P09.13 Bone Metastases and Overall Survival in Patients with Metastatic Non-Small Cell Lung Cancer Treated with Pembrolizumab

Abstract

Bone metastases (BM) and skeletal-related events (SRE) are a common cause of morbidity in patients with metastatic non-small cell lung cancer (mNSCLC). Data on the impact of BM on overall survival (OS) in patients treated with immune checkpoint inhibitors (ICI) is limited. Here we report the incidence, impact on survival, and risk factors for SRE in patients with mNSCLC treated with first-line pembrolizumab monotherapy or pembrolizumab plus chemotherapy. We conducted a retrospective study of patients with mNSCLC treated with first-line pembrolizumab or pembrolizumab plus chemotherapy at our institution from 2017-2020. The associations between SRE and categorical variables were studied using Fisher’s exact test and with continuous variables using the Kruskal-Wallis test. Kaplan-Meier plots were used to visualize survival curves. The association between baseline BM and OS was examined using a Cox proportional hazard model. OS was calculated from date of ICI initiation to death from any cause or last follow-up. We identified a cohort of 202 patients: 93 (46%) treated with pembrolizumab and 109 (54%) treated with pembrolizumab plus chemotherapy; 39 (19%) had squamous histology and 163 (81%) had nonsquamous histology; median age 62.7; median OS 33.7 months (95% CI: 17.2 – NR). In our cohort, 87 (43%) patients had BM at time of ICI initiation and 47 (23%) developed SRE after ICI initiation. Patients who developed SRE were more likely to have baseline BM than those without SRE (91.5% vs 28.4%, p<0.001). Development of BM during treatment with ICI and performance status were also significantly associated with SRE (p<0.001 and p=0.006, respectively). Patients with BM at time of ICI, or development of new or progression of existing BM while on ICI, had shorter survival than those without (Figure 1a and Figure 1b, respectively). In multivariate survival analysis, the hazard of death for patients with baseline BM was 2.85 times those without (HR=2.85, 95% CI: 1.53, 5.29, p-value=0.0009) after controlling for age, BMI, performance status, histology, PD-L1 expression, smoking, and SRE. The use of bone-modifying agents (BMA) was not associated with OS, osseous progression, or risk of SRE. The presence of BM at time of ICI was associated with shorter survival after controlling for multiple clinical characteristics. These patients represent a high-risk cohort for worse outcomes when treated with ICI alone or in combination with chemotherapy. In our cohort BMA were not associated with increased OS or decreased risk of osseous progression or SRE.