Diarrhea is a common but manageable side effect for patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer undergoing treatment with pertuzumab, according to a study published in Annals of Oncology.1

Researchers evaluated 1443 patients with HER2-positive breast cancer, 804 of whom had metastatic disease identified through the CLEOPATRA trial, as well as 416 and 223 patients who had early-stage disease and were found through the NeoSphere and TRYPHAENA trials, respectively. This study’s goal was to determine the incidence and severity of diarrhea depending on the type of treatment patients received.

All-grade diarrhea incidence was “generally greater” for patients given pertuzumab-based treatment, at 21 to 54% for grade 1, 8 to 37% for grade 2, and 0 to 12% for grade 3, with no incidence of grade 4 diarrhea. The highest rate of incidence was noted during the first cycle of treatment.

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Rates of dose delays or discontinuations because of diarrhea had ranged from 0 to 8%, and the rates of patients who experienced both diarrhea and febrile neutropenia ranged from 0 to 11%. The researchers found no relation between diarrhea and pre-existing gastrointestinal comorbidities.

Patients in the CLEOPATRA trial who were at least 65 years of age and treated with pertuzumab had a higher incidence of grade 3 diarrhea compared to those less than 65 years of age.

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The researchers concluded that diarrhea was a “common but manageable” side effect among these patients treated with pertuzumab-containing regimens in both the metastatic and early-stage setting.


  1. Swain SM, Schneeweiss A, Gianni L, et al. Incidence and management of diarrhea in patients with HER2-positive breast cancer treated with pertuzumab. Ann Oncol. 2017 Jan 5. doi: 10.1093/annonc/mdw695 [Epub ahead of print]