Treatment selection and real-world analysis of immunotherapy with or without chemotherapy in PD-L1-high metastatic non-small cell lung cancer

Background: Lung cancer is the leading cause of cancer death in Australia. Immunotherapy has improved outcomes in patients with metastatic non-small cell lung cancer (NSCLC). Pembrolizumab is approved in first-line treatment as single-agent immunotherapy (SAI) or combination chemoimmunotherapy (CIT). In metastatic NSCLC programmed death-ligand 1 (PD-L1) >= 50% either regimen may be used. Aims: We aim to identify patient and tumour characteristics that influence treatment selection. Methods: This is a retrospective observational study. Pharmacy records identified patients with metastatic/recurrent NSCLC receiving pembrolizumab at two metropolitan centres in Victoria, Australia, since 2018. Demographics, tumour characteristics, Charlson Comorbidity Index (CCI) and treatment data were collected. Descriptive and multivariate analyses were performed. Results: Sixty-one patients had metastatic NSCLC PD-L1 >= 50% and received pembrolizumab with median age of 65.6 years, Eastern Cooperative Oncology Group 0-1 in 82%. CIT was administered to 23% (14) with no difference in rate of delivery between centres (P = 0.808). CCI mean score differed (3.38 SAI vs 2.36 CIT, P = 0.042). Patients with high CCI score ( >= 2) were less likely to receive CIT (OR = 0.15, P = 0.003, 95% confidence interval (CI) 0.04-0.57). Primary tumours over 5 cm were more likely to receive CIT (OR = 3.74, P = 0.043, 95% CI = 1.04-13.42). Site-specific metastases of liver, brain and pericardial effusion were not associated with CIT. Conclusions: Patients with higher comorbidity score were less likely to receive CIT, suggesting chemotherapy avoidance in comorbid patients. Larger tumours are associated with CIT use, indicating that oncologists may use tumour size as a surrogate of disease burden. Limitations include small sample size and data cut-off. Future prospective studies could incorporate comorbid status and a validated disease burden score to stratify patients.