Testicular seminoma: Scattered radiation dose to the contralateral testis in the modern era.

ABSTRACT

PURPOSE: Limited data exist on testicular dose measurements using modern radiation treatment techniques and volumes for testicular seminoma. The aim of this study was to report the testicular dose using in vivo measurements in men with testicular seminoma receiving abdominopelvic radiation therapy (APRT) and a modified dog-leg field with and without gonadal shielding. METHODS AND MATERIALS Men with histologically confirmed testicular seminoma, either newly diagnosed stage II disease or isolated retroperitoneal relapse on surveillance for stage I disease, treated with APRT had testicular dose measurements recorded using MOSFET dosimeters. Those patients wishing to preserve fertility underwent radiation treatment with daily gonadal shielding. Factors that may influence testicular dose including field size, distance of the remaining testis from the radiation field, and patient separation, were also measured. RESULTS: Measurements were performed for 16 men; 10 with gonadal shielding and 6 without. The mean measured dose to the testis in the patients with gonadal shielding was 2.6 cGy (standard error, 0.75; range, 0-13) compared with 28.6 cGy (standard error, 12.6; range, 0-86) in the unshielded group for a 20-fraction treatment. CONCLUSIONS: The use of gonadal shielding during APRT with a modified dog-leg technique results in a low testicular dose that is below the likely threshold for impaired spermatogenesis. In those men wishing to preserve fertility, we recommend the use of gonadal shielding, even with the use of modern radiation therapy techniques.