Long-Term Results of IFRT vs. ISRT in Infradiaphragmal Fields in Aggressive Non-Hodgkins's Lymphoma Patients-A Single Centre Experience

Simple Summary: Radiotherapy plays a crucial role in managing lymphomas. Advancements in radiation oncology have resulted in smaller treatment volumes and an improved ability to avoid nearby critical tissues and organs. Additionally, radiation therapy doses have been reduced. Our retrospective study aimed to compare the efficacy and side effects of involved-field (IFRT) versus involved-site radiotherapy (ISRT) fields in infradiaphragmal aggressive non-Hodgkin lymphoma. Addressing the persistent concern of radiotherapy toxicity, our findings highlight that scaling down the treatment volume and doses maintains efficacy and local control without compromising patient outcome. Furthermore, this approach significantly reduces both acute and long-term side effects. (1) Background: This study aimed to examine the difference in efficacy and toxicity of involved-field (IFRT) and involved-site radiotherapy (ISRT) fields in infradiaphragmal aggressive non-Hodgkin lymphoma patients. (2) Methods: In total, 140 patients with infradiaphragmal lymphoma treated between 2003 and 2020 were retrospectively evaluated. There were 69 patients (49%) treated with IFRT, and 71 (51%) patients treated with ISRT. The median dose in the IFRT group was 36 Gy, (range 4-50.4 Gy), and in the ISRT group, it was 30 Gy (range 4-48 Gy). (3) Results: The median follow-up in the IFRT group was 133 months (95% CI 109-158), and in the ISRT group, it was 48 months (95% CI 39-57). In the IFRT group, locoregional control was 67%, and in the ISRT group, 73%. The 2- and 5-year overall survival (OS) in the IFRT and ISRT groups were 79% and 69% vs. 80% and 70%, respectively (p = 0.711). The 2- and 5-year event-free survival (EFS) in the IFRT and ISRT groups were 73% and 68% vs. 77% and 70%, respectively (p = 0.575). Acute side effects occurred in 43 (31%) patients, which is more frequent in the IFRT group, 34 (39%) patients, than in the ISRT group, 9 (13%) patients, p > 0.01. Late toxicities occurred more often in the IFRT group of patients, (10/53) 19%, than in the ISRT group of patients, (2/37) 5%, (p = 0.026). (4) Conclusions: By reducing the radiotherapy volume and the doses in the treatment of infradiaphragmatic fields, treatment with significantly fewer acute and long-term side effects is possible. At the same time, efficiency and local disease control are not compromised.