The effect of radiotherapy treatment changes on sites of relapse in stage I testicular seminoma

AIM: To evaluate relapse patterns in stage I testicular seminoma related to changes in radiotherapy practice. METHOD: Four hundred and six patients with stage I testicular seminoma were treated with adjuvant radiotherapy following orchidectomy: 338 patients received para-aortic radiotherapy only and 68 patients with added risk factors had radiotherapy extended to include the pelvis. Computed tomograms of relapsed patients were reviewed and sites of relapse were documented with correlation to the radiotherapy field. RESULTS: Thirteen relapses were identified; 10 occurring in the para-aortic radiotherapy group (3.0% relapse rate) and three in the extended radiotherapy field group (4.4% relapse rate). Sites of relapse were; five pelvis, three mediastinum, one lung, one scapula, one scrotum, while one patient had multiple relapse sites including the pelvis and one had a tumour marker relapse with no site identified. All the pelvic relapses occurred in the para-aortic radiotherapy group. CONCLUSION: Pelvic relapse only occurred when radiotherapy had been confined to the para-aortic region. Since para-aortic radiotherapy achieves equivalent outcome to wider field radiotherapy with reduced toxicity, it is likely to become standard practice in stage I seminoma and pelvic relapses will therefore increase in frequency. It is therefore important to include pelvic imaging when relapse is suspected.