Correlation analysis between skeletal muscle index evaluated by chest CT and peripheral blood nutrition/inflammation/immune indicators, as well as immune therapy efficacy in non-small cell lung cancer patients

Worldwide, non-small cell lung cancer (NSCLC) ranks first in both incidence and mortality. In recent years, breakthroughs have been made in immunotherapy represented by programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) inhibitors, which have significantly improved the prognosis of NSCLC patients. It is known that in various solid tumors, the patient’s skeletal muscle mass and nutritional/inflammatory/immune status may affect the efficacy of immunotherapy. However, in newly diagnosed NSCLC patients, it remains unclear whether skeletal muscle mass can be assessed by chest CT, and the relationship between skeletal muscle mass and patients’ nutritional/inflammatory/immune status, immunotherapy efficacy, and survival is also unknown. Therefore, this study aimed to explore the relationship between the skeletal muscle index (SMI) evaluated by chest CT and the nutritional/inflammatory/immune status, immunotherapy efficacy, and survival time of these patients through retrospective analysis. We included 159 newly diagnosed NSCLC patients who received first-line immunotherapy (monotherapy with PD-1/PD-L1 antibodies or combined chemotherapy regimens containing PD-1/PD-L1 antibodies) from January 2020 to September 2024. Based on chest CT images before the first treatment, their chest SMI was measured and converted using SliceOmatic software, and they were divided into a high SMI group and a low SMI group according to the 50% cutoff value. Then, indicators such as body weight, height, blood routine, albumin (ALB), and prealbumin (PALB) before the first treatment were collected, and further converted into nutritional/inflammatory/immune indicators including body mass index (BMI), neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and advanced lung cancer inflammation index (ALI). After receiving immunotherapy, the patients’ tumor treatment responses were evaluated and converted into objective response rate (ORR), and progression-free survival (PFS) was calculated. The correlation between SMI and the above nutritional/inflammatory/immune indicators and efficacy indicators was analyzed, and the differences in these indicators between the high SMI group and the low SMI group were compared. The results showed that among the 159 NSCLC patients receiving first-line immunotherapy, the chest SMI at initial diagnosis was 65.45±13.99, with 66.91±13.51 in males and 55.89±13.61 in females. No correlation was found between chest SMI and tumor efficacy indicators (ORR and PFS). However, chest SMI was negatively correlated with inflammatory/immune indicators such as NLR, PLR, SIRI, and SII, positively correlated with advanced lung cancer inflammation index (ALI), and also positively correlated with nutritional indicators such as BMI, hemoglobin (HB), and prealbumin (PALB). After dividing into the high SMI group and the low SMI group according to the 50% cutoff value, there was no significant difference in tumor efficacy indicators (ORR and PFS) between the two groups. Compared with the high SMI group, the low SMI group had significantly higher inflammatory/immune indicators (NLR, PLR, SIRI, SII, etc.), and significantly lower nutritional indicators such as BMI, HB, and PALB. Therefore, we conclude that among newly diagnosed NSCLC patients, those with low chest SMI have poorer nutritional status, higher inflammatory levels, and lower immune status. This suggests that the low nutritional status and high inflammatory status associated with reduced SMI already exist in some lung cancer patients at initial diagnosis, which may affect the efficacy of subsequent immunotherapy. Therefore, it is necessary to closely monitor patients’ SMI and the above-mentioned inflammatory/immune/nutritional indicators, and provide early intervention when necessary.