Adjuvant immunotherapy of melanoma and development of new approaches using the neoadjuvant approach

Melanoma is the third most common skin cancer but the leading cause of death from cutaneous malignancies. Although early-stage disease is frequently cured by surgical resection with excellent long-term survival, patients with deeper primary lesions (AJCC stage IIB-C) and those with microscopic (IIIA) or clinically evident regional lymph node or in-transit metastases (IIIB-C) have an increased risk of relapse and death, the latter approaching 70% or more at 5 years. In patients at high risk of recurrence/metastases, adjuvant therapy with high-dose interferon alpha-2b (HDI) following definitive surgical resection has been shown to improve relapse-free and overall survival. Neoadjuvant chemotherapy and/or radiotherapy have offered the prospect to improve regional recurrence risk and overall survival in several solid tumors. The advent of effective new molecularly targeted therapies for metastatic disease and new immunotherapies that overcome checkpoints of immune response have augmented the range of new options that are in current trial evaluation to determine their role as potential adjuvant therapies, alone and in combination with one another, and the established modality of IFN-α. The differential characteristics of the host immune response between early and advanced melanoma provide a strong mechanistic rationale for the use of neoadjuvant immunotherapeutic approaches in melanoma, and the opportunity to evaluate the mechanism of action suggest neoadjuvant trial evaluation for each of the new candidate agents and combinations of interest. Several neoadjuvant trials have been conducted in the phase II setting, which have illuminated the mechanism of IFN-α, as well as providing insight to the effects of anti-CTLA4 blocking antibodies. These agents (anti-CTLA4 blocking antibody ipilimumab, and BRAF inhibitor vemurafenib) are likely to be followed by other immunotherapies that may overcome the PD-1 checkpoint (anti-PD1 and anti-PDL-1) as well as other molecularly targeted agents such as the BRAF inhibitor dabrafenib and the MEK inhibitors trametinib, selumetinib, and MEK162 in the near future. Evaluation of the clinical role of these agents as adjuvant therapy will take years to accomplish to ascertain the relapse-free survival benefits and overall survival benefits of these agents, but neoadjuvant exploration may provide early critical evidence of the therapeutic benefits, as well as clarifying the mechanisms of these agents alone and in combination.

IFN-α in the treatment of melanoma

Among the IFNs, IFN-α2 has been the most broadly evaluated clinically. At the molecular level, IFN-α has multiple effects in a variety of malignancies that range from antiangiogenic to potent immunoregulatory, differentiation-inducing, antiproliferative, and proapoptotic effects. A multitude of IFN-α2 regimens that may be classified as low dose, intermediate dose, and high dose have been evaluated as adjuvant therapy in melanoma. A durable impact on both relapse-free and overall survival was seen only with the regimen utilizing high-dose IFN-α2b tested in the Eastern Cooperative Oncology Group and intergroup trials E1684, E1690, and E1694 as adjuvant therapy for high-risk surgically resected melanoma (stage IIB or III). Adjuvant pegylated IFN-α2b has also been evaluated at maximally tolerable doses compared with the observation group in the European Organization for Research and Treatment of Cancer trial 18991 and has shown relapse-free survival benefits in patients with microscopic nodal disease.

Adjuvant therapy: melanoma

With an incidence that is increasing at 2–5% per year, cutaneous melanoma is an international scourge that disproportionately targets young individuals. Despite much research, the treatment of advanced disease is still quite challenging. Immunotherapy with high-dose interferon-α2b or interleukin-2 benefits a select group of patients in the adjuvant and metastatic settings, respectively, with significant attendant toxicity. Advances in the biology of malignant melanoma and the role of immunomodulatory therapy have produced advances that have stunned the field. In this paper, we review the data for the use of interferon-α2b in various dosing ranges, vaccine therapy, and the role of radiotherapy in the adjuvant setting for malignant melanoma. Recent trials in the metastatic setting using anticytoxic T-lymphocyte antigen-4 (anti-CTLA-4) monoclonal antibody therapy and BRAF inhibitor therapy have demonstrated clear benefit with prolongation of survival. Trials investigating combinations of these novel agents with existing immunomodulators are at present underway.

Ipilimumab: a novel immunostimulatory monoclonal antibody for the treatment of cancer

Ipilimumab (Yervoy, developed by Medarex and Bristol-Myers Squibb) is a fully human monoclonal IgG1κ antibody against the cytotoxic T-lymphocyte antigen-4 (CTLA-4), an immune-inhibitory molecule expressed in activated T cells and in suppressor T regulatory cells. Interaction of the monoclonal antibody with CTLA-4 blocks inhibitory signals generated through this receptor and enhances T cell activation, leading to increased antitumor responses. Ipilimumab has been approved by FDA in March 2011 as monotherapy (3mg/kg every 3 weeks for 4 doses) for the treatment of advanced (unresectable or metastatic) melanoma both in pre-treated or chemotherapy naïve patients. Four months later, ipilimumab has received a rapid approval by the European Commission, after a positive opinion from the Committee for Medicinal Products for Human Use. However, the indication in the EU is limited to previously-treated patients with advanced melanoma. Ipilimumab is the first agent that has demonstrated to improve overall survival in patients with metastatic melanoma, which has a very poor prognosis, in randomized phase III clinical trials. The patterns of tumour response to ipilimumab differ from those observed with cytotoxic chemotherapeutic agents, since patients may have a delayed yet durable response and obtain long-term survival benefit despite an initial tumour growth. The major draw-back of ipilimumab is the induction of immune-related adverse effects; the latter can be life-threatening, unless promptly managed with immunosuppressive agents (most frequently corticosteroids) according to specific guidelines. Further development of ipilimumab includes its use in the neoadjuvant or adjuvant high-risk melanoma setting and for the treatment of other refractory and advanced solid tumours, either as single agent or in combination with additional immunostimulating agents or molecularly targeted therapies.