AIM: The aim of this study was to describe the dynamic changes in blood work following individual adjusted dosage of intravenously administered iron(III)isomaltoside in a 4-week period prior to surgery in patients with colorectal cancer.

METHODS: This was a single-center, observational cohort study with prospectively collected data, including patients with colorectal cancer receiving preoperative treatment with iron(III)isomaltoside. Blood samples were taken at baseline, one week, two weeks, and four weeks after initial treatment. Sixty-two patients were included in the study.

RESULTS: Sixty-two patients were included for final analysis. The mean increase in haemoglobin was 0.77 g/dL (95% CI: 0.52-1.03, p<0.0001) at week 1, 1.5 g/dL (95% CI: 1.21-1.80, p<0.0001) at week 2, and 2.13 g/dL (95% CI: 1.71-2.55, p<0.0001) at week four. Patients with severe anaemia (<9.02 g/dL) showed the largest increase in haemoglobin during the treatment course (2.92 g/dL (95% CI: 2.27-3.58 g/dL, p<0.0001). Patients with mild anaemia (>10.31 g/dL) did not show a significant increase (0.66 g/dL (95% CI: -0.29-1.61, p=0.17) The mean of transferrin saturation after four weeks was 8% (95% CI: 6%-10%, p<0.0001).

CONCLUSIONS: After intravenously administered iron, patients with severe anaemia had the most substantial increase in haemoglobin, and the increase was largest after four weeks. Patients with mild anemia did not have an increase in haemoglobin during the treatment course. The vast majority of patients still had iron deficiency at surgery four weeks after the initial treatment.