Retrospective Analysis of the Safety of Herceptin® Immunotherapy in Metastatic Breast Cancer

Approximately 25,000 patients have been treated to date with the humanized anti-HER2 monoclonal antibody, Herceptin. This therapy has proved effective and well tolerated in patients with HER2-positive metastatic breast cancer; adverse events were generally infusion-related fever and chills of mild-to-moderate severity. Cardiotoxicity and infusion-related reactions emerged as the two main safety concerns with the use of Herceptin. Retrospective analysis revealed a higher incidence of heart failure when Herceptin was combined with anthracyclines than that expected with anthracyclines alone. Age, anthracycline exposure and cardiac risk factors were found to be predictors of cardiac adverse events. Patients experiencing cardiac dysfunction responded well to standard cardiac medication and the majority improved. Cardiac function should be monitored regularly and Herceptin should be discontinued if significant heart failure develops unless the benefits for an individual patient outweigh the risks. Of 25,000 patients, 74 (0.3%) were reported to have experienced a serious infusion-related reaction. The majority occurred during or shortly after the first infusion and were characterized by respiratory symptoms. Most patients were successfully treated; a total of 33 patients continued Herceptin therapy with no recurrence of infusion reactions. Although the benefit to risk ratio of Herceptin remains favorable, physicians must be vigilant and aggressive in managing cardiotoxicity and infusion-related reactions.