Normal Tissue Exposure During Retroperitoneal Radiotherapy For Pure Seminoma Of The Testis.

334 Background: Emerging data suggest risk of cardiovascular disease following radiotherapy to the retroperitoneal nodes in stage I/II seminoma patients. This study quantifies radiation dose to organs contributing to cardiovascular disease.Organs at risk (OAR) were contoured using Eclipse. OARs consisted of the cardiac ventricles, kidneys, abdominal aorta, renal arteries, common iliac arteries, and external iliac arteries. Four dose-volume histograms corresponding to 4 treatment plans were generated for each patient. Each patient was planned as if being treated for a left primary seminoma. Plans 1/2 consisted of a standard PA strip field, while plans 3/4 consisted of a standard extended-field configuration. Field width for plans 1/3 spanned the transverse processes, while plans 2/4 included treatment of the left renal hilum. OAR doses were cumulatively reported for all 22.Median doses to the left kidney for plans 1, 2, 3 and 4 were 1.2, 2.2, 1.3 and 2.7 Gy, respectively. The median dose in treatment plan 2 was 1.0 Gy higher than plan 1, and in plan 4 it was 1.4 Gy higher than plan 3; suggesting increased left kidney dose when the renal hilum was included. The maximum distance between the top of the treatment field and the inferior ventricle was 7.1 cm, while the maximum ventricular-field overlap measured 1.81 cm. There were 4 of 22 patients (18%) who had overlap with 16.7 to 46.44 cm(3) of contoured ventricle within the field. The dose received by the cardiac ventricles ranged from 0-26.5 Gy, with the maximum dose of 26.5 Gy received by the patient with the greatest amount of overlap (1.81 cm).Adjusting treatment fields to include the renal hilum results in a higher dose to the kidneys and a mild increase in dose to the heart. While most patients have good separation of the heart and treatment field with extremely low cardiac doses, those whose ventricles are in field experience potentially significant cardiac doses. Our data suggests that for those patients with less than 2 cm between the superior portion of the treatment field and the inferior ventricle, the dose to the ventricles is at or approaches prescription dose. Clinicians treating seminoma patients may wish to consider this when determining candidacy for RT.