Treatment of cutaneous T cell lymphoma: Current status and future directions

The treatment of cutaneous T cell lymphoma (CTCL), which includes mycosis fungoides and Sezary syndrome, has been in a state of continual change over recent decades, as new therapies are constantly emerging in the search for more effective treatments for the disease. However, prognosis and survival of patients with CTCL remains dependent upon overall clinical stage (stage IA-IVB) at presentation, as well as response to therapy. Past therapies have been limited by toxicity or the lack of consistently durable responses, and few treatments have been shown to actually alter survival, especially in the late stages of disease. Even aggressive chemotherapy has not been shown to improve overall survival compared to conservative sequential therapy in advanced disease, and adds the risk of immunosuppressive complications. Over the last decade, extracorporeal photopheresis has been the only single treatment that has been shown to improve survival in patients with Sezary syndrome, although its true efficacy and place in combination therapy remain unclear. Much of the focus of current research has been on combinations of skin-directed therapies and biological response modifiers, which improve response rates. The results of various trials over the years have also brought into favor the use of post-remission maintenance therapy with topical corticosteroids, topical mechlorethamine (nitrogen mustard), interferon-α, or phototherapy to prevent disease relapse. Recent novel developments in CTCL therapy include oral bexarotene, a retinoid X receptor-selective retinoid that has activity in all stages of CTCL, and the topical gel formulation of bexarotene, which plays a role in treating localized lesions. US Food and Drug Administration (FDA)-approved, oral systemic bexarotene has the advantage of a 48% overall response rate at a dosage of 300 mg/m2/day, and avoids immunosuppression and risk of central line and catheter-related infectious complications that are associated with other systemic therapies. Monitoring of triglycerides and use of concomitant lipid-lowering agents and thyroid replacement is required in most patients. Also recently FDA-approved, denileukin diftitox is the first of a novel class of fusion toxin proteins and is selective for interleukin-2R (CD25+) T cells, targeting the malignant T cell clones in CTCL. Denileukin diftitox is associated with capillary leak syndrome in 20 to 30% of patients, which may be ameliorated by hydration and corticosteroids. Higher response rates are possible by combining bexarotene with 'statin' drugs and active CTCL therapies. Studies are being conducted on combining bexarotene and denileukin diftitox with other modalities. Biological response modifier therapies that are in current or future investigational trials include topical tazarotene, pegylated interferon, interleukin-2, and interleukin-12. At the forefront of systemic chemotherapy development, pegylated liposomal doxorubicin, gemcitabine, and pentostatin appear to have the greatest potential for success in CTCL therapy. Bone marrow transplantation, which is currently limited by the risk of graft-versus-host disease, offers the greatest potential for disease cure. Further developments for CTCL may include more selective immunomodulatory agents, vaccines, and monoclonal antibodies.