Associations of Pretreatment Hemoglobin, Body Mass Index, and Leukocyte Count with Acute and Late Toxicity During and After Radiotherapy for Rectal Cancer

Background/Objectives: Radiotherapy is an important component of rectal cancer treatment, but treatment-related toxicity varies considerably between patients, suggesting that patient-related factors may influence susceptibility. Pretreatment hemoglobin, leukocyte count, and body mass index (BMI) are routinely available measures, yet their associations with acute and late toxicity during and after radiotherapy remain unclear. This study evaluated these associations in patients with rectal cancer. Methods: A retrospective analysis included 67 patients with histologically confirmed rectal cancer who underwent radiotherapy. Acute toxicity occurred during radiotherapy or within 3 months after treatment completion, and late toxicity occurred thereafter. Toxicity was graded using the Common Terminology Criteria for Adverse Events (CTCAE) and dichotomized as Grades 0–1 or Grade ≥ 2. Pretreatment hemoglobin, total leukocyte count, and BMI were analyzed as continuous variables. Logistic regression examined associations with acute and late toxicity, with sequential adjustment for age, sex, and radiotherapy course. Results: Grade ≥ 2 acute toxicity occurred in 17 patients (25.4%), and Grade ≥ 2 late toxicity in 27 (40.3%). Higher pretreatment leukocyte count was associated with greater odds of acute toxicity in the fully adjusted model (OR 1.70, 95% CI 1.13–2.58; p = 0.012). Higher pretreatment hemoglobin was associated with lower odds of late toxicity in the fully adjusted model (OR 0.57, 95% CI 0.40–0.81; p = 0.002). No clear association was observed between BMI and either acute or late toxicity. Conclusions: Pretreatment leukocyte count was associated with acute toxicity, while pretreatment hemoglobin was associated with late toxicity. These inexpensive, routinely available measures may represent candidate markers of toxicity, although their clinical utility requires validation in larger, independent studies.