Lung immune prognostic index as a prognostic factor in patients with small cell lung cancer

BACKGROUND: The lung immune prognostic index (LIPI) is a marker that combines the derived neutrophil‐to‐lymphocyte ratio (dNLR) and serum lactate dehydrogenase (LDH) level and is a recently reported prognostic factor of immune checkpoint inhibitor therapy for non‐small cell lung cancer (NSCLC). However, there are no reports regarding the prognostic value of LIPI in small cell lung cancer (SCLC). METHODS: We retrospectively enrolled 171 patients diagnosed with SCLC and treated at Shinshu University School of Medicine between January 2003 and November 2019. Progression‐free survival (PFS) and overall survival (OS) were compared according to LIPI, and we investigated whether LIPI could be a prognostic factor in SCLC using the Kaplan‐Meier method and univariate and multivariate Cox models. RESULTS: The median OS of the LIPI 0 group was significantly longer than that of the LIPI 1 plus 2 group (21.0 vs. 11.6 months, P < 0.001). The multivariate analysis associated with OS indicated that LIPI 1 plus 2 was an independent unfavorable prognostic factor in addition to poor performance status (2–3), old age (≥ 75 years) and stage (extensive disease [ED]). However, PFS of the LIPI 0 group was not significantly different from that of the LIPI 1 plus 2 group. In ED‐SCLC patients, the median PFS and OS of the LIPI 0 group were significantly longer than those of the LIPI 2 group (6.6 vs. 4.0 months, P = 0.006 and 17.1 vs. 5.9 months, P < 0.001, respectively). CONCLUSIONS: We confirmed the prognostic value of LIPI in SCLC, especially ED‐SCLC. KEY POINTS: Significant findings of the study: The present study is the first to demonstrate that pretreatment lung immune prognostic index is an independent prognostic factor associated with overall survival for small cell lung cancer. What this study adds: The utility of the lung immune prognostic index as a prognostic factor for small cell lung cancer.