Artificial intelligence‐powered spatial analysis of tumor‐infiltrating lymphocytes as a biomarker in locally advanced unresectable thymic epithelial neoplasm: A single‐center, retrospective, longitudinal cohort study

BACKGROUND: Thymic epithelial tumors (TET) are rare malignancies and lack well‐defined biomarkers for neoadjuvant therapy. This study aimed to evaluate the clinical utility of artificial intelligence (AI)‐powered tumor‐infiltrating lymphocyte (TIL) analysis in TET. METHODS: Patients initially diagnosed with unresectable thymoma or thymic carcinoma who underwent neoadjuvant therapy between January 2004 and December 2021 formed our study population. Hematoxylin and eosin‐stained sections from the initial biopsy and surgery were analyzed using an AI‐powered spatial TIL analyzer. Intratumoral TIL (iTIL) and stromal TIL (sTIL) were quantified and their immune phenotype (IP) was identified. RESULTS: Thirty‐five patients were included in this study. The proportion of patients with partial response to neoadjuvant therapy was higher in the group with nondesert IP in preneoadjuvant biopsy (63.6% vs. 17.6%, p = 0.038). A significant increase in both iTIL (median 22.18/mm(2) vs. 340.69/mm(2), p < 0.001) and sTIL (median 175.19/mm(2) vs. 531.02/mm(2), p = 0.004) was observed after neoadjuvant therapy. Patients with higher iTIL (>147/mm(2)) exhibited longer disease‐free survival (median, 29 months vs. 12 months, p = 0.009) and overall survival (OS) (median, 62 months vs. 45 months, p = 0.002). Patients with higher sTIL (>232.1/mm(2)) exhibited longer OS (median 62 months vs. 30 months, p = 0.021). CONCLUSIONS: Nondesert IP in initial biopsy was associated with a better response to neoadjuvant therapy. Increased infiltration of both iTIL and sTIL in surgical specimens were associated with longer OS in patients with TET who underwent resection followed by neoadjuvant therapy.