lnterleukin-2 ± Lymphocytes as Consolidative Immunotherapy after Autologous Bone Marrow Transplantation for Hematologic Malignancies

Patients who undergo autologous bone marrow transplantation (ABMT) for advanced hematologic malignancies experience a high relapse rate. Therapy with interleukin-2 (IL-2) +/- lymphokine-activated killer (LAK) cells has induced clinical responses in some patients with advanced malignant lymphoma (ML) or acute myelogenous leukemia (AML). It is postulated that IL-2 +/- LAK cells represents a potentially non-cross-resistant therapeutic modality which might prevent or delay relapses if used as consolidative immunotherapy after ABMT, at a time of minimal residual disease. Therefore, we first studied the reconstitution of IL-2-responsive LAK precursor cells after ABMT and found them in the circulation as early as 3 weeks after ABMT. A phase Ib clinical trial was then performed which identified a tolerable IL-2 regimen which could be administered early after ABMT and which could induce immunomodulatory effects. We then initiated a clinical trial to determine the feasibility of generating and administering autologous LAK cells using this IL-2 regimen after ABMT for 16 patients with ML. The results show that IL-2+LAK therapy early after ABMT is feasible but is more toxic than IL-2 alone. Patients with AML on the phase I IL-2 trial and with ML on the IL-2+LAK protocol were evaluated for tumor status. Of 8 patients with AML in first relapse or at a later stage who underwent ABMT and received IL-2, 2 have relapsed, while 6 remain in complete remission 26+ to 40+ (median 28+) months after ABMT. Of 16 patients with ML considered at high risk for relapse who were treated with ABMT+IL-2+LAK, 5 have relapsed, while 11 remain in complete remission at 6+ to 21+ (median 10+) months after ABMT. The results in both trials are quite encouraging and appear to be better than those in nonrandomized historical controls at our institution. Prospectively randomized trials of IL-2 versus no IL-2 after ABMT in such patients are being initiated to assess definitively the effect, if any, on the relapse rate.