ESTRO 2021 Abstract Book

S1023

ESTRO 2021

6 Department of Experimental, Diagnostic and Specialty Medicine - DIMES , Alma Mater Studiorum Bologna University, Bologna, Italy

Purpose or Objective Primary aim was, in patients (pts) undergoing SIRT, to compare 99m Tc-labeled macroaggregated albumin distribution at hepatic artery perfusion scintigraphy and SPECT/CT (MAA scan) with 90Y-resin-microspheres PET/CT distribution. Secondary aim was to correlate scan results with treatment response. Materials and Methods A retrospective single center analysis was performed including pts who underwent MAA scan and 90Y-PET/CT, pre and post-SIRT respectively, between November 2016-October 2018, with available clinical/imaging follow- up (FU). We evaluated: a) absent/partial/complete distribution match between MAA and 90Y-resin- microspheres on target hepatic lesion and, when present, on neoplastic thrombosis; b) response to treatment (performing ceCT or MRI at least every three months after SIRT). Results Overall 49 pts with primary HCC were included (11F-38M; mean age: 65 ± 11years; range:39-88years). At least one previous treatment (surgery, chemotherapy, TACE/TAE or radiofrequency) was received by 20/49 pts. 1/49 PET post-SIRT was not available for technical issues. In 47/48 pts there was a good distribution match between MAA and 90Y-microspheres, with complete target lesion correspondence (in 3/48 pts target was only partially covered). Among the 27/48 pts with neoplastic thrombosis, 26/27 presented a complete MAA-90Ymicrospheres correspondence (in 2/27 pts thrombosis was only partially covered). Mean dose delivered to the tumor calculated with partition model-MIRD was 260Gy (range:53,8-679,8Gy) and mean dose to the whole liver was 9,3Gy (range:1,5-24,7Gy). Extra-hepatic activity in 90Y-PET was detected in 4/48 pts (1lung;1 gallbladder and bowel;1 gallbladder;1 gastro-duodenal spots). No significant complications were observed after SIRT procedure, except one case of pneumonia. Mean FU was 17.6months (range:1-39months). 5/49 pts were lost at FU. At last FU we recorded: complete response (CR) in 9/44 pts (20,5%), partial response (PR) in 1/44 (2,3%), stable disease (SD) in 17/44 (38,6%) and progressive disease (PD) in 17/44(38,6%). Overall, 3 cases presented with target CR+thrombosis SD whereas a single case target CR+thrombosis PD. Conclusion Our results confirm that a careful MAA scan evaluation reliably reflects 90Y-resin-microspheres distribution and impacts on SIRT response. Further analyses are ongoing in order to establish a possible prognostic value in terms of progression free survival and to search for potential imaging predictive factors of treatment response. PO-1240 Complete pathological response after high dose radiotherapy for locally advanced esophageal cancer. O. Hernando-Requejo 1 , M. Lopez 2 , X. Chen 2 , R. Alonso 2 , E. Sanchez 2 , A. Montero 2 , R. Ciervide 2 , B. Alvarez 2 , J. Valero 2 , M. Garcia 2 , D. Zucca 3 , J. Garcia 3 , P. Garcia de Azilu 3 , L. Alonso 3 , M.A. De la Casa 3 , A. Prado 3 , J. Marti 3 , P. Fernandez Leton 3 , M. Nuñez 2 , M. Izquierdo 2 , K. Rossi 2 , C. Cañadillas 2 , C. Rubio 2 1 HM Hospitales, Radiation Oncoloy, Madrid, Spain; 2 HM Hospitales, Radiation Oncology, Madrid, Spain; 3 HM Hospitales, Medical Physics, Madrid, Spain Purpose or Objective Neoadjuvant radio-chemotherapy is the standard treatment of locally advanced esophageal cancer, as it increases local control and survival. Usually, 10-20% of pathological complete responses are reported in the literature. We describe our experience with increase-dose modulated radiotherapy, in an attempt to probe an increase in pathological complete response in operable patients and an increase of local control (LC) for those From July 2016 to January 2021, 38 patients were treated with neoadjuvant or radical intention. IMRT or VMAT techniques were performed in all cases. Irradiation volumes included: GTV (macroscopic tumor and regional affected nodes, in 76% patients based on PET-CT uptake), CTV (GTV+2cm craniocaudal for microscopic risk of disease) and PTV (CTV+0.5cm). PTV median dose was 50.3Gy (46-50.6Gy) with a median Integrated-Boost dose to GTV of 57.4Gy (54-62.5Gy), in 23 to 28 fractions (in 25 patients (66%), the dose per fraction was 2.2Gy to PTV and 2.5Gy to GTV, in 23 fractions). Sixteen patients (42%) received neoadjuvant chemotherapy, followed by chemo-radiation. The median time from neoadjuvant radiotherapy to surgery was 13 weeks. Results The median age was 63 years old, 92% (35) were males. The more frequent histology was adenocarcinomas (68%) followed by squamous-cell carcinomas (29%). Localization of the tumor was upper (15.8%), middle (5.3%), and lower (78.9%). The clinical Stage was St I (5.3%), St IIa (7.9%), St III (39.5%), St IVa (21.1%), and St IVb (2.6%). In 29 patients (76%) with initial diagnostic PET-CT, maximum SUV in post neoadjuvant PET-CT was significantly lower (p=0.04). Surgery was performed in 55.6% of the patients and a pathological complete response was achieved in 55.6 % of the specimens. With a median follow-up of 10 months, actuarial LC at 2 years was 85.1%, median LC was not reached. The presence of metastatic progression after treatment significantly increases the risk of loco-regional failure (p=0.005), There was a trend towards an increase in LC for patients undergoing surgery (p=0.09). Median disease-free survival (DFS) was 31 months, the only factor related to a trend towards an increase in DFS was concurrent radio-chemotherapy (p=0.07). Mean overall survival (OS) was 22 months, only patients treated in a neoadjuvant approach were related to longer survivals when compared with those in a radical attempt (p=0.02) (Figure 1). Grade I-II acute toxicity was present in 47.2% and 36.1% respectively and Grade III in 7.9%. Only Grade I and II chronic adverse effects were observed in 11.1% and 3.7% of the patients. with radical approaches. Materials and Methods