Background
Use of immune checkpoint inhibitors against advanced stage NSCLC has been associated with significant reduction in overall disease morbidity and mortality. However, despite the significant survival benefit, tumors invariably relapse. It is important to understand the pattern of progression and the progression free survival (PFS) to better predict disease outcomes and modify treatment approach.
Methods
We performed a retrospective review of 74 veterans with new diagnosis of stage IV NSCLC who received 2 or more cycles of immunotherapy with/without concurrent chemotherapy between 2015-2021 at the Stratton VA Medical Center. IRB approval was obtained. Fisher exact probability test and Kaplan-Meier estimators were used to analyze data with level of significance P < .05.
Results
Out of 74 patients, 38 patients were identified who received immunotherapy alone (Group A; n = 23, 60.5%) vs chemo-immunotherapy (Group B; n = 15, 39.5%). Baseline characteristics of Group A revealed median age 70 (IQR, 65-78), adenocarcinoma (n = 10, 43.4%), squamous cell carcinoma (n = 12, 52.1%), PD-L1 > 50% expression (n = 21, 91.3%), molecular testing positive for EGFR in 1 patient, otherwise negative for ROS, ALK, EGFR and BRAF mutations in all patients. Similarly, in Group B, median age 66 (IQR, 63-72), adenocarcinoma (n = 6, 40%), squamous cell carcinoma (n = 8, 53.3%), PD-L1 > 50% expression (n = 3, 20%), no mutations noted on molecular testing. Out of 38 patients, disease progression was noted in 19 patients, 10 in Group A (progression at initial site and new site n = 5, 50%) vs 9 in Group B (progression at initial site and new site, n = 6, 66.7%). Most common sites of progression included local and distant lymph nodes, brain, bone, and liver. Using the Kaplan-Meier analysis, median progression free survival (PFS) from start of immunotherapy till evidence of progression on imaging was 11 months in Group A and 7 months in Group B, P = .22. Our study recognized widespread metastases at the time of diagnosis (P = .03) as a possible factor affecting progression of diseases in Group A compared to Group B.
Conclusion
We conclude that although no statistically significant association was noted between the progression free survival between the two groups, the increased median PFS in immunotherapy only group is worth additional investigation. We recommend further large-scale studies to explore this association.