Background/Objectives: Immune checkpoint inhibitors (ICIs) improve outcomes in metastatic non-squamous non-small cell lung cancer (NSCLC), yet predictive biomarkers remain limited. This study investigated whether CD34-stained microvessel density (MVD) is associated with ICI efficacy. Methods: Patients with metastatic non-squamous NSCLC and tumor specimen suitable for anti-CD34 immunohistochemistry were included. In the derivation cohort, ROC analysis for objective response rate (ORR; CR + PR) identified a Youden-optimized threshold of 14.5 vessels/HPF (×400) (sensitivity 67%, specificity 93%; AUC 0.744, 95% CI 0.53–0.95; p = 0.021), which was applied without re-optimization to an internal validation cohort and a chemotherapy-only comparator. Results: In the derivation cohort, (n = 25), ORR was higher with MVD ≥ 14.5 than <14.5 (88.9% vs. 25.0%; p = 0.004) and OS/TFST were longer (OS: 53.0 vs. 17.1 months, p = 0.037; TFST: 50.0 vs. 6.0 months, p = 0.014). In the validation cohort (n = 13), MVD ≥ 14.5 was associated with longer TFST (9.0 vs. 4.0 months; p = 0.035) and numerically longer OS (12.0 vs. 7.0 months; p = 0.059). As a cut-off-independent sensitivity analysis, continuous MVD (per five vessels/HPF) was associated with longer TFST (HR 0.663, 95% CI 0.454–0.969; p = 0.034). No association was observed in the chemotherapy-only cohort. Conclusions: Higher CD34-MVD may be a feasible vascular metric associated with ICI outcomes that warrants prospective validation.
Çerme et al. (Mon,) studied this question.