92P - Reduction in the relative lymphocyte count as a predictive biomarker for serious immune-related adverse events in patients with metastatic non-small cell lung cancer on immunotherapy: Single institution experience

Background

The relative lymphocyte count (RLC) is a simple and widely available host-related biomarker. RLC is explored as a potential marker of immune checkpoint inhibitor therapy outcomes in patients with non-small-cell lung cancer (NSCLC). The objective of this study was to investigate the predictive value of RLC reduction for occurrence of serious immune-related adverse events (sirAEs) in patients with metastatic NSCLC, treated in the clinic of Medical oncology of Military Medical Academy in Sofia, Bulgaria.

Methods

The information was obtained retrospectively from the medical documentation of the pts with metastatic NSCLC, treated with immunotherapy (mono or in a combination with chemotherapy) in our institution in the period from m.05.2018 to m.05.2023. Descriptive statistical analysis was used. The RLC is measured at the onset of treatment and compared with the RLC at the time of diagnosis of irAEs. For the pts without irAEs the comparison is made between the initial RLC, normal or abnormal, and the occurrence of reduction in RLC during the course of treatment. As a reduction in RLC is defined as the drop of the lymphocyte count with more than 50% of the initial value if the lower RLC value is under 20% of the WBC.

Results

Thirty four pts with metastatic NSCLC were treated with immunotherapy (first, second or consecutive line) in our institution during the last 5 years. 3/34 (9%) were diagnosed with grade 1 or 2 irAEs, 5/34 (15%) with sirAEs (grade 3 to 5). In 4/5 (80%) of the cases with sirAEs we observed a reduction in RLC. 0/3 (0%) of the pts with grade 1 or 2 irAEs and 9/26 (35%) of the pts without immune-related toxicities met the criteria for RLC reduction. The pts with sirAEs had significantly higher RLC reduction rate than the pts with low grade or without immune-related toxicities. The χ² statistic was 8.6595, leading to a p-value of 0.03745.

Conclusions

Our data suggest that RLC reduction is a strong predictive biomarker for sirAEs (p<0.05). The underlying pathophysiologic mechanism of this observation remains to be determined.

Editorial acknowledgement

N/A

Clinical trial identification

N/A

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.