ESTRO 38 Abstract book

S29 ESTRO 38

J. Brady 1 , N.G. Mikhaeel 1,2 1 Guy's and St.Thomas' NHS Foundation Trust, Department of Clinical Oncology, London, United Kingdom; 2 King's College, Division of Cancer Studies, London, United Kingdom Purpose or Objective Persistent metabolic activity on 18-FDG PET-CT at completion of first-line chemotherapy in diffuse large B cell lymphoma (DLBCL) is associated with poor prognosis. Fit patients can be offered salvage high-dose therapy if refractory disease is confirmed, but there is no standard treatment for less fit patients. Radiotherapy is as an effective treatment for DLBCL and commonly used as part of planned combined modality treatment for localised disease. Its value in patients with localised refractory disease remains to be defined. In this study we aim to evaluate to outcome for patients with incomplete metabolic response (Deauville score 4-5) following first-line chemotherapy who underwent RT to sites of persistent activity. Material and Methods We performed a retrospective review of all patients with DLBCL who received RT at our institution having not achieved a complete metabolic response after first-line chemotherapy. This was defined as a Deauville Score (DS) of 4 or 5 on PET-CT. Eligible patients received RT to a radical dose (≥30Gy in 1.8-2Gy fractions). We collected data on patient, disease and treatment characteristics. Outcomes included relapse rate, site of relapse, time to progression and overall survival (OS). Post radiotherapy PET-CT response was also recorded. Results 41 patients who received RT between March 2011 and July 2018 were identified. Patient and disease characteristics are shown in the table below.

Conclusion We have identified the max dose to the right atrium and right coronary artery as the cardiac sub-structures responsible for the greatest dose-related impact on patient survival. A max dose of 22.5Gy was identified and should be considered for these as avoidance structures in future planning studies.

With median 24.3 months of follow up from completion of RT (range 1.7-78.5), 13/41 patients have relapsed/progressed (31.7%). 8 relapses were out of field, 3 both in and out of field and 2 progressed in field only. Median time from completion of RT to progression was 4.0 months (0.8-51). Of patients with relapsed/progressive disease, 6 received salvage high-dose chemotherapy, and 3 are alive and in

Proffered Papers: CL 2: Proffered papers Haematology, Sarcoma and oligometastases

OC-0066 Effectiveness of radiotherapy for patients not in metabolic remission after chemotherapy for DLBCL