Outcomes of Patients Treated With RCHOP With a PET-Adapted Approach for Consolidative Radiotherapy: A Retrospective Single-Center Study at the Royal Marsden Hospital

BACKGROUND: Treatment with CHOP-based chemotherapy with consolidative radiotherapy (CRT) for primary mediastinal B cell lymphoma (PMBCL) has been the standard approach in the pre-rituximab era. Overtreatment with CRT for patients who may have already been cured by primary immunochemotherapy in the rituximab era is a significant concern due to the long-term toxicity associated with radiotherapy. Positron emission tomography (PET) may help to identify patients who may not benefit from further CRT. METHODS: We conducted a retrospective review of patients treated at the Royal Marsden Hospital between 2003 and 2020 for PMBCL to assess CRT use and survival outcomes. RESULTS: Forty-three patients were identified, with 95% of the patients receiving R-CHOP. CRT was given in 5 patients. Five-year event-free survival was 79% (95% confidence interval: 64%-89%) and 5-year overall survival was 88% (95% confidence interval: 73%-95%). Seven of 9 patients with DS4 did not receive CRT and instead monitored with serial PET scans. None of these 7 patients relapsed in the mediastinum. CONCLUSION: CRT may be omitted in patients with a negative end of treatment PET scans; however, careful observation may also obviate the need for CRT in PET positive patients.