Clinical significance of BIM-deletion polymorphism on chemoradiotherapy in patients with non-small cell lung cancer.

Abstract

e21536 Background: The standard treatment for locally advanced non-small cell lung cancer (NSCLC) is chemoradiotherapy (CRT) followed by anti-programmed cell death-ligand 1 (PD-L1) drug therapy. BIM deletion induces apoptosis suppression and the effect of epidermal growth factor-tyrosine kinase inhibitor is reportedly attenuated in EGFR-mutated NSCLC patients with BIM deletion. This study retrospectively examined the effects of BIM deletion on CRT or PD-1 treatment in patients with NSCLC. Methods: Among patients with unresectable NSCLC at Higashi-Hiroshima Medical Center and Hiroshima University Hospital between April 1994 and April 2018, we enrolled those treated with CRT or chemotherapy using carboplatin + paclitaxel or cisplatin + vinorelbine, or PD-1 antibody treatment. Results: Of 1,224 patients with unresectable NSCLC, 88, 80, and 79 underwent CRT, chemotherapy, or PD-1 antibody treatments, respectively. Within these treatment groups, 15 (17%), 15 (19%) and 11 (14%) patients, respectively, had BIM deletion. Among patients receiving CRT, the progression-free survival and overall survival were significantly shorter in those with BIM deletion than in those without (150 vs. 254 days, p = 0.003; 429 vs. 710 days, p = 0.03). Moreover, multivariate Cox regression analysis showed BIM deletion to be an independent factor for anti-tumor effect or prognosis (hazard ratio [95% confidence interval] 2.042, [1.112–4.039], p = 0.029; 2.414, [1.063–4.984], p = 0.036). These results were not observed in the chemotherapy and PD-1 treatment groups. To confirm the association between radiation therapy effect and BIM deletion, we performed in vitro experiments using two NSCLC cell lines (A549 and EBC-1). Suppressed BIM expression using siRNA (instead of BIM deletion) in these cells showed significantly suppressed antitumor effect and apoptosis 48 hours after 30-Gy irradiation but not chemotherapy. Conclusions: We showed that BIM deletion is an independent anti-tumor effect or prognostic factor for CRT. The results also indicated that BIM deletion was associated with the effects of radiation but not chemotherapy or PD-1 antibody treatment.