131I-tositumomab myeloablative radioimmunotherapy for non-Hodgkin’s lymphoma

Abstract

To investigate radiation doses to the testes delivered by a radiolabeled anti-CD20 antibody and its effects on male sex hormone levels. Testicular uptake and retention of (131)I-tositumomab were measured, and testicular absorbed doses were calculated for 67 male patients (54 ± 11 years of age) with non-Hodgkin's lymphoma who had undergone myeloablative radioimmunotherapy (RIT) using (131)I-tositumomab. Time-activity curves for the major organs, testes, and whole body were generated from planar imaging studies. In a subset of patients, male sex hormones were measured before and 1 year after the therapy. The absorbed dose to the testes showed considerable variability (range = 4.4-70.2 Gy). Pretherapy levels of total testosterone were below the lower limit of the reference range, and post-therapy evaluation demonstrated further reduction [4.6 ± 1.8 nmol/l (pre-RIT) vs. 3.8 ± 2.9 nmol/l (post-RIT), P<0.05]. Patients receiving higher radiation doses to the testes (≥ 25 Gy) showed a greater reduction [4.7 ± 1.6 nmol/l (pre-RIT) vs. 3.3 ± 2.7 nmol/l (post-RIT), P<0.05] compared with patients receiving lower doses (<25 Gy), who showed no significant change in total testosterone levels. The testicular radiation absorbed dose varied highly among individual patients. Patients receiving higher doses to the testes were more likely to show post-RIT suppression of testosterone levels.