Development of acneiform rash does not predict response to lapatinib treatment in patients with breast cancer

Study Objective To determine if development of acneiform rash is a predictor of objective response rate with lapatinib. Design Subanalysis of data from a prospective, phase II study. Setting Academic breast care clinic. Patients Forty-nine treatment-naïve patients with human epidermal growth factor receptor-2 (HER2)-positive locally advanced breast cancer, who were treated with neoadjuvant lapatinib monotherapy for 6 weeks; 47 patients were included in the final analysis. Measurements and Main Results Of the 49 patients enrolled, 33 (67%) developed a rash of any type, and 26 (55%) had acneiform rash. Of the 26 evaluable patients with acneiform rash (55%), 19 (73%) responded to lapatinib and 7 (27%) did not. Of the 21 evaluable patients without acneiform rash, 11 (67%) responded to treatment and 7 (33%) did not. Thus, no association was found between the occurrence of acneiform rash and response to lapatinib monotherapy. Conclusion This study does not support the development of the acneiform rash as a predictor of clinical efficacy of lapatinib in the treatment of breast cancer.