ESTRO 2023 - Abstract Book

S932

Digital Posters

ESTRO 2023

G. Facondo 1 , M. Serio 1 , G. Vullo 1 , M.P. Bianchi 2 , S. Pelliccia 2 , A. Di Rocco 3 , T. Lanzolla 4 , M. Valeriani 1 , V. De Sanctis 1 , M.F. Osti 1 1 Università degli Studi di Roma "La Sapienza", A.O.U Sant'Andrea M-P, Radiation Oncology, Rome, Italy; 2 Università degli Studi di Roma "La Sapienza", A.O.U Sant'Andrea M-P, Hematology, Rome, Italy; 3 Università degli Studi di Roma "La Sapienza", Policlinico Umberto I, Hematology, Rome, Italy; 4 Università degli Studi di Roma "La Sapienza", A.O.U Sant'Andrea M-P, Nuclear Medicine, Rome, Italy Purpose or Objective To evaluate the efficacy of residual site radiation therapy (RSRT) in term of progression free (PFS) and overall survival (OS) in patients with primary mediastinal lymphoma (PMBCL) with Deauville Score 4 (DS 4) following rituximab and chemotherapy treatment (R-CHT) in a monoinstitutional retrospective study. Materials and Methods Between 2010 and 2022 we analysed 31 patients with PMBCL with median age of 34 years (range 16-52years). Thirteen patients were females and 18 were males. At the end of R-CHT, patients were evaluated by 18F-fluorodeoxyglucose positron-emission tomography, showing DS4, and were treated with adjuvant RSRT. RT was delivered by Intensity modulated radiation therapy (IMRT) and three-dimensional conformal RT (3D-CRT). The gross tumor volume (GTV) included morphological mediastinal residual disease after R-CHT. Most patients underwent image-guided radiotherapy (IGRT) using cone-beam computed tomography (CBCT) system as daily pre-treatment imaging. All patients were evaluated every 3 months for the first 2 years and every 6 months afterwards for a period of at least 5 years with clinical and radiological procedures as required. The Kaplan-Meier method was used to calculate survival curve estimates. Results All patients received RSRT with a dose of 30 Gy in 15 fractions. Median follow-up was 43 months (range 1-148 months). The median survival was 49 months (range 8-155 months) and 10-years OS was 100%. 1 year and 5 years PFS was 96.6% and 91.5% respectively. Patients with progressive disease have been treated with high-dose chemotherapy (HDC) and/or autologous stem cell transplant (auto-SCT.) U.A. Corro Verde 1 , U.A. Corro Verde 2 , C. De La Fuente Alonso 2 , J. Romero Fernandez 2 , M. López Valcárcel 3 , B. Gil Haro 2 , J. Velasco Jimenez 2 , R. Benlloch Rodriguez 2 , S. Santana Jimenez 2 , L. Paisán Palacio 2 , R. Rubiato Aragon 2 , A. Valcárcel Diaz 2 , P. Sarrión Rubio de la Torre 2 , O. Engel 2 , J.F. Obeso Herrera 2 , I. Zapata Paz 2 , M. Hernández Miguel 2 , S. Cordoba Largo 2 1 Hospital Universitario Marqués de Valdecilla, Serivicio de oncología radioterápica, Santander, Spain; 2 Hospital Universitario Puerta de Hierro, Servicio de oncología radioterápica, Madrid, Spain; 3 Hospital Universitario Puerta de Hierro, Servicio de oncología radioterápica, Madrid, Spain Purpose or Objective Total body irradiation (TBI) has been an important component of the conditioning regimen for allogeneic myeloablative hematopoietic stem cell transplantation (HSCT) in acute lymphoblastic leukemia (ALL). The myeloablative conditioning regimen has two aims: (1) to eradicate leukemic cells, and (2) to prevent rejection of the graft. Its use as conditioning regimen for ALL is progressively declining because concerns of toxic effects in favour of chemotherapy-based regimens. This retrospective study aimed to asses that the schedule of 10Gy (2Gy/fraction) give similar results to that reported for classic fractionation (12-15Gy). Materials and Methods Between 2011-2021, sixty-four patients were treated with TBI conditioning regimen with myeloablative intention. Most patients had a diagnosis of ALL (52/64patients). Fifty-eight patients received 10Gy (90.6%); 12Gy (4.7%), 6Gy (3.1%) and 4Gy (1.6%) in 2Gy per fraction/twice/daily. Patients were positioned in lateral decubitus with lung shielding to limit the average lung dose to 8Gy. In vivo dosimetry was used in all patients. Fifty-six percent achieved complete response with first chemotherapy line before TBI. Forty-four percent needed multiples induction regimens of chemotherapy to achieve response before receiving TBI. The donors were as follow: HLA-matched sibling donor (50.3%), unrelated donor (20%), umbilical cord blood (28.1%) and one case (1.6%) haploidentical transplant. Conclusion RSRT in patients with PMBCL treated with ICHT and DS 4 did not impact unfavourably on patient survival. PO-1166 Total Body Irradiation (TBI) for hematopoietic stem cell transplantation

Results

Mean follow-up: 35 months (range 0-136). Mean overall survival (OS): 42.4 weeks (CI95: 29.2-55.6). One and 2-years overall survival (OS) were 58% and 35%, respectively. Recurrent disease was observed in 17 patients. The median disease-free survival was 7.1months (CI95: 3.4-11.1). Acute side effects are described in Table 1.