Incidence and Management of Diarrhea With Adjuvant Pertuzumab and Trastuzumab in Patients With Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer

BackgroundThe APHINITY (BIG 4-11) study showed that pertuzumab significantly improved the rates of invasive disease-free survival among patients with human epidermal growth factor receptor 2 (HER2)-positive, operable breast cancer when added to adjuvant trastuzumab and chemotherapy. Because diarrhea was a common adverse event that could compromise treatment administration, we evaluated the incidence and management of diarrhea in the APHINITY study.Patients and MethodsThe APHINITY trial is a prospective, randomized, multicenter, multinational, double-blind, placebo-controlled trial. The eligible patients were randomly assigned to receive standard adjuvant chemotherapy and 1 year of trastuzumab combined with pertuzumab or placebo. The diarrhea incidence, severity (National Cancer Institute common terminology criteria for adverse events, version 4.0), onset, and management were analyzed.ResultsA total of 4805 patients were randomized. Diarrhea of any grade was the most common adverse event and occurred in 71% of patients in the pertuzumab arm versus 45% in the placebo arm. Diarrhea grade 3 to 4 was observed in 10% and 4% in the pertuzumab and placebo arms, respectively. The greatest incidence of diarrhea was reported during the concomitant administration of HER2-targeted therapy and taxane (61% vs. 34% of patients experienced an event with pertuzumab vs. placebo, respectively). A marked decrease was observed on chemotherapy cessation. Antidiarrheal agents were commonly used, and diarrhea rarely caused treatment dose modifications or discontinuation.ConclusionDiarrhea was a common adverse event in the APHINITY study. Most episodes were low grade and were generally manageable with common antidiarrheal agents. The incidence of diarrhea was greater with the combination of a taxane and HER2-targeted treatment and decreased once chemotherapy was stopped.