For patients with BRAF V600–mutation positive melanoma who progress on front-line molecularly targeted therapy, immune checkpoint inhibitor therapy with either anti-PD-1 monotherapy or combination anti-PD-1 and ipilimumab should be considered. The KEYNOTE-006 trial that demonstrated superiority of pembrolizumab compared to ipilimumab included patients who had received up to 1 prior systemic therapy that was not a PD-1 or CTLA-4 inhibitor, and subgroup analysis demonstrated efficacy with pembrolizumab in patients who had received prior treatment with a BRAF inhibitor.9 The retrospective analysis by Tétu et al (Table 1) noted efficacy of combination nivolumab and ipilimumab in patients treated with prior molecularly targeted therapy, as evidenced by an ORR of 35% and median OS of 16.5 months.8
A retrospective trial by Ackerman et al analyzed ORR, median PFS, and median OS from the time of commencement of BRAF inhibitor therapy (with or without a MEK inhibitor), and the comparison was made between those who received ipilimumab before or after molecularly targeted therapy. While ipilimumab is no longer the first-line immunotherapy agent used in advanced melanoma, the study did highlight some important concepts. First, ORRs to BRAF inhibitors were similar between the 2 treatment groups. The conclusions of the analysis were that there was no significant difference in median PFS or OS in regard to which therapy was given first, but median OS after BRAF inhibitors were discontinued was very short and patients had poor responses to ipilimumab after stopping a BRAF inhibitor. This highlights the concern that patients who have progressive disease on molecularly targeted therapy often have a poor performance status and undergo too rapid of a clinical decline to derive benefit from immunotherapy, which can often take weeks to months to take effect.10
A more recent retrospective study by Johnson et al compared efficacy outcomes in patients who received single-agent anti-PD-1 therapy prior to molecularly targeted therapy (BRAF inhibitor with or without MEK inhibitor) to those who received molecularly targeted therapy prior to anti-PD-1 therapy. The difference in median OS was not statistically significant (27.5 months with PD-1 inhibitor first vs 40.3 months with molecularly targeted therapy first). Both treatments demonstrated second-line efficacy, but outcomes were inferior to those reported when either type of therapy was used in the first-line setting. Interestingly, patients who were maintained on molecularly targeted therapy for more than 6 months prior to progression demonstrated an improved ORR to subsequent anti-PD-1 therapy (34% vs 15%).11
Molecularly Targeted Therapy in Progressive Disease
When melanoma patients with a BRAF V600 mutation are treated initially with immunotherapy and demonstrate progressive disease, molecularly targeted therapy with combined BRAF and MEK inhibition should be considered for second-line therapy. While there are no dedicated prospective trial results with BRAF/MEK inhibitors after progression on immune checkpoint inhibitors, for practical purposes, it may be reasonable to extrapolate outcomes from the currently available first-line studies.12-16 An ongoing study (NCT02224781) in which patients are randomized to receive ipilimumab/nivolumab followed by dabrafenib/trametinib at progression versus the reverse order is designed to help answer the question of optimal sequencing and timing of therapy. Johnson et al’s retrospective analysis of patients receiving single-agent anti-PD-1 therapy prior to molecularly targeted therapy compared to the reverse order concluded that there was no statistically significant difference in median OS.11 Ackerman et al’s retrospective study of patients who had received ipilimumab before or after molecularly targeted therapy noted similar response rates to molecularly targeted therapy in each treatment group.10
The issue of re-treatment with a BRAF/MEK inhibitor in a patient already progressing on targeted therapy is a more challenging situation, and currently available data suggests there is limited benefit. However, select patients may be considered for this approach. The combination of dabrafenib/trametinib demonstrated an ORR of approximately 15% in a cohort of patients who progressed on single-agent BRAF inhibitor therapy, with a suggestion that those patients who had previously derived benefit for more than 6 months may have a more favorable outcome.17