Trastuzumab induces gastrointestinal side effects in HER2-overexpressing breast cancer patients

Summary   Purpose: To characterise the gastrointestinal toxicities associated with Trastuzumab administration in HER2-overexpressing breast cancer patients. Methods: All patients (n = 46) who received Trastuzumab as a single agent or in conjunction with conventional anti-cancer treatment within the Royal Adelaide Hospital Cancer Centre from 2002–2007 were included in this study. A retrospective analysis of case-notes was conducted to investigate the toxicities associated with Trastuzumab. Results: Trastuzumab as a single agent induced toxicities following 22% of administrations. Gastrointestinal toxicities were observed following 12% of administrations and included nausea and vomiting, diarrhoea, abdominal pain and bloating. However, other prominent toxicities that were not related to the gastrointestinal tract were also observed including fatigue and lung symptoms (10.4%). Elderly patients (≥60 years) and those with metastatic disease experienced the highest frequency of toxicity. Conclusion: Trastuzumab induces a range of gastrointestinal toxicities in HER2-overexpressing breast cancer patients. These toxicities are separate to those caused by concurrent chemotherapy and/or radiotherapy.