Radiotherapy dose de-escalation in patients with high grade non-Hodgkin lymphoma in a real-world clinical practice

Purpose The standard treatment of non-Hodgkin lymphoma (NHL) comprises combined modality treatment, radiotherapy (RT), and chemotherapy with rituximab which has significantly improved both disease-free survival (DFS) and overall survival (OS). However, there is no uniformity in radiation dose usage in these patients. In this retrospective study, we compared lower radiation dose with higher in patients with aggressive NHL. Materials and Methods From 2007 to 2017, treatment records of all high-grade NHL or diffuse large B-cell lymphoma and non-central nervous system NHL were included. We compared response rates, OS and DFS of patients who received ≤30 Gy RT to those with >30 Gy. Univariate and multivariate analyses were done to determine factors affecting prognosis, i.e., age, sex, stage, International Prognostic Index (IPI), adding rituximab, and radiation dose. Results A total of 184 NHL patients treated with combined modality or radiation alone having complete follow-up details were analyzed. At median follow-up of 66.8 months, 5-year OS was 72.8% in high-dose group versus 69.9% in low-dose group (p = 0.772) and 5-year DFS 64.7% versus 64.1% (p = 0.871). Patients having early-stage disease receiving low dose and those with advanced disease treated with >30 Gy had better OS and DFS though not statistically significant. Adding rituximab was associated with significantly better OS and DFS irrespective of radiation dose delivered. High IPI score and omitting rituximab were the only factors that significantly worsened both OS and DFS. Acute radiation toxicities were comparable in both groups (p = 0.82). Among late toxicities, no patient developed a second malignancy and 5% died due to cardiovascular complications (p = 0.595) though only two patients (1.1%) had received thoracic radiation. Conclusion The two groups had comparable response rates, acute toxicities, DFS and OS. This study suggests that RT dose reduction may be possible in high-grade NHL without compromising the DFS and OS. Keywords: Non-Hodgkin lymphoma, Radiotherapy, Late effects, Radiation dose de-escalation