ESTRO 2020 Abstract book

S276 ESTRO 2020

significant VOD, but there was one occurrence among TBI patients. For patients undergoing PBSCT, median time to engraftment as measured with thrombocytes over 50 [K /µL] was 16 and 19 days, and over 20 [K/µL] it was 14 and 16 days for TMI and TBI respectively, which was significant shorter for the TMI group in both cases, (p<0.01). Similar, median days to neutrophil count over 0.5 [K/µL] and 1.0 [K/µL] was 17 versus 18 days and 19 versus 19 days for TMI and TBI respectively. The median difference in estimated glomerular filtration (eGFR) rate 12 months post treatment was -6.9 and -9.6 [mL/min/1.73 m 2 ], a significant less toxicity was seen for the TMI patients, (p<0.05). Acute GVHD was scored using the MAGIC scale, with 1 patient from the TMI group receiving PBSCT score >2, 6 patients from the TBI group was scored >2. Similar amongst patients receiving PBSCT, 1 TMI patient exhibited a moderate to severe chronic GVHD, 5 TBI-patients received a moderate to severe chronic GVHD. The amount of transplanted CD34 stem cells was similar in both cohorts, with a median in both groups of 6.0 [10 6 /kg]. Leukaemia-free survival at 18 months was similar in both cohorts. Conclusion TMI with helical tomotherapy yield similar efficacy on leukaemia survival as TBI, but with a significant difference on toxicity to the kidneys, as measured by eGFR. In addition, most patient from the TMI group receive a fast and robust engraftment with a low occurrence of severe GVHD. OC-0462 Solitary plasmacytoma treated by Lenalidomide-Dexamethasone in combination with radiation therapy M. Fabien 1 , A. Schernberg 2 , A. Arsene Henry 1 , M. Vignon 3 , D. Bouscary 3 , Y. Kirova 1 1 Institut Curie, Paris, Paris, France ; 2 Hopital Tenon, Paris, Paris, France ; 3 Hopital Cochin, Paris, Paris, France Purpose or Objective To evaluate the results of the concurrent use of lenalidomide-dexamethasone with intensity-modulated radiation therapy (IMRT) for solitary plasmacytoma in terms of toxicity and outcome. Material and Methods Forty-six patients were treated for histologically proven SP between June 2007 and June 2018 in our Department. All patients received IMRT. The median total dose was 40 Gy (range, 40-46). Prescription of concurrent Lenalidomide- Dexamethasone with radiotherapy was left discretion of the referring hematologist-oncologist and started the first day of radiotherapy for four cycles. Results Twenty-seven solitary plasmacytoma were treated with IMRT alone and 19 with Lenalidomide-Dexamethasone in association with IMRT. At 5 years, the local control, multiple myeloma-free survival (MMFS) and progression- free survival (PFS) rates were 96.3%, 85.4%, and 60%. MMFS and PFS were significantly higher in the IMRT plus Lenalidomide-Dexamethasone group compared to IMRT alone group (100% vs 77.1%, p=0.02 and 81.7% vs 48.4%,

Conclusion It is reasonable to conclude that most relapses occur within the initially involved sites, and that radiotherapy improves local control. However, the number of relapses is small, and it is difficult to draw conclusions regarding the relapse pattern. Relapses-localization in pediatric patients with HL from all of Denmark will be analyzed. OC-0461 Acute toxicity and recovery following total marrow irradiation compared to total body irradiation J. Engellau 1 , A. Haraldsson 2 , P.E. Engström 2 , S. Warsi 1 , C. Sofie 3 , C. Crister 3 , S. Bäck 2 , S. Engelholm 1 , S. Wichert 1 1 Skåne University Hospital, Department Hematology- Oncology and Radiation Physics, Lund, Sweden ; 2 Skåne University Hospital, Radiation physics- Department Hematology- Oncology and Radiation Physics, Lund, Sweden ; 3 Medical Radiation Physics- Department of Clinical Sciences, Lund University, Lund, Sweden Purpose or Objective The purpose of this study was to retrospectively evaluate the acute toxicity and haematological recovery after allogenic stem-cell transplantation and organ sparing total marrow irradiation (TMI). We compare with historical data where patients were treated using total body irradiation A total of 30 patients receiving TMI between 2014-2019 and 33 patients that received TBI between 2009- 2014 prior to stem cell transplantation (SCT) were evaluated. The TBI and TMI cohort were similar with respect to leukaemia subtypes. The patient group included 5 respective 4 children for the TMI and TBI group that received bone marrow transplantation (BMT) as opposed to peripheral blood stem cell transplantation (PBSCT). Follow up included S-creatine, pulmonary function tests, time to engraftment and scoring of graft versus host disease (GVHD), both acute and chronic. Prescribed dose was 12 Gy in 6 fractions twice daily, TMI was delivered with helical tomotherapy with organ sparing to lungs, kidneys, liver, and bowel. TBI was delivered using lead lung shielding with the patient in a side position at 4.5 meters source to skin distance. Doses to organs at risk for TBI was estimated from central doses and anterior posterior measurements. Results Median age was 31 and 30 years for the TMI and TBI group with a median follow up of 1.7 and 7.9 respectively. The largest difference in dose and NTCP was seen for the kidneys, table 1. One TMI patient received a pneumonitis and one TBI patient, none of the TMI patients received a (TBI) and lung shielding. Material and Methods