Serum ferritin level is an effective prognostic factor for lung cancer immunotherapy.

Immunotherapy of lung cancer has achieved promising clinical results. However, it is urgent to develop predictive biomarkers for effective immunotherapy. While ferroptosis plays a critical role in immunotherapy efficacy, ferritin is an important regulatory factor. We, therefore, hypothesize that basal serum ferritin levels before immunotherapy and their corresponding changes during immunotherapy can be useful predictors of immunotherapy response in patients with lung cancer. We measured serum ferritin levels in 107 patients with lung cancer before and during immune checkpoint blockade treatments and studied the correlation between ferritin levels, response rate, and survival. Moreover, the correlation between basal ferritin and PD-L1 expression, tumor stages and pathological types was also analyzed. Patients with lower basal serum ferritin levels before immunotherapy had longer progression-free survival (PFS) (median 7 vs 4 months, P = .023) and higher disease control rate (DCR) (X² = 4.837, P = .028), those with downregulated serum ferritin levels during immunotherapy correlated with longer PFS (median 9.5 vs 4 months, P < .001) and higher DCR (X² = 6.475, P = .011). However, the "integrated factor", which was calculated as the combination of lower basal serum ferritin levels before immunotherapy and downregulated serum ferritin levels during immunotherapy, correlated with prolonged PFS (P < .001). Multivariate analyses revealed that the basal serum ferritin levels before immunotherapy and the corresponding changes during immunotherapy were both strong independent prognostic factors (hazard ratio (HR) = 1.60, P = .041; HR = 2.65, P = .001). These findings suggest that serum ferritin levels can be used as a prognostic biomarker for lung cancer in predicting immunotherapy efficacy.