4530 Background: Radiotherapy (RT) is considered the standard treatment for stages IIA/B testicular seminoma. However, RT has been associated with an increased incidence of second malignancies in long-term survivors. As chemotherapy (CT) is highly effective in advanced disease and in recurrences after RT, we have developed a multicenter prospective protocol of treatment with CT in patients (pts) with stages IIA/B seminoma. Methods: We studied 71 consecutive pts with stages IIA and IIB testicular seminoma, initially treated with cisplatin-based chemotherapy, from April 1994 to March 2003 in 26 centers. 34 of these pts were previously reported within a wider series of pts with stages II-IV seminoma (Ann Oncol 2001;12:487). Patient characteristics were: median age 38 (27–84) years; 18 pts had stage IIA and 53 had stage IIB; 11 of these pts had had a relapse of a previous stage I on surveillance; 8 pts had high BHCG levels. The treatment administered was: EP (etoposide, cisplatin) in 62 and BEP (bleomycin, etoposide, cisplatin) in 9 pts. The number of cycles per patient was: 3 (9 pts), 4 (58), >4 (4). Results: There were 59 (83%) complete responses and 12 (17%) partial responses with residual mass and normal markers. 2 pts underwent resection of residual masses. After a median follow-up of 46 months, 6 pts relapsed and one of them died. Progression-free survival and overall survival at 4 years were 91% (95%CI: 83%–98%) and 98% (95%CI: 89%–100%), respectively. Hematological toxicity was: Granulocytopenia G-IV:1 pts, G-III: 3, G-II: 6; Thrombocytopenia G-III:2, G-II:2; Anemia G-III:1, G-II:1; Extrahematological toxicity was: Nausea/Vomiting G-III:6, G-II:16, Stomatitis GIII: 1, G-II: 3, Diarrhea G-III:1; Pulmonary toxicity G-III:1; Neurotoxicity G-II:4; Skin rash G-II:1. No significant late toxicity was observed. Conclusions: CT for stages IIA/B seminoma provides excellent results, is well tolerated and avoids the serious late morbidity associated with RT. Our results support the role of CT as an alternative to RT in the treatment of these pts. Comparison with RT focusing on long-term toxicities would be of great interest. No significant financial relationships to disclose.