ESTRO 2020 Abstract Book

S203 ESTRO 2020

OC-0374 Does low-dose TBI improve outcome in patients with early stage low grade NHL? (EORTC 20971-22997) M. Beijert 1 , P. Soubeyran 2 , S. El Badawy 3 , L. Specht 4 , K. Verschueren 5 , C. Ong 6 , R. Maazen 7 , I. Aurer 8 , B. Ta 9 , A. Neven 10 , B. Meulemans 10 , C. Fortpied 10 , B.M.P. Aleman 11 1 UMC Groningen, Department of Radiation Oncology, Groningen, The Netherlands ; 2 Institut Bergony, Radiation Oncology, Bordeaux, France ; 3 National Cancer Institute, Radiation Oncology, Cairo, Egypt ; 4 Rigs Hospitalet University of Copenhagen, Oncology, Copenhagen, Denmark ; 5 B.Verbeten instituut, Radiation Oncology, Tilburg, The Netherlands ; 6 Medisch Spectrum Twente, Radiation Oncology, Enschede, The Netherlands ; 7 Radboud University Medical Center, Radiation Oncology, Nijmegen, The Netherlands ; 8 KBC Zagreb University of Zagreb, Radiation Oncology, Zagreb, Croatia ; 9 Maastro Clinic, Radiation Oncolgy, Maastricht, The Netherlands ; 10 EORTC Headquarters, EORTC Headquarters, Brussels, Belgium ; 11 Netherlands Cancer Institute, Radiation Oncology, Amsterdam, The Netherlands Purpose or Objective Localized low grade non-Hodgkin lymphoma (NHL) can effectively be treated with radiation but there is a high chance of relapse. Low grade lymphomas are extremely sensitive to radiation even at low doses. Low dose total body irradiation (TBI) might improve outcome by eradicating microscopic disease. Therefore, the EORTC performed a randomized phase III trial evaluating whether the addition of low-dose TBI could improve the outcome in patients with stage I/II indolent NHL, treated with involved field radiotherapy (IFRT). Material and Methods Patients with previously untreated indolent NHL were randomly assigned to IFRT (26-40 Gy/13-20 fractions; IFRT only) or to TBI (1.5 Gy/10 fractions in 2 courses with a 2- week split) followed by IFRT (as in the IFRT only arm), 4 weeks after the TBI (TBI+IFRT). The primary endpoint of the study was progression-free survival (PFS). Secondary endpoints included overall survival (OS) and response to low-dose TBI. The original aim was to include 344 patients in 6 years. Due to poor accrual, the trial was closed prematurely after 9 years. The final analysis was postponed because the prognosis observed in the control arm was better than originally anticipated. Results Between 2000 and 2009, 203 patients were entered into the trial. Baseline clinical characteristics (gender, stage, pathological subtype) were well balanced between both treatment arms. Median age was 54 years (range 21-85). 84% of the patients had follicular lymphoma. Acute toxicity of treatment was mild in both arms. In the TBI+IFRT arm CTCAEv2 grade 3/4 neutropenia, thrombocytopenia and anemia were observed in 3.0, 1.0 and 1.0% of patients, respectively. Among the 129 patients in both arms with a measurable mass at randomization, 105 had a complete remission (unconfirmed) (CR(u)), with no meaningful difference between both arms. TBI in itself induced a CR(u) rate of 34.8% and a partial remission rate of 33.3%. After a median follow up of approximately 13 years progressive disease/relapse or death was observed in 60 patients in the IFRT and in 54 patients in the TBI+IFRT arm. A second primary tumor was the main cause of death in both treatment arms (see table). Second primary tumors were observed in 17 (16.8%) and 16 (15.7%) of patients treated with IFRT and TBI+IFRT, respectively. Only 1 MDS was observed (after TBI+IFRT). The 5-, 10- and 15-year

per arm) are needed. A preliminary analysis was performed when the preplanned number of events (n=20) was reached. Results RESULTS:At the time of our analysis 40 patients were enrolled, 19 (49%) in the TAE/TACE and 21 (51%) in the SBRT arm respectively. Median age was 75 (range 52- 86) years. All patients received at least ≥ 1 TAE/TACE course prior to enrolment; no significant differences were found between the 2 arms with regard to prior resection (n=8, 20%), Radiofrequency Ablation (RFA, n=14, 35%) or Percutaneous Ethanol Injection (PEI, n=4, 10%). Median follow-up was 18 months (range, 2-56 months). Patients were classed stage A and B according Barcelona Clinic Liver Cancer (BCLC) staging system in 7 (18%) and 33 (82%) respectively. One and 2-year LC rates were 57% and 36%, with a median LC of 12 months (CI95% 16-33 months). Use of SBRT resulted in superior LC as compared to TAE/TACE (median not reached versus 8 months, p=0.0002). PFS was 29% and 16% at 1 and at 2 years, respectively. At the event of progression, 8 patients in the SBRT arm received a further TAE/TACE administration while 10 patients in the TAE/TACE arm received SBRT. OS was 96% and 90% at 1 year and at 2 years, respectively. No grade ≥3 toxicity was recorded, and no differences in overall toxicities were found between the 2 arms.

Conclusion In patients affected by unoperable HCC experiencing incomplete response following ≥1 cycle of TAE/TACE, SBRT was correlated to significantly higher LC rates as compared to rechallenge with TAE/TACE.