The Percentage of Anaplastic Lymphoma Kinase-Positive Tumor Cells Has Clinical Implications for Patients with Non-Small Cell Lung Cancer

Objectives: Anaplastic lymphoma kinase (ALK) is one of the leading therapeutic targets in patients with non-small cell lung cancer (NSCLC). However, the clinical importance that the percentage of ALK-positive tumor cells has on NSCLC remains unclear. Methods: A total of 344 ALK-positive patients were enrolled in this study. The percentage of ALK-positive tumor cells was identified by fluorescence in situ hybridization. The discrimination and calibration analyses of the nomogram were estimated with Harrell's C-index. Results: Higher percentages (≥50%) of ALK-positive tumor cells were significantly correlated with male gender, poor differentiation, and normal levels of carbohydrate antigen 153 (CA153) and blood platelets (p < 0.05). A shorter first-line progression-free survival (PFS) was correlated with a lower percentage (15-49%) of ALK-positive tumor cells, chemotherapy, a poor performance state, non-adenocarcinoma, as well as abnormal CA153 and Cyfra21-1 levels; and an abnormal thrombin time (p < 0.05). A low percentage of ALK-positive tumor cells, crizotinib treatment, CA153 levels, and neutrophil count were independent risk factors for poor PFS in the multivariate analysis (p < 0.05). The nomogram showed a C-index of 0.76 for first-line PFS. Conclusion: A nomogram including the percentage of ALK-positive tumor cells may act as a crucial indicator for first-line PFS in ALK-positive NSCLC patients.