STING1 and small cell lung carcinoma: To address this gap, we developed the DDR-Immune Fitness (DDR-IF) score-a composite biomarker that integrates measures of genomic instability (homologous recombination deficiency [HRD] and tumor mutational burden [TMB]) with immune contexture (STING pathway activation), derived from single-cell multi-omics data of 82 SCLC tumors (1, 3).