BACKGROUND: Increases in tumor marker concentrations usually suggest disease progression.

CASE REPORT: We here describe on 3 patients with non-small cell lung cancer whose serum concentrations of CYFRA21-1 increased in spite of successful treatment with crizotinib. Discontinuation of crizotinib resulted in a rapid decrease in serum CYFRA21-1 concentrations in all cases. In 1 patient with progressive disease, in spite of increasing the dose of crizotinib, CYFRA21-1 concentrations decreased.

CONCLUSIONS: Crizotinib can induce increases in CYFRA21-1 concentration without disease progression. Pulmonologists and oncologists should be aware of this novel phenomenon, and focus on interpretation of CYFRA21-1 concentrations in monitoring tumor response to crizotinib treatment.

Keywords: Carcinoma, Non-Small-Cell Lung - drug therapy, Antigens, Neoplasm - blood, Follow-Up Studies, Keratin-19 - blood, Lung Neoplasms - drug therapy, Protein Kinase Inhibitors - therapeutic use, Pyrazoles - therapeutic use, Pyridines - therapeutic use, Tomography, X-Ray Computed, Tumor Markers, Biological - blood