Prognostic and predictive impact of creatine kinase level in non-small cell lung cancer treated with tyrosine kinase inhibitors

BACKGROUND: The use of tyrosine kinase inhibitors (TKIs) is associated with incident creatine kinase (CK) elevation in the treatment of advanced non-small cell lung cancer (NSCLC) patients. However, whether higher CK levels are associated with better antitumor responses or survival remains to be explored. We intend to investigate the clinical correlation between CK levels and TKI efficacy in advanced NSCLC. METHODS: In this retrospective study, we enrolled 135 patients with stage IV NSCLC receiving TKI-based therapy in our center between June 2012 to July 2020. CK levels were monitored from the initiation of TKI medication and during the administration period. An X-tile analysis provided the optimal cutoff point for higher baseline CK. Patients were identified and grouped according to their baseline CK level and fold changes during TKI therapy. The primary endpoints included progression-free survival (PFS) and overall survival (OS), and the objective response rate (ORR) was calculated as the secondary endpoint. RESULTS: Among the 135 patients included in our study, those with higher baseline CK levels (≥70 U/L) had favorable PFS (15.2 vs. 8.8 months; P=0.028), while patients with significantly elevated CK (the highest CK value/baseline CK value ≥2 times) appeared to gain better PFS (14.6 vs. 10.0 months; P=0.139). The overall ORR was 67.4%. Patients with higher baseline CK levels had numerically higher ORR (74.6% vs. 60.3%; P=0.076). Similarly, patients with significant CK elevation had a superior 4-month PFS rate (77.6% vs. 59.7%; P=0.029). Results from the subgroup analyses were identical to the overall ones. For patients with higher baseline CK levels, those experiencing significant CK elevation had prolonged PFS (17.2 vs. 14.2 months; P=0.038); a same trend was obtained from the lower baseline CK group (<70 U/L) (9.4 vs. 7.9 months; P=0.038). In multivariable analysis, higher baseline CK level and significant CK elevation remained statistically associated with PFS, with hazard ratios of 0.48 and 0.59, respectively. CONCLUSIONS: Both higher baseline CK levels and significant CK elevation after treatment were correlated with prolonged PFS in NSCLC treated with TKIs, suggesting the potential prognostic and predictive impact of CK level on these patients.