Rates of ERBB2 Alterations Across Melanoma Subtypes and a Complete Response to Trastuzumab Emtansine in an ERBB2-amplified Acral Melanoma

Purpose: Patients with BRAF V600-wild type melanoma whose tumors progress on checkpoint inhibition currently have limited therapeutic options, and additional rational treatment targets are needed. ERBB2 alterations may be amenable to targeted inhibition, but the rate of ERBB2 alterations across melanoma subtypes is not well described. Experimental Design: All patients with non-uveal melanoma (cutaneous, acral, mucosal, and unknown primary) whose tumors underwent multigene sequencing with MSK-IMPACT at Memorial Sloan Kettering Cancer Center from 2014-2018 were reviewed for known or likely oncogenic somatic alterations in ERBB2 and the other known canonical driver genes BRAF, NRAS, KIT, NF1, GNAQ, and GNA11. Results: A patient with acral melanoma resistant to checkpoint inhibition was found to have an ERBB2 amplification and achieved a durable complete response to trastuzumab emtansine. Tumor sequencing results from 732 melanoma cases were analyzed for ERBB2 and canonical driver gene alterations. ERBB2 amplifications were detected in acral (3%) and mucosal (3%) melanomas. ERBB2 mutations were found in cutaneous (1%), acral (2%), and mucosal (2%) subtypes and frequently co-occurred with NF1 alterations. Among the 140 patients whose tumors lacked canonical driver alterations, ERBB2 amplifications were detected in acral (7%) and mucosal (6%) melanoma. Conclusions: ERBB2 amplification is present in a minority of acral lentiginous and mucosal melanomas. Activating mutations in ERBB2 were identified in non-uveal melanoma subtypes and are frequently co-mutated with canonical drivers. HER2 could represent a therapeutically relevant target across melanoma subtypes.

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