Can rash associated with HER1/EGFR inhibition be used as a marker of treatment outcome?

Rash is a class effect of HER1/epidermal growth factor receptor (EGFR)-targeted agents, and has occurred with high frequency and in a dose-dependent manner in clinical trials of these agents in cancer patients. Analysis of phase II trials of erlotinib (Tarceva) in non-small-cell lung cancer, head and neck cancer, and ovarian cancer shows a significant association between rash severity and objective tumor response. Rash severity was highly significantly associated with survival in patients with non-small-cell lung cancer receiving erlotinib; median survival in patients with no rash was 46.5 days, compared with 257 days in those with grade 1 rash (P < .0001) and 597 days in those with grade 2/3 rash (P < .0001). Similarly, for the combined non-small-cell lung cancer, head and neck cancer, and ovarian cancer studies, median survival in patients with no rash was 103 days, compared with 191 days in those with grade 1 rash (P = .0001) and 266 days in those with grade 2/3/4 rash (P = .0001). Similar findings have been made with cetuximab (Erbitux) and in some settings with gefitinib (Iressa). The strong association of rash severity with response/survival suggests that rash may serve as a marker of response to erlotinib treatment and may be used to guide treatment to obtain optimal response. Dosing erlotinib at the maximum tolerated dose, which is associated with more frequent and more severe rash, may improve response rates and survival durations. Further study of the potentially important association between rash and outcome of treatment with EGFR-targeted agents is needed.