Purpose: To analyze the long-term results with radiotherapy (RT) for early-stage, low-grade follicular lymphomas.
Methods and materials: From 1960 to 1988, 80 patients with Stage I (n = 33) or II (n = 47), World Health Organization Grade 1 (n = 50) or 2 (n = 30) follicular lymphoma were treated with RT. The lymph nodes or spleen were involved in 97% of cases. The maximal tumor sizes ranged from 0.5 to 11.0 cm (median 2.0). The RT fields encompassed only the involved Ann Arbor nodal region (involved-field RT) in 9% of the patients. The fields also included 1-3 adjacent, grossly uninvolved nodal regions (regional RT) in 54% of patients but were smaller than mantle or whole abdominopelvic fields. Mantle or whole abdominopelvic fields encompassing up to 6 grossly uninvolved regions (extended-field RT) were used in the remaining 37% of patients. The total RT doses ranged from 26.2 to 50.0 Gy given in daily 1.0-3.0-Gy fractions.
Results: The follow-up of the surviving patients ranged from 3.5 to 28.7 years (median 19.0). No recurrences were found >17.0 years after RT, with 13 patients free of disease at their last follow-up visit 17.6-25.0 years after treatment. In 58% of cases, death was not from follicular lymphoma. The 15-year local control rate was 100% for 44 lymphomas <3.0 cm treated with only 27.8-30.8 Gy (median 30.0 in 20 fractions). Progression-free survival was affected by the maximal tumor size at the start of RT (15-year rate 49% vs. 29% for lymphomas <3.0 cm vs. > or =3.0 cm, respectively, p = 0.04) and Ann Arbor stage (15-year rate 66% vs. 26% for Stages I and II, respectively, p = 0.006). Ann Arbor stage also affected the cause-specific survival (15-year rate 87% vs. 54% for Stages I and II, respectively, p = 0.01). No significant difference was found in overall survival between those treated with extended-field RT and those treated with involved-field RT or regional RT (15-year rate 49% and 40%, respectively, p = 0.51). The 15-year incidence rate of Grade 3 or greater late complications according to the Subjective, Objective, Management, and Analytical scale in patients treated with 26.2-30.8 Gy vs. 30.9-50.0 Gy was 0% and 6%, respectively.
Conclusions: RT can cure approximately one half of Stage I and one quarter of Stage II, World Health Organization Grade 1 or 2 follicular lymphomas. Follicular lymphomas <3.0 cm can be controlled locally with doses of 27.8-30.8 Gy, and there is a trend toward a higher incidence of late complications with doses of >30.8 Gy. Doses of 25-30 Gy delivered in 15-20 fractions should be examined prospectively in patients with follicular lymphomas of <3.0 cm.