REACH: Study to Determine the Aetiology of Chlormethine Gel Induced-skin Drug Reaction in Early Stage Mycosis Fungoides Cutaneous T Cell Lymphoma (MF-CTCL)

Adult patients with early stage MF-CTCL (stage IA-IB) will be eligible for this study. A total of 100 early stage MF-CTCL patients diagnosed in the past year will be enrolled. Treatment with CL gel will be applied once daily to all skin areas affected by MF-CTCL and, for 8 weeks, one selected skin area unaffected by MF-CTCL (0.5% body surface area) until treatment response (complete response), study treatment duration completed (56 weeks), progression, or another withdrawal criterion is met. Depending on the type of skin drug-related reaction (if any) occurring after application of CL gel, this study will categorize patients into three different groups corresponding to three different treatment patterns: * Group A: Patients with no skin drug reaction with CL gel application * Group B: Patients developing a skin drug reaction of any grade with CL gel application, not due to allergic reaction to CL gel, will continue treatment at reduced application frequency * Group C: Patients from Group B unable to tolerate reduced CL gel application frequency will apply a potent topical steroid twice daily in addition to CL gel applied every other day