ESTRO 2023 - Abstract Book

S1114

Digital Posters

ESTRO 2023

Conclusion Our analysis study was unable to demonstrate any statistically significant difference in OS in patients treated with dCRT or nCRT. Shared-decision making and tailoring treatment to the various patient- and treatment-related factors are crucial when defining the optimal treatment plan.

PO-1384 Stereotactic Radiotherapy for Patients with Small Pancreatic Neuroendocrine Tumors

M. Lopez Gonzalez 1 , E. Sanchez 2 , O. Hernando 2 , R. Ciervide 2 , A. Montero 2 , X. Chen 2 , B. Alvarez 2 , E. De Vicente 3 , Y. Quijano 4 , C. Rubio 2 1 HM Sanchinarro , Radiation Oncology , Madrid, Spain; 2 HM Sanchinarro, Radiation Oncology, Madrid, Spain; 3 HM Sanchinarro, Surgery, Madrid, Spain; 4 Hm Sanchinarro, Surgery, Madrid, Spain Purpose or Objective Surgery is standard treatment for pancreatic-neuroendocrine-tumors (TNP) although it is occasionally associated with high rates of morbid-mortality. Radiotherapy can be an effective alternative in selected patients.

Our objective is to evaluate the efficacy of SBRT (Stereotactic-body-radiation-therapy) as a radical treatment for TNP.

Materials and Methods Between December 2017 and November 2022, we prospectively analyzed 16 patients with a pathological diagnosis of TNP of <2cm treated with SBRT as a part of an IRB-approved study.

The endpoints of the study are local-control, tolerance, progression-free-survival and overall-survival.

Patients’ characteristics: 7 female (43,75%) and 9 male (56,25%) with a mean age of 55.5 years-old. Tumor location: head 3p (23%), neck 4p (23%), body 7p (46%) and tail of pancreas 2p (8%). An octreoscan prior to radiotherapy was positive in 11p (68,7%). FDG-PET was negative for all but one patient (SUV <4). Before SBRT, two internal fiducial markers were placed into the tumor by endoscopic ultrasound puncture and a simulation CT was obtained. Clinical-target-volume (CTV) included pancreatic tumor. Planning-target-volume (PTV) was CTV with 5mm expansion. Patients received 40Gy in 5 fractions on an every other day, with IMRT and gating technique. Results With a median follow-up of 22 months (range 4- 47,9), all patients are without evidence of relapse. Acute tolerance was excellent. Only 4p (25%) showed asthenia. One p developed peptic ulcer on follow-up. Conclusion SBRT is feasible and well tolerated and could be an attractive alternative in selected patients with diagnoses of TNP. Further studies are necessary to confirm these results. H. Eijkelenkamp 1 , G. Grimbergen 1 , L. Daamen 1 , H. Heerkens 2 , S. van de Ven 1 , S. Mook 1 , G. Meijer 1 , I.Q. Molenaar 3 , H. van Santvoort 3 , E. Paulson 4 , B. Erickson 4 , H. Verkooijen 5 , W.A. Hall 4 , M. Intven 1 1 University Medical Center Utrecht, Department of Radiotherapy, Utrecht, The Netherlands; 2 Radboud University Medical Center, Department of Radiotherapy, Nijmegen, The Netherlands; 3 Regional Academic Cancer Center Utrecht, Department of Surgery, Utrecht, The Netherlands; 4 Froedtert and Medical College of Wisconsin, Department of Radiation Oncology, Milwaukee, USA; 5 University Medical Center Utrecht, Division of Imaging, Utrecht, The Netherlands PO-1385 Clinical outcomes after MR-guided radiotherapy for pancreatic tumors on a 1.5 T MR-linac

Purpose or Objective