Effectiveness and tolerability of radiotherapy for patients with indolent non-Hodgkin's lymphoma - a monocenter analysis

Abstract Purpose To analyze the effectiveness and toxicities of radiotherapy in indolent non-Hodgkin's lymphoma (iNHL) patients treated in our institution. Material and Methods Patients with iNHL treated with radiotherapy between 1999 and 2016 were included. The primary endpoint was progression-free survival (PFS). Secondary endpoints were local control (LC), overall survival (OS) and toxicities. PFS, LC, and OS were analyzed using Kaplan-Meier method. Log-rank test was used to investigate the differences between subgroups. Cox proportional hazard model was used for univariate continuous analysis.Results Seventy-five patients were identified in our institutional database between 1999 and 2016. Fifty-eight (77.3%) had stage I after Ann-Arbor and 17 patients (22.7%) had stage II. The median follow-up was 87 months (95%-CI: 72 – 102 months). Median single dose per fraction was 2.0 Gy (range, 1.5 – 2 Gy) and median total dose was 30.6 Gy (range, 16 – 45 Gy). Radiotherapy was performed in 2D (n = 10; 13.3%), 3D (n = 63; 84.0%) and VMAT (n = 2; 2.7%) techniques, respectively. The median PFS was 14.0 years (95%-CI: 8.3 – 19.7 years). The estimated PFS after 5 and 10 years were 73.0% and 65.5% in Kaplan-Meier analysis, respectively. The 5- and 10- year LC were 94.9% and 92.3%, respectively. The 5- and 10-year OS were 88.6% and 73.9%. In univariate analyses of PFS, younger patients (≤ 60 years old) had significantly superior PFS to those older than 60 years old (5-year PFS 81.9% vs. 65.1%, p= 0.021). Dose escalation >36.0Gy had no prognostic influence in term of PFS (p= 0.543). Extranodal involvement, stage and histology had no prognostic impact on PFS. Depending on the site of lymphomas, the most common acute side effects were: dermatitis CTCAE °I - II (8.0%), xerostomia CTC °I (8.0%), cataract CTC °I (12.0%) and dry eyes CTC °I - II (14.6%). No adverse event CTC° III was reported. Most acute side effects recovered at 3 to 6 months after radiotherapy except for CTC °I cataract and xerostomia. Conclusion Local Radiotherapy was highly effective for treatment of early stage iNHL with no serious side effects in our cohort. The most acute CTCAE °I – II side effects recovered 3 to 6 months later. Technique advances seem to have further improved effectiveness and tolerability of radiotherapy. Trial registration: Local ethics committee of Ludwig-Maximilian-University (LMU) Munich approved this retrospective analysis on the May 7th, 2019 (Nr. 19-137).