Elevated Absolute Monocyte Count, Absolute Neutrophil Count, and Neutrophil-to-Lymphocyte Ratio as Prognostic Factors in Locally Advanced Pancreatic Cancer Patients Treated With Stereotactic Body Radiation Therapy

Abstract

Stereotactic body radiation therapy (SBRT) is an emerging treatment modality for locally advanced pancreatic cancer (LAPC), yet is still associated with a high mortality rate. We therefore sought to determine prognostic factors associated with overall survival in LAPC patients undergoing SBRT. Given the established association between inflammation and survival for pancreatic cancer, we focused on hematological markers of inflammatory response: absolute monocyte count (AMC), absolute neutrophil count (ANC), and the neutrophil-to-lymphocyte ratio (NLR). We retrospectively analyzed a cohort of LAPC patients (n = 27) treated with SBRT to a total cumulative dose of 33 Gy (6.6 Gy x 5 fractions). Prior to SBRT, 22 (82%) patients received chemotherapy (either gemcitabine-based [86%] or FOLFIRINOX-based [14%]). Two month post-treatment values were selected and cut-off values for AMC (≥750), ANC (≥3900), and NLR (≥9) were established. Survival analysis was performed using Kaplan-Meier estimates and a Cox proportional hazard model. As defined by our cut-offs, elevated AMC, ANC, or NLR values were observed in 22%, 37%, and 30%, respectively, in our cohort of SBRT treated patients. Median overall survival for patients with AMC ≥750 and AMC <750 was 6.1 and 11.7 months, respectively; ANC ≥3600 and ANC <3600 was 4.9 and 18.4 months, respectively; NLR ≥9 and NLR <9 was 4.5 and 14.1 months, respectively. Elevated AMC (HR = 8.3, p = 0.005), elevated ANC (HR = 32.6, p = 0.001), or elevated NLR (HR = 6.4, p = 0.003) were found to be prognostic factors for overall survival. In our cohort of SBRT treated LAPC patients, post-treatment levels of monocytes, neutrophils, and NLR represent prognostic factors associated with overall survival. Given that neutrophils and monocytes respond to and contribute towards inflammation and that the NLR is an established marker of systemic inflammation, these findings are in line with established data linking inflammation and poor cancer survival. The low cost and routine availability of these values supports these hematological markers as potentially valuable biomarkers for predicting disease outcome.