Based on the hypothesis that acquired resistance to BRAF/MEK inhibition may be reversible if the selective pressure of the medication is held for a period of time, a phase 2 trial analyzed outcomes with retreatment. The study included patients with BRAF V600–mutant melanoma who had progressed on prior BRAF inhibition (with or without MEK inhibitor) and required that they had been off of therapy for at least 12 weeks. Of the 25 patients who received dabrafenib plus trametinib as retreatment, 32% demonstrated a partial response and 40% had stable disease.18 While further studies are warranted, retreatment with molecularly targeted therapy may be a viable option, especially in light of the multiple approved BRAF and MEK inhibitor combinations.
Another concept that has been studied is treatment beyond disease progression with molecularly targeted therapy. In a retrospective analysis of patients who had progressed on a single-agent BRAF inhibitor, 39% of those patients were continued on the same BRAF inhibitor and compared to patients who received no subsequent therapy or changed to an alternative systemic therapy. In the multivariable analysis adjusting for other prognostic factors, continued treatment with the BRAF inhibitor was associated with prolonged OS.19
Case Conclusion
The patient is started on second-line therapy with nivolumab and ipilimumab and demonstrates a partial response. One year later he continues to feel well with decreased size of the intracranial and right lower lobe lesions, and without any interval development of new areas of metastatic disease.
Special Considerations
Intralesional Therapies
Talimogene laherparepvec (T-VEC) is a genetically modified herpesvirus-1 oncolytic virus that is injected into melanoma skin lesions and leads to the expression of granulocyte-macrophage colony-stimulating factor. While T-VEC is currently approved for local treatment of unresectable cutaneous, subcutaneous, or nodal recurrences,20 it has also been investigated in combination with other therapies for patients with advanced disease. In patients with previously treated melanoma, T-VEC plus ipilimumab demonstrated superior ORR to ipilimumab alone (39% vs 18%), and the tumor response was not limited to the injected lesions. The observation of systemic response suggests synergy between T-VEC and immune checkpoint blockade in enhancing the anti-tumor immune response.21 The phase 1b MASTERKEY-265 trial combining pembrolizumab and T-VEC led to an ORR of 62% and CR of 33%.22 A phase 3 trial comparing pembrolizumab plus T-VEC to pembrolizumab alone is ongoing (NCT02263508).
Melanoma Brain Metastases
The presence of brain metastases is a common event in patients with metastatic melanoma, and often confers a poor prognosis.23 The approach to the management of brain metastases should be multidisciplinary among medical oncology, neurosurgery, and radiation oncology providers, as treatment algorithms continue to rapidly evolve. Historically, there has been little prospective clinical trial data regarding optimal systemic therapy, and local therapies such as surgery or stereotactic radiation have long been the mainstay of therapy for intracranial disease.24 However, recent data with both immunotherapy and molecularly targeted therapy has demonstrated efficacy with intracranial metastases.