A phase II trial of subcutaneously administered recombinant human interleukin-2 in patients with relapsed/refractory thymoma.

The thymus is the site of T-cell maturation and contains T-cell precursors that differentiate into cytolytic T lymphocytes (CTLs) in vitro in the presence of interleukin-2 (IL-2). Malignant thymoma is often associated with a lymphocytic infiltration of these precursors. The antitumor effects of IL-2 are mediated in part by activated CTLs. Based on these considerations and anecdotal reports of its anti-tumor activity in thymoma, we conducted a Phase II trial of IL-2 in 14 patients with thymoma. IL-2 was administered s.c. at a dose of 12 x 10(6) IU/m2/day for 5 days for 4 weeks followed by a 2-week rest period. Patients were evaluated for response after each 6-week cycle, and those tolerating therapy with no disease progression were eligible for a maximum of 4 cycles. All patients had failed prior standard chemotherapy and 12 had received prior radiotherapy. All 14 patients were evaluable for toxicity and response. The median number of cycles received was two. One patient was removed from study during cycle 1 because of severe bronchospasm. Five patients required dose reductions for grade 3 toxicity (anorexia, nausea, hyperbilirubinemia, elevated SGPT, and skin desquamation, one patient each). Two patients developed new symptoms of myasthenia gravis while in the study and were removed (one for progressive disease, one for steroid requirement). There were no objective responses. The one patient who required steroids for newly diagnosed myasthenia gravis had a minor response. We conclude that subcutaneously administered IL-2, although it has acceptable toxicity, has no significant clinical activity in previously treated patients with advanced thymoma.