Prognostic impact of leukocyte counts before and during radiotherapy for oropharyngeal cancer.

Introduction: Peripheral blood count components are accessible and evidently predictive in other cancers but have not been explored in oropharyngeal carcinoma. We examine if there is an association between the use of intensity-modulated radiotherapy (IMRT) or intensity-modulated proton therapy (IMPT) and lymphopenia, as well as if there is an association between baseline neutrophilia, baseline leukocytosis and lymphocyte nadir in oropharyngeal cancer.

Materials and Methods: Analysis started with 150 patients from a previous case to case study design, which retrospectively identified adults with oropharyngeal carcinoma, 100 treated with IMRT in 2010-2012 and 50 treated with IMPT in 2011-2014. Pretreatment leukocyte, neutrophil, lymphocyte, and hemoglobin levels were extracted, as were neutrophil and lymphocyte nadir levels during radiotherapy. We retained 137 patients with recorded pre-treatment leukocyte and neutrophil levels for associated analysis and 114 patients with recorded lymphocyte levels during radiation and associated analysis. Multivariate survival analyses were done with Cox regression.

Results: The radiotherapy type (IMRT vs. IMPT) was not associated with lymphopenia (grade 3 P  > .99; grade 4 P  = .55). In univariate analyses, poor overall survival was associated with pretreatment neutrophilia (hazard ratio [HR] 5.58, 95% confidence interval [CI] 1.99-15.7, P  = .001), pretreatment leukocytosis (HR 4.85, 95% CI 1.73-13.6, P  = .003), grade 4 lymphopenia during radiotherapy (HR 3.28, 95% CI 1.14-9.44, P  = .03), and possibly smoking status >10 pack-years (HR 2.88, 95% CI 1.01-8.18, P  = .05), but only T status was possibly significant in multivariate analysis (HR 2.64, 95% CI 0.99-7.00, P  = .05). Poor progression-free survival was associated with pretreatment leukocytosis and T status in univariate analysis, and pretreatment neutrophilia and advanced age on multivariate analysis.

Conclusions: Treatment modality did not affect blood counts during radiotherapy. Pretreatment neutrophilia, pretreatment leukocytosis, and grade 4 lymphopenia during radiotherapy were associated with worse outcomes after, but establishing causality will require additional work with increased statistical power.