Purpose: To investigate radiation doses to the testes delivered by a radiolabeled anti-CD20 antibody and its effects on male sex hormone levels.
Materials and methods: Testicular uptake and retention of 131I-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 131I-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.
Results: 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.
Conclusion: 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.
aDepartment of Radiology, Division of Nuclear Medicine, University of Washington
bFred Hutchinson Cancer Research Center, Seattle
cPacific Northwest National Laboratory, Richland, Washington, USA
Correspondence to Joseph G. Rajendran, MD, DMRT, FASNC, FACNM, Box 356113, RR 214A, University of Washington, Seattle, WA 98195, USA Tel: +1 206 616 5781; fax: +1 206 598 6406; e-mail: email@example.com
Received April 10, 2012
Accepted August 2, 2012