Diefenhardt M, et al. - In the CAO/ARO/AIO-04 randomized phase 3 trial, including 1236 patients with rectal cancer treated with 5-FU-based preoperative chemoradiotherapy (CRT) alone or with oxaliplatin followed by surgery and adjuvant chemotherapy, researchers correlated baseline peripheral blood leukocytes, neutrophils, hemoglobin, platelets, lactate dehydrogenase and carcinoembryonic antigen (CEA) with clinicopathologic features as well as clinical outcome, to assess the role of peripheral blood leukocytosis and neutrophilia as prognostic immunological biomarkers in these patients. For disease-free survival (DFS), distant metastasis and overall survival, baseline leukocytosis was identified as an independent adverse prognostic factor. For neutrophilia and high CEA levels, similar important findings were observed. Only in patients with neutrophilia and leukocytosis, a significant DFS improvement was noted in relation to the addition of oxaliplatin to 5-FU CRT. High-level evidence was found for the adverse prognostic role of leukocytes and neutrophils.