• Stephen Johnston, Maureen Trudeau, Bella Kaufman, Hamouda Boussen, Kimberley Blackwell, Patricia LoRusso, Donald P Lombardi, Ben AhmedSlimS, Dennis L Citrin, Michelle L DeSilvio, Jennifer Harris, Ron E Westlund, Vanessa Salazar, Tal Z Zaks, and Neil L Spector.
• Department of Medicine-Breast Unit, Royal Marsden Hospital, London, United Kingdom.
• J. Clin. Oncol. 2008 Mar 1; 26 (7): 1066-72.

PurposeInflammatory breast cancer (IBC) is one of the most aggressive forms of breast cancer. Lapatinib, an oral reversible inhibitor of epidermal growth factor receptor (EGFR) and human EGFR 2 (HER-2), demonstrated clinical activity in four of five IBC patients in phase I trials. We conducted a phase II trial to confirm the sensitivity of IBC to lapatinib, to determine whether response is HER-2 or EGFR dependent, and to elucidate a molecular signature predictive of lapatinib sensitivity.Patients And MethodsOur open-label multicenter phase II trial (EGF103009) assessed clinical activity and safety of lapatinib monotherapy in patients with recurrent or anthracycline-refractory IBC. Patients were assigned to cohorts A (HER-2-overexpressing [HER-2+]) or B(HER-2-/EGFR+) and fresh pretreatment tumor biopsies were collected.ResultsForty-five patients (30 in cohort A; 15 in cohort B) received lapatinib 1,500 mg once daily continuously. Clinical presentation and biomarker analyses demonstrated a tumor molecular signature consistent with IBC. Lapatinib was generally well tolerated, with primarily grade 1/2 skin and GI toxicities. Fifteen patients (50%) in cohort A had clinical responses to lapatinib in skin and/or measurable disease (according to Response Evaluation Criteria in Solid Tumors) compared with one patient in cohort B. Within cohort A, phosphorylated (p) HER-3 and lack of p53 expression predicted for response to lapatinib (P < .05). Tumors coexpressing pHER-2 and pHER-3 were more likely to respond to lapatinib (nine of 10 v four of 14; P = .0045). Prior trastuzumab therapy and loss of phosphate and tensin homolog 10 (PTEN) did not preclude response to lapatinib.ConclusionLapatinib is well tolerated with clinical activity in heavily pretreated HER-2+, but not EGFR+/HER-2-, IBC. In this study, coexpression of pHER-2 and pHER-3 in tumors seems to predict for a favorable response to lapatinib. These findings warrant further investigation of lapatinib monotherapy or combination therapy in HER-2+ IBC.

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