Validation of the lung immune prognostic index in extensive-stage small cell lung cancer: Post hoc analysis of the caspian and IMpower133 phase 3 trials.
BACKGROUND: The Lung Immune Prognostic Index (LIPI) is an inflammation-based biomarker associated with outcomes to immunotherapy across several tumor types. Its prognostic value in extensive-stage small-cell lung cancer (ES-SCLC), however, remains insufficiently validated. We aimed to validate the prognostic impact of LIPI in ES-SCLC using data from two phase III trials. METHODS: Patients enrolled in the CASPIAN (NCT03043872) and IMpower133 (NCT02763579) trials were included. LIPI groups were defined as good (dNLR<3 and LDH<ULN), intermediate (dNLR≥3 or LDH≥ULN) and poor (dNLR≥3 and LDH≥ULN). Overall survival (OS) and progression-free survival (PFS) were assessed across LIPI categories and treatment arms. RESULTS: LIPI was available for 1140 patients (Good: 34%, Intermediate: 49%, Poor: 17%), including 708 treated with chemotherapy-immunotherapy and 432 with chemotherapy alone. Poor LIPI was associated with unfavorable characteristics, including lower albumin levels and higher rate of liver metastases. Median OS was 14.6 months (95%CI: 12.4-15.9) for LIPI Good, 10.9 (10.1-11.5) for Intermediate, and 8.4 (7.1-9.3) for Poor (p < 0.0001). In multivariate models adjusted on gender, age, ECOG, treatment arm and metastatic sites, LIPI remained an independent prognostic factor for OS (HR Poor vs. Good: 1.76, 95%CI: 1.45-2.15, p < 0.001) and PFS (HR: 1.59, 95%CI: 1.33-1.90, p < 0.001). Although patients with poor LIPI derived limited benefit from immunotherapy, no significant treatment-LIPI interaction was observed. CONCLUSION: This large post hoc analysis confirms LIPI as a robust and clinically applicable prognostic biomarker in ES-SCLC. Patients with poor LIPI have substantially worse outcomes and limited benefit from immunotherapy, highlighting the need for novel therapeutic strategies in this subgroup.