Regarding safety, THPy was associated with a higher incidence of grade 3/4 diarrhea (26.6% vs 3.1%) as well as increased rates of neutropenia, anemia, alanine aminotransferase elevation, fatigue, and peripheral neuropathy compared to THP.<h4>Conclusion and relevance</h4>Both THP and THPy are effective first-line options for HER2-positive MBC. The gene discussed is ERBB2; the disease is neutropenia.