Maturation and abundance of tertiary lymphoid structures are associated with the efficacy of neoadjuvant chemoimmunotherapy in resectable non-small cell lung cancer.

Tertiary lymphoid structures (TLS) existence is correlated with favorable prognosis in many types of cancer including non-small cell lung cancer (NSCLC). However, TLS formation and its relationship with treatment response remains unknown in NSCLC who received anti-PD-1 antibody plus chemotherapy as the neoadjuvant treatment (neoadjuvant chemoimmunotherapy). Here, we investigate TLS maturation and abundance in resectable NSCLC receiving neoadjuvant treatments. We retrospectively collected formalin-fixed paraffin embedded (FFPE) tissues from patients with resectable NSCLC (stage II-IIIA) from three cohorts based on treatment: naïve (N=40), neoadjuvant chemoimmunotherapy (N=40), and neoadjuvant chemotherapy (N=41). The TLS in tumor tissues was detected by immunohistochemical staining, and the differences in TLS maturation and abundance among different treatment groups were analyzed, as well as the relationship with pathological response and prognosis of patients. Multiplex immunofluorescence staining was used to explore the features of immune microenvironment. Higher major pathological response (MPR) rate and pathological complete response (pCR) rate were in the neoadjuvant chemoimmunotherapy group than in the neoadjuvant chemotherapy group (MPR: 45.0% vs 17.1%; pCR: 35.0% vs 4.9%). Among the three cohorts, neoadjuvant chemoimmunotherapy-treated NSCLCs displayed highest TLS maturation and abundance. Both the maturation and abundance of TLS were significantly correlated with MPR in both the neoadjuvant chemoimmunotherapy and the chemotherapy group. Patients with high maturation and abundance of TLS exhibited better disease-free survival (DFS) in all the three cohorts. TLS maturation was also an independent predictor for DFS in the neoadjuvant chemoimmunotherapy and treatment naïve group. Multiplex immunohistochemistry analysis using paired biopsy-surgery samples showed increased infiltration of CD8+T cell and decreased infiltration of M1 and M2 macrophages after neoadjuvant chemoimmunotherapy treatment in patients achieving MPR. There were no significant differences in features of immune cell infiltration for those with mature TLS achieving MPR when cross-compared across the three cohorts. These results demonstrate that TLS maturation is associated with MPR and an independent predictor for DFS in resectable neoadjuvant chemoimmunotherapy-treated NSCLC. The induction of TLS maturation may be a potential mechanism of action of neoadjuvant chemoimmunotherapy in resectable NSCLC.