ESTRO 2023 - Abstract Book

S798

Monday 15 May 2023

ESTRO 2023

Materials and Methods This study was a prospective multicenter phase 1 trial which aimed to determine the maximum tolerated dose (MTD) of TMI administered in association with melphalan 140 mg/m ² , followed by autologous stem cell transplantation (ASCT) as consolidation at first relapse in MM. Four dose levels were explored: 8 Gy, 10 Gy, 12 Gy, and 14 Gy. The dose-limiting toxicity (DLT) was defined as: grade 4 neutropenia > 15 days, grade 4 thrombopenia > 28 days, and all other grade 4 non hematologic toxicities except nausea, vomiting, alopecia, mucositis, and reaction to autologous stem cell infusion. Results Thirteen patients were included: only one DLT at the third escalated dose level (12 Gy) was observed, whereas one patient was treated at 14 Gy with no adverse event. The MTD was not reached. The rate of acute toxicity was low: 38% of grade 3/4 diarrhea, mucositis, or unexplained fever. Regarding the lungs, the mean dose administered was systematically less than 8 Gy. After a median follow-up of 55 months, 70% of participants were alive. Of the 13 patients, 38.5% were in very good partial response (VGPR) and 30.8% in complete response (CR). Three of them were progression-free. Six patients were long survivors, still alive after 55 months of follow-up. Conclusion TMI provides good results with a good tolerance profile at first relapse in MM. TMI makes it possible to increase the dose delivered to the PTV while sparing organs at risk (OAR). This technique could be discussed for all regimens before auto- or allo-stem cell rescue when TBI is required. MO-0950 Selected soluble biomarkers in mycosis fungoides and Sézary syndrome: Final results of S-MISR trial K. Elsayad 1 , K. Bormann 2 , T. Nawar 1 , D. Rolf 1 , E.C. Müller 1 , N.B. Pepper 1 , C. Weishaupt 3 , H. Hillmann 1 , E. Bormann 1 , K. Steinbrink 3 , B. Greve 2 , H.T. Eich 1 1 University Hospital Muenster, Radiation oncology department, Münster, Germany; 2 University Hospital Muenster, Experimental radiobiology, Radiation oncology department, Münster, Germany; 3 University Hospital Muenster, Dermatology Department, Münster, Germany Purpose or Objective Soluble biomarker testing has a prognostic potential in several hematological malignancies. Here, we examined the level of selected biomarkers in mycosis fungoides (MF), Sézary syndrome (SS) patients and their correlation with treatment outcomes in the S-MISR prospective study ( S oluble - biomarkers for M ycosis fungo i des and S ézary syndrome patients during and after R adiotherapy). Materials and Methods MF/SS patients received total skin electron beam therapy between 2019 and 2022 at our institute were prospectively recruited (The local ethics committee approved the study protocol). Soluble programmed death-ligand 1 (sPD-L1), soluble CD30 (sCD30), soluble thymus and activation-related chemokine (sTARC), and soluble cytotoxic T lymphocyte-associated antigen-4 (sCTLA-4) were determined before and after treatment with radiotherapy. Disease burden was evaluated with the median modified severity weighted assessment tool (mSWAT). ROC curve analysis was used evaluate the predicting accuracy of different biomarkers and the Youden's index was used determine the optimal biomarkers’ cut-off point. The data has been analyzed according to REMARK guidelines. Results 252 serum samples of sixty-three patients with MF/SS were collected and evaluated by immunoassay. Sixty-three (100%), 48 (76%), and 41 (65%) patients had baseline, post-radiation, and last follow-up samples, respectively. The median follow up for this analysis was 12 months. The median age was 63 years (range: 38-87). The patient population consisted of 52 (83%) MF and 11 (17%) SS patients. The baseline concentrations of sPD-L1, sCD30, and sTARC biomarkers are significantly higher in MF/SS patients than in healthy individuals. Low baseline sPD-L1 and sCD30 levels were associated with higher response rates (P<0.05). At the end of treatment. The level of sPD-L1, sCD30, and sTARC concentrations was associated with the clinical outcome ( Figure 1 ). In a Cox proportional hazard model, CLIC-risk group, ECOG score, baseline WBC count, CRP level, posttherapy level of sPD-L1, sCD30, sTARC, sCTLA-4, sIL-2R: soluble interleukin 2 receptor, interleukin 6, and clinical response to radiotherapy were included. In the multivariate analysis, the posttherapy sPD-L1 and sCD30 levels were associated with progression-free survival (PFS). At the same time point, the sTARC level and ECOG score proved to be significant determinants of overall survival (OS).