Bone metastasis attenuates efficacy of immune checkpoint inhibitors and displays "cold" immune characteristics in Non-small cell lung cancer

Objectives: This study aimed to assess the clinical characteristics affecting outcomes after immune checkpoint inhibitors (ICI) therapies in non-small cell lung cancer (NSCLC) patients, and the underlying mechanism in tumor immune micro-environment (TIME).

Materials and methods: A total of 144 patients treated with ICI-based strategies were retrospectively analyzed. Expression of 10 immune antibodies in tumor tissues from other 60 untreated NSCLC patients were sequentially tested using multiplexed immunofluorescence (mIF) staining method. Correlation of clinical characteristics with ICI treatment outcomes and TIME characteristics were analyzed.

Results: Multivariate logistic and cox regression indicated that BoM negatively affected disease control rate (OR = 0.32, 95%CI: 0.13-0.82, P = 0.018), progression free survival (HR = 3.44, 95% CI:1.97-6.00, P < 0.001) and overall survival (HR = 3.24, 95% CI:1.62-6.50, P = 0.001), irrespective of programmed death-ligand 1 (PD-L1) expression. BoM patients were with significantly lower PD-L1, and this heterogeneity of TIME was then confirmed in the mIF staining, where 36 (61.0%) patients were clustered into immune-subtype A, with low expression of all the detected immune markers, similar to "cold" tumors, and 23 (39.0%) in cluster B with likely "hot" tumors. More patients in immune-subtype A were non-smokers (63.9% vs. 39.1% P = 0.063), with BoM (66.7% vs. 21.7%, P = 0.001), in stage IV(88.9% vs. 65.2%, P = 0.045), and with adenocarcinoma (91.7% vs. 69.6%, P = 0.037). Multivariate logistic regression indicated that BoM was independently associated with the "cold" immune characteristics (OR = 0.19, 95% CI:0.04-0.84, P = 0.028). Combination therapy with chemotherapy /antiangiogenesis or use of bisphosphonate during ICI treatment significantly improved clinical outcomes in BoM patients.

Conclusions: BoM displays adverse impact on clinical outcomes after ICI treatments in NSCLC patients. The "cold" characteristics of TIME may be the underlying mechanism for the attenuated efficacy of ICIs in bone metastatic NSCLC patients.