Total Body Irradiation, Etoposide, Cyclophosphamide and Autologous Peripheral Blood Stem Cell Transplantation Followed by Randomization to Therapy with Interleukin-2 Versus Observation for Patients with Non-Hodgkin’s Lymphoma: Results of a Phase III Randomized Trial by the Southwest Oncology Group (SWOG 9438).

Purpose: To determine the effect of post-transplant immunotherapy with Interleukin-2 (IL-2) on the progression-free and overall survival of patients with non-Hodgkin’s lymphoma (NHL) after autologous stem cell transplantation and to assess the toxicity of post-transplant IL-2 therapy.

Patients and Methods: Patients with previously treated low, intermediate, or high grade NHL (except Working Formulation Groups A and I) were treated with high-dose cyclophosphamide, etoposide, and total body irradiation (TBI) and an autologous peripheral blood stem cell transplant (PBSCT). Twenty-eight to 80 days after PBSCT, patients were randomized to treatment with IL-2 versus observation.

Results: Between January 1995 and July 2004, three hundred ninety-four patients with low-grade (n=61) or intermediate-high grade NHL (n=315) were registered at one of 39 SWOG transplant centers. One hundred ninety patients did not proceed to randomization, because of patient refusal (44), grade V toxicity (30), disease progression (28), toxicity (28), or other reasons. Two hundred four patients were randomized to treatment with continuous infusion intravenous IL-2 (9 ×10⁶ units/m²/day for four days followed five days later by 1.6 ×10⁶ units/m²/day for 10 days) versus observation. The 4-year progression-free survival estimate for all eligible patients is 34%, and the 4-year overall survival estimate is 52%. There was no difference in progression-free survival (hazard ratio (HR) of IL-2 to observation = 0.90; p = 0.56) nor in overall survival (HR of IL-2 to observation = 0.88; p = 0.55). There were no deaths related to IL-2 treatment. Grade IV IL-2-related toxicities included hematologic (n=10), cardiovascular (4), renal/bladder (2), flu-like symptoms (1), lung (1), metabolic (1), and neurologic (1) and were reversible in all cases.

Conclusions: These results confirm earlier SWOG findings that a regimen of cylophosphamide, etoposide and TBI followed by PBSCT can be administered to patients with relapsed or refractory NHL with acceptable toxicity and with encouraging progression-free and overall survival. Post-transplant therapy with IL-2 given at this dose and schedule of administration had no significant effect on post-transplant relapse, progression-free survival or overall survival.