Objectives Treatment of ovarian cancer (OC) is challenged by advanced stage at diagnosis, development of resistance to chemotherapy resulting in low response rates. Natural killer (NK) cells are a subset of lymphocytes with antitumor capabilities however, the clinical significance remains unclear. The study aimed to investigate if blood NK cells could predict treatment effect in patients with recurrent ovarian cancer.

Methods Patients receiving chemotherapy for recurrent OC at Vejle Hospital were included (N=72). Blood samples were drawn before treatment cycles. Lymphocytes, NK cells and neutrophils were investigated through flowcytometry and NK cell activity was measured by the NK Vue® assay with interferon gamma as a marker. Progression free survival (PFS) was the primary endpoint.

Results Patients with high vs low NK cell count at 2nd treatment cycle (cut off: 184 cells/µL) had a median PFS of 7.3 months vs 3.1 months (p=0.0027) (figure 1). No significant correlation was found regarding NK cell activity and PFS. Patients with low vs high neutrophil lymphocyte ratio at 2nd treatment cycle (Cut off: 3.8) had a median PFS of 6.5 months vs 2.7 months (p= 0.0078). In multivariate Cox regression analysis NK cell count at 2nd treatment cycle remained an independent marker of favorable PFS with an adjusted hazard ratio (HR) of 0.39 (p=0.008).

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Abstract 59 Figure 1

PFS NK cell count at 2nd treatment cycle

Conclusions A significant correlation between NK cells and treatment outcome in OC was found. This could influence future chemotherapy strategy and support research regarding NK cell based treatment.