Treatment outcomes using involved field and involved site radiotherapy for NHL and HL: Retrospective analysis from a large UK Radiotherapy centre

Abstract

Introduction: Radiation remains the most active modality in the treatment for most types of lymphomas such as combined modality of treatment (CMT) for limited stage high grade (HG NHL) and classical Hodgkin's lymphoma (HL) and radiation alone for low grade limited stage lymphomas (LG NHL). Radiation is also used as consolidation at the end of chemotherapy for advanced stage HG NHL and HL at the site of bulky disease. Radiotherapy has evolved over last few decades. A large phase III randomised clinical trial with more than 1000 patients with a median follow up of 5.6 years has shown no loss of efficacy for dose of 24 Gy in 12 fractions for LG NHL and 30 Gy in 15 fractions for HG NHL as compared to 40 to 45 Gy. Involved site radiotherapy (ISRT) is now standard of care based on recommendations published in 2013. Clinical target volume (CTV) in ISRT is based on macroscopic disease present at the time of diagnosis. We present here the retrospective analysis of the radiotherapy outcomes with IFRT prior to recommendations and ISRT after the recommendations. Methods: This retrospective study included 145 lymphoma patients from 2010 to 2015 with median follow up of 30.5 months (1-83). Patients were identified from the radiotherapy database, and further data were collected from electronic patient records. Statistical analysis was carried out on IBM SPSS Statistics version 24 for windows. Time for treatment failure (TTF) was calculated from date of radiotherapy to progression. Overall survival (OS) was calculated from the date of radiotherapy to last follow-up or death. Clinical notes were reviewed to identify the site of failure with respect to within radiation field or close to the radiation field or distant failure. Results: 0.007 In favour of ISRT TTF related to IFRT/ISRT (log rank test; P value) 0.011 In favour of ISRT Conclusion: Our large retrospective real life data confirm ISRT is non-inferior to IFRT. The differences seen in FL cohort may be due to better staging in recent years with increased use of staging PET scans. Keywords: follicular lymphoma (FL); Hodgkin lymphoma (HL); non-Hodgkin lymphoma (NHL)