SUMMARY: The American Cancer Society estimates that for 2024, about 100,640 new cases of melanoma of the skin will be diagnosed in the United States and 8,290 people are expected to die of the disease. The rates of melanoma have been rising rapidly over the past few decades, but this has varied by age. Surgical resection with a curative intent is the standard of care for patients with early-stage melanoma.
Patients with resected Stage IIB/C disease comprise a significant group of patients at significant risk of recurrence. Patients with Stage IIB disease have primary tumors that are more than 2 mm, and 4 mm or less in thickness, with ulceration (T3b), or more than 4 mm in thickness without ulceration (T4a). Patients with Stage IIC disease have primary tumors more than 4 mm in thickness with ulceration (T4b). Although Stage II melanoma is less advanced than Stage III, the 5-year risk of recurrence in patients with Stage IIB or Stage IIC disease without adjuvant therapy is approximately 35% and 50% respectively. The 5-year Melanoma-Specific Survival (MSS) rates for patients with Stage IIB/IIC disease are similar to those for Stage IIIA, Stage IIIB and Stage IIIC disease.
The Mitogen-Activated Protein Kinase pathway (MAPK pathway) is an important signaling pathway which enables the cell to respond to external stimuli. This pathway plays a dual role, regulating cytokine production and participating in cytokine dependent signaling cascade. The MAPK pathway of interest is the RAS-RAF-MEK-ERK pathway. The RAF family of kinases includes ARAF, BRAF and CRAF signaling molecules. BRAF is a very important intermediary of the RAS-RAF-MEK-ERK pathway. BRAF mutations have been demonstrated in 6-8% of all malignancies. The most common BRAF mutation in melanoma is at the V600E/K site and is detected in approximately 50% of melanomas, and result in constitutive activation of the MAPK pathway.
TAFINLAR® (Dabrafenib) is a selective oral BRAF inhibitor and MEKINIST® (Trametinib) is a potent and selective inhibitor of MEK gene, which is downstream from RAF in the MAPK pathway. In patients with BRAF V600 mutation-positive unresectable or metastatic melanoma, a combination of TAFINLAR® and MEKINIST® resulted in a median Overall Survival (OS) of more than 2 years, with approximately 20% of the patients remaining progression free at 3 years. These encouraging results led to the study of this combination in patients with Stage III melanoma, with BRAF V600E or V600K mutations, after complete surgical resection.
COMBI-AD, an international, multi-center, randomized, double-blind, placebo-controlled, Phase III trial, in which 870 patients with completely resected Stage III melanoma, and with BRAF V600E or V600K mutations were enrolled. Patients were randomly assigned in a 1:1 to receive TAFINLAR® 150 mg orally twice daily in combination with MEKINIST® 2 mg orally once daily (N=438) or two matched placebos (N=432). Treatment was given for 12 months. Eligible patients had undergone completion lymphadenectomy, with no clinical or radiographic evidence of residual regional node disease. None of the patients had received previous systemic anticancer treatment or radiotherapy for melanoma. BRAF V600 mutation status was confirmed in primary tumor tissue or lymph node tissue by a central reference laboratory. The median age was 50 years. Both treatment groups were well balanced and 18% had Stage IIIA disease, 41% had Stage IIIB disease, and 40% had Stage IIIC disease. Of the enrolled patients, 91% had a BRAF V600E mutation, and 9% had a BRAF V600K mutation. The Primary end point was Relapse Free Survival (RFS) and Secondary end points included Overall Survival (OS), Distant Metastasis-Free Survival, Freedom from relapse, and Safety.
The authors had previously reported the results for RFS and Distant Metastasis-Free Survival at 5 years of follow up. Overall survival was not analyzed as the data was not mature. The minimum duration of follow up was 59 months. The RFS at 5 years was 52% with TAFINLAR® plus MEKINIST® and 36% with placebo (HR for relapse or death=0.51). The Distant Metastasis-Free Survival at 5 years was 65% with TAFINLAR® plus MEKINIST® and 54% with placebo (HR for distant metastasis or death=0.55). As has been reported in previous studies, majority of relapses occurred within the first 3 years after surgery.
The researchers herein reported the final results of the COMBI-AD trial after a long-term follow-up of more than 8 years. The RFS continued to favor TAFINLAR® plus MEKINIST® over placebo. The median RFS was 93.1 months with TAFINLAR® plus MEKINIST® and 16.6 months with placebo (HR for relapse or death= 0.52). The estimated RFS at 10 years was 48% with TAFINLAR® plus MEKINIST® and 32% with placebo. A relapse with distant metastasis occurred in 28% of patients in the combination-therapy group and in 37% of patients in the placebo group (HR for distant metastasis or death=0.56). The estimated Distant Metastasis-Free Survival at 10 years was 63% and 48%, respectively. The estimated Overall Survival at 8 years was 71% with TAFINLAR® plus MEKINIST® and 65% with placebo (HR for death=0.80; P=0.06). However, this benefit was not statistically significant. A consistent survival benefit was seen across several prespecified subgroups, including those with BRAF V600E mutated tumors (HR for death=0.75). There was no new safety signals noted.
It was concluded that after nearly 10 years of follow-up, 12 months of adjuvant therapy with a combination of TAFINLAR® plus MEKINIST® resulted in longer Relapse Free and Distant metastasis-free Survival, compared to placebo, among patients with resected Stage III melanoma, with 25% reduction in the risk of death among those with BRAF V600E mutations.
Final Results for Adjuvant Dabrafenib plus Trametinib in Stage III Melanoma. Long GV, Hauschild A, Santinami M, et al. N Engl J Med 2024;391:1709-1720.
