NK cell expansion after primary multimodal treatment to predict progression free survival in inoperable stage III NSCLC.

Abstract

e20584 Background: During multimodal cancer therapy an acute lymphocytopenia occurs, which is associated with poor survival in inoperable stage III NSCLC patients. A prospective analysis of peripheral blood mononuclear cells (PBMCs) during multimodal treatment was performed to assess dynamic changes of leukocyte subpopulations after concurrent chemo-radioimmunotherapy (cCRT) in order to extract biomarkers to predict progression free survival (PFS). Methods: 20 patients (17 male, 3 female), at median age of 65.5 years (range 34 to 79), 11 suffering from adenocarcinoma, 8 squamous cell carcinoma, and 1 undifferentiated NSCLC, were enrolled in the study. They received thoracic radiotherapy (TRT, 2/20, 10%), cCRT (11/20, 55%), or cCRT with checkpoint inhibition (cCRT-ICI, 7/20, 35%), one patient (1/20, 5%) withdrew consent and was excluded from analysis. Patients were grouped into poor ( < 6months), intermediate (≥6 < 12 months), or favorable (≥12 months) PFS. Blood was analyzed via flow cytometry for leukocyte sub-populations at 9 time points. Here, we report on NK cells and focus on the time period starting after end of TRT until 6 months thereafter. The area under curve (AUC) of absolute cell counts for this period was calculated to provide an aggregate measure for the time-course dynamics. Results: NK cell counts were consistently low in all patients at the end of TRT. Patient-individual recovery of cell counts 6 months after RTend (expressed as the AUC) was observed, which was beneficially affected by consolidation ICI (one-tailed t-test, p = 0.031). Retrospective assignment of the AUC values to the PFS groups revealed a positive association of high AUC values with PFS. Patients with longest PFS (≥12 months; 9/19) had higher AUC values compared to patients with intermediate PFS (≥6 < 12 months; 5/19; t-test p = 0.043) or poor PFS ( < 6months; 5/19; p = 0.0018). The difference between AUC values of intermediate and poor PFS groups was also significant (p = 0.039). Conclusions: Patients who responded with early NK cell expansion after TRT, cCRT, or cCRT-ICI had significantly longer PFS compared to those without increase. Longitudinal monitoring of NK cells and calculating the AUC (RTend and 6 months thereafter), which reflects absolute cell counts, is a promising biomarker to predict PFS.