Therapeutic Implications of Detecting MAPK-Activating Alterations in Cutaneous and Unknown Primary Melanomas

Abstract

Purpose: Cutaneous and unknown primary melanomas frequently harbor alterations that activate the Mitogen Activated Protein Kinase (MAPK) pathway. Whether MAPK driver detection beyond BRAF V600 is clinically relevant in the checkpoint inhibitor era is unknown.Methods:Patients with melanoma were prospectivelyofferedtumor sequencingof 341-468 genes. Oncogenic alterations in 28 RTK-RAS-MAPK pathway genes were used to construct MAPK driver groups. Time to treatment failure(TTF)was determinedfor patients who received frontline PD-1 monotherapy,nivolumab plus ipilimumab,or subsequentgenomically matched targeted therapies.A Cox proportional hazards model was constructed for TTF using driver group and clinical variables.Results:670 of 696 sequenced melanomas (96%) harbored an oncogenic RTK-RAS-MAPK pathway alteration; 33% had {greater than or equal to}1 driver. Nine driver groups varied by clinical presentation and mutational burden. TTF of PD-1 monotherapy (N=181) varied by driver, with worse outcomes for NRAS Q61 and BRAF V600 versus NF1 or other alterations (median 4.2, 7.5, 22 and not reached;p<0.0001). Driver group remained significant independent of TMB and clinical features. TTF did not vary by driver for nivolumab plus ipilimumab (N=141). Among 172 patients with BRAF V600 wild-type melanoma who progressed on checkpoint blockade, 27 were treated with genomically matched therapy, and 8 (30%) derived clinical benefit lasting {greater than or equal to}6 months. Conclusion: Targeted capture multigene sequencingcan detect oncogenicRTK-RAS-MAPK pathway alterations in almost allcutaneous and unknown primary melanomas. Time to treatment failure of PD-1 monotherapy varies by mechanism of ERK activation.Oncogenic kinase fusionscan be successfully targetedin immune checkpointinhibitor-refractory melanoma.