Updated 5-y landmark analyses of phase 2 (BREAK-2) and phase 3 (BREAK-3) studies evaluating dabrafenib monotherapy in patients with BRAF V600–mutant melanoma.

9526 Background: Prior analyses of phase 2 (BREAK-2; NCT01153763) and phase 3 (BREAK-3; NCT01227889) trials showed that durable clinical benefit and tolerability lasting ≥ 3 y are achievable with the BRAF inhibitor dabrafenib in some patients (pts) with BRAFV600–mutant metastatic melanoma. Here, we report 5-y landmark analyses for BREAK-2 and BREAK-3. Methods: BREAK-2, a single-arm, phase 2 study, evaluated dabrafenib 150 mg twice daily in pts with stage IV BRAF V600E/K–mutant MM. BREAK-3, an open-label, randomized (3:1), phase 3 study, assessed dabrafenib 150 mg twice daily vs dacarbazine 1000 mg/m 2 every 3 weeks in pts with previously untreated BRAFV600E–mutant unresectable stage III or stage IV MM. Updated analyses were performed to describe ≥ 5-y outcomes in each study. Results: BREAK-2 enrolled 92 pts (V600E, n = 76; V600K, n = 16), of whom most (90%) had prior systemic anticancer therapy. At data cutoff (17 Jun 2016), all pts had discontinued, mostly due to progression (84%). In V600E pts, 5-y progression-free survival (PFS) was 11%, and 5-y overall survival (OS) was 20%. Postprogression immunotherapy was received by 22% of enrolled pts. In BREAK-3 (data cutoff, 16 Sep 2016), median follow-up was 18.6 mo for the dabrafenib arm (n = 187) and 12.8 mo for the dacarbazine arm (n = 63). Follow-up for the 37 dacarbazine-arm pts (59%) who crossed over to receive dabrafenib was based on the initial assignment of dacarbazine. The 5-y PFS was 12% vs 3% and 5-y OS was 24% vs 22% for the dabrafenib and dacarbazine arms, respectively. A subset of pts in each respective arm received postprogression anti–CTLA-4 (24% vs 24%) and/or anti–PD-1 (8% vs 2%) therapy, whereas 31% vs 17% did not receive any further therapy following study treatment. No new safety signals were observed in either study with long-term follow-up. Additional characterization of pts using cfDNA analysis will be presented. Conclusions: These data provide the longest reported PFS and OS follow-up for BRAF inhibitor monotherapy in BRAF V600–mutant MM. Both BREAK-2 and BREAK-3 showed that 11%-12% of pts initially treated with single-agent dabrafenib remained progression free at 5 y. Clinical trial information: NCT01153763; NCT01227889.