Abstract 123P
Background
Immune checkpoint inhibitors (ICI) can significantly improve cancer outcomes, but are not universally effective and are costly. Existing biomarkers are inconsistently predictive of outcome. We explored the relationship between lymphocyte count and time to progression (TTP) for patients on ICI.
Methods
A retrospective review of patients in two institutions was performed, identifying any patients treated with at least two doses of PD-1 inhibitors for an approved indication between 2013 and 2019. Baseline clinicopathologic characteristics, bloodwork at treatment initiation and three months, and survival data were obtained. Ethical approval was obtained locally.
Results
Overall 179 patients met the inclusion criteria with 60 (33.5%) demonstrating a partial or complete response, and 100 (55.9%) patients progressing at some point. Median TTP was 3.8 months. Those with baseline lymphocyte count <1.0x109 had no significant difference in TTP compared to those who were not lymphopenic (6.5 vs 10.8 months, p=0.482). However, those with lymphocyte count <1.0x109 at 3 months had significantly shorter time to progression compared to those who were not lymphopenic at 3 months (5.3 vs 15.1 months, p=0.005). There was no significant difference in time to progression between patients who were initially lymphopenic but recovered counts at three months, and those who were never lymphopenic. On multivariate analysis, prior radiation therapy was the factor most associated with lymphopenia at baseline (OR 6.15, p<0.001) and at three months (OR 3.33, p=0.001).
Conclusions
In this retrospective review, we identified lymphopenia at three months as being a poor prognostic marker among patients being treated with ICI, whereas those with baseline lymphopenia who subsequently recovered counts had a prognosis equal to those with persistently normal lymphocyte counts.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.