Purpose
The goal of this work was to analyze the response rate and outcome of patients with stage I–III follicular lymphoma (FL) treated with radiotherapy (RT) alone.
Patients and methods
The records of 50 consecutive patients with stage I–III FL treated with RT alone at our department from 1988–2009 were analyzed. The median age was 60 years (range 32–80 years) with a median follow-up duration of 8 years (range 4–11 years). Clinical staging was performed according to the Ann Arbor system. Stage I: 30 patients (60%), stage II: 15 patients (30%), stage III: 5 patients (10%). Thirty-two patients (64%) presented with nodal disease, 14 patients (28%) presented with disease in extranodal sites, and 4 patients (8%) had nodal and extranodal involvement. The RT field encompassed only the involved Ann Arbor nodal regions (involved-field RT) in 26 patients (52%), mantle and whole abdominopelvic fields in 6 patients (12%), mantle field in 10 patients (20%), whole abdominopelvic fields in 5 patients (10%), and a so-called mini-mantle in 3 patients (6%). The total RT dose ranged from 26–56 Gy (median 40 Gy) in daily fractions of 1.2–2.5 Gy.
Results
Complete remission (CR) and partial remission (PR) were observed in 39 (76%) and 9 (20%) patients, respectively. Only 2 of 8 patients (25%) with tumor bulk > 5 cm reached CR, whereas 37 of 42 patients (88%) with a maximum lymphoma diameter < 5 cm achieved CR (p = 0.0001). The median overall survival (OS) and median event-free survival (EFS) were 18 years (CI 95% 10–26 years) and 7 years (6–8 years), respectively. The 2-, 5-, and 10-year OS were 96 ± 3%, 90 ± 5%, and 70 ± 9%, respectively. The 2-, 5-, and 10-year EFS were 90 ± 5%, 70 ± 7%, and 38 ± 9%, respectively. Fifteen patients developed a recurrence outside the radiation field (30%) and 4 patients developed an in-field recurrence (8%). All in-field recurrences were observed in regions without clinical (macroscopic) involvement, which were irradiated with a dose of ≤ 26 Gy. Pretreatment maximum lymphoma diameter < 5 cm (p = 0.039) and complete remission after RT (p = 0.021) were significantly associated with a better OS in the univariate analysis.
Conclusion
RT is a curative option in the treatment of limited stage FL. If RT of microscopically uninvolved area is necessary, a reduction in the radiation dose should be carefully weighed against the risk of in-field recurrences.