Background The standard treatment for rectal cancer stage II-–III is neoadjuvant chemoradiotherapy based on oral capecitabine (CPC) or continuous 5-fluorouracil (5-FU) infusion. While efficacy has been demonstrated to be equivalent between the two treatments, there is a discrepancy over safety.

Purpose To assess the incidence of adverse events (AE) between CPC and 5-FU in neoadjuvant chemoradiotherapy for rectal cancer to compare the safety profiles of both treatments.

Material and methods This was an observational, retrospective study on patients treated with CPC (1650 mg/m²/day) or 5-FU (225 mg/m²/day) from 2012 to 2018. Data was obtained from medical records and the oncology software Oncofarm. AE (reported as Grade 1–2 or ≥3), dose reductions, treatment interruptions and administration-related AE were assessed.

Results Seventy-six patients were included, 32 treated with CPC and 44 with 5-FU. Mean age was 63.1 (10.1)^a in the CPC group and 62.3 (11.8)^a in the 5-FU group. Sex: 24 (75.0%) in the CPC group and 34 (77.3%) in the 5-FU group were men. Adverse events: 36 AE G1–2 and 2 AE G≥3 were reported in the CPC group; and 61 AE G1–2 and one AE G≥3 were reported in the 5-FU group. Two patients in the CPC group reduced doses for diarrhoea and palmar–plantar erythrodysesthaesia (PPE) and three patients discontinued the treatment for diarrhoea, PPE and fatigue with anorexia; and one patient in the 5-FU group reduced doses for PPE.

^avalues are mean (SD).

Conclusion While the CPC group had a lower incidence of AE except for PPE, they had more dose reduction and treatment interruption. A posterior analysis showed that dose reduction and treatment interruption in the CPC group happened in the last week of treatment. In disagreement with previous studies, 5-FU patients had a higher incidence of diarrhoea.

References and/or acknowledgements No conflict of interest.