Long-term outcome in stage I and II follicular lymphoma following treatment with involved field radiation therapy alone

6521 Background: Patients with localized follicular lymphoma (FL) are usually treated with radiation therapy (RT). The aim of this study was to assess the long-term overall survival (OS), local disease control and pattern of relapse after involved-field RT in stage I/II FL Methods: 669 patients with stage I and II FL were seen between 1968 and 1999. The records on these patients were systematically collected in an institutional database. The analysis focused on the outcome of treatment in terms of OS, relapse and local disease control in those initially treated with involved-field RT alone (n=460). Median RT dose was 35 Gy (16.0 –47.5 Gy) given over 3–4 wks Results: In 460 patients treated with RT alone, the median age at diagnosis was 59 yrs (17 - 86 yrs); median follow-up duration was 12.5 yrs (range 1.1 –32.2 yrs). The clinical stage was: stage IA: 337 pts, stage IIA: 115 pts, IB: 2 pts and IIB: 5 pts. Histology was: follicular grade 1: 35%, grade 2: 38%, and grade 3: 27%. 75% had nodal disease alone, and 25% presented with extranodal disease. 43% had Karnofsky performance status (KPS) of 100% and 55% KPS of 90%. OS at 5 and 10 yrs were 79% and 62% and DFS 56% and 41%, respectively. Local disease control was excellent; 450 patients achieved complete response and only 5.5% relapsed in radiation fields. Most relapses occurred in distant sites. The cumulative incidence rates for relapse at 5, 10, 15, 20, and 25 yrs were 38%, 48%, 54%, 56%, and 56% respectively. For those at risk of relapse, the probability of relapse between 5 and 10 yrs was only 11%, for 10–15 yrs 6%, and beyond 15 yrs, 2%. Conclusions: Involved-field radiation therapy provides excellent local control in stage I and II follicular lymphomas. Long-term clinical disease control is observed in over 40% of pts. While 30% of all relapses occur after 5 years, risk of very late relapse is low. Long-term follow-up is recommended. No significant financial relationships to disclose.