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The aim of this study was to investigate whether a tumor microenvironment, abundant in microvessels, affects epidermal growth factor receptor–tyrosine kinase inhibitor (EGFR-TKI) efficacy in patients with non-small cell lung cancer (NSCLC) and EGFR mutations. We retrospectively studied the data of 40 post-operative patients with recurrent NSCLC and EGFRmutations who received EGFR-TKIs as a first-line treatment at Kumamoto University Hospital between January 2010 and February 2021. Tumor sections were retrieved from the tissue registry and analyzed for CD34-positive microvessels using immunohistochemical techniques. The microvascular area ratio (MVR), which is the CD34-positive microvascular area compared to the total tumor area, was measured using StrataQuest. The predictive value of MVR on treatment outcome, assessed via progression-free survival (PFS), was evaluated using a multivariate Cox proportional hazard model. The median PFS in the high MVR group (≥0.058) was significantly shorter than that in the low MVR group (P=0.002). Multivariate analysis revealed that high MVR was an independent negative predictor of PFS (hazard ratio, 3.21 [95% CI: 1.18–8.76], P=0.022). High MVR may critically affect EGFR-TKI resistance in patients with NSCLC and EGFR mutations.

Purpose Microvessel density plays an essential role in tumor development. However, whether a tumor microenvironment, abundant in microvessels, affects epidermal growth factor receptor–tyrosine kinase inhibitor (EGFR-TKI) efficacy in patients with non-small cell lung cancer (NSCLC) and EGFR mutations remains unclear. We aimed to investigate the impact of tumor microvessels on EGFR-TKI efficacy in patients with NSCLC and EGFR mutations. Methods We retrospectively studied the data of 40 post-operative patients with recurrent NSCLC and EGFR mutations who received EGFR-TKIs as a first-line treatment at Kumamoto University Hospital between January 2010 and February 2021. Tumor sections were retrieved from the tissue registry and analyzed for CD34-positive microvessels using immunohistochemical techniques. The microvascular area ratio (MVR), which is the CD34-positive microvascular area compared to the total tumor area, was measured using StrataQuest. The predictive value of MVR on treatment outcome, assessed via progression-free survival (PFS), was evaluated using a multivariate Cox proportional hazard model. Results The median MVR and PFS values of EGFR-TKI were 0.058 (range, 0.013–0.094) and 610 d (range, 102–2807 d), respectively. The median PFS in the high MVR group (≥ 0.058) was significantly shorter than that in the low MVR group (P = 0.002). Multivariate analysis revealed that high MVR was an independent negative predictor of PFS (hazard ratio, 3.21 [95% CI: 1.18–8.76], P = 0.022). Conclusions High MVR may critically affect EGFR-TKI resistance in patients with NSCLC and EGFR mutations.