK positive patients, who were ALK inhibitor naïve, received an ALK inhibitor, and been followed at least 10 months to the study. The median PFS for cases high positive cases [≥=50% positive nuclei; n = 49] and low positive cases [16-49% positive nuclei; n = 17] is 16 months and 4 months respectively, and the hazard ratio is 2.89 [95 CI 1.34-6.2] (p = 0.0068). When cases are stratified according to cut-off ≥=30% positive nuclei, the median PFS for cases above (n = 55) and below the cut-off (n = 11) is 12 and 3 months, respectively and the hazard ratio is 9.60 [95 CI 2.63-35.04] (p < 0.0001) Patients with low FISH positive results have shorter PFS. Although a biological reason is plausible, false positivity may be a contributing factor. For low positive results, confirmation of the FISH result with an orthogonal technology is warranted.