Interleukin-2-induced splenic enlargement

Splenomegaly in patients with cancer raises the suspicion of tumor involvement. Splenic enlargement in the absence of splenic metastases, however, has been reported in patients treated with interleukin-2 (IL-2) immunotherapy. This study characterizes the change in spleen size that occurred in 42 patients treated with IL-2 between 1989 and 1993 for nonhematologic malignancies. Computed tomography (CT) scans before and during immunotherapy were available for review on all 42 patients and after immunotherapy on 16 of these patients. The splenic index was measured for each CT by a single reader blinded to the time course of IL-2 therapy. Mean splenic index increased 64.1% from 646 cm3 (standard deviation [SD], 387) pre-IL-2 to 1059 cm3 (SD, 534) during therapy with IL-2 (P < 0.0001). The splenic index remained elevated at 1112 cm3 (SD, 633) after completion of IL-2 therapy. Splenomegaly, temporally associated with IL-2 therapy for nonhematologic malignancies, is likely to represent a sequela of therapy and not tumor progression.