Blood T cell diversity associated with the prognosis of advanced non‐small cell lung carcinoma treated with first‐line pemetrexed based chemotherapy

BACKGROUND: The tumor microenvironment is associated with prognosis in advanced non‐small cell lung carcinoma (NSCLC). The aim of this study was to explore the relationship between blood T cell diversity and survival of patients treated with pemetrexed‐based chemotherapy for nonsquamous NSCLC. METHODS: This prospective clinical study enrolled 26 patients with advanced NSCLC treated with 4–6 cycles of first‐line pemetrexed combined with platinum‐based therapy. The complementarity‐determining region 3 (CDR3) located in the T cell receptor beta chain (TCR β chain) was captured and deeply sequenced using next‐generation sequencing (NGS) technology, and the correlation between TCR changes and efficacy after chemotherapy was analyzed. RESULTS: Patients with an inferior quarter diversity index showed a significantly shorter progression‐free survival (PFS) than the others (median, 5.0 months vs. 8.1 months, P = 0.014). After two cycles of chemotherapy, the TCR diversity was significantly higher than the baseline (P = 0.034). Just as with the baseline, patients with an inferior quarter diversity index at the endpoint of cycle 2 showed a shorter progression‐free survival (PFS) than the others (median, 5.0 months vs. 8.4 months, P = 0.024). CONCLUSIONS: In advanced NSCLC patients treated with first‐line pemetrexed combined with platinum, the low level of blood TCR diversity at baseline with an endpoint of two cycles of chemotherapy was correlated with a poor prognosis.