ESTRO 2023 - Abstract Book

S1276

Digital Posters

ESTRO 2023

1 University Hospital Zurich (USZ); University of Zurich (UZH), Radiation Oncology, Zurich, Switzerland; 2 University of Zurich (UZH), Faculty of Medicine, Zurich, Switzerland; 3 University Hospital Zurich (USZ); University of Zurich (UZH), Nuclear Medicine, Zurich, Switzerland; 4 University Hospital Zurich (USZ); University of Zurich (UZH), Hematology and Oncology, Zurich, Switzerland Purpose or Objective Growing evidence supports a combined modality treatment strategy including definitive local therapy of all macroscopic cancer sites for patients with oligometastatic disease. However, the lack of phase III trials and uncertainties with respect to patient selection and details of multimodality treatment highlight the importance of the multidisciplinary tumor board (MDT) in the decision-making process. This study aimed to assess the patterns-of-use of MDTs for oligometastatic patients, and analyze the recognition and treatment recommendations for oligometastatic patients on an MDT level at a large comprehensive cancer center. Materials and Methods For this retrospective single-center cross-sectional assessment, oligometastatic patients were identified by screening of oncological positron emission therapy (PET) and concurrent brain scans conducted at our center between January and December 2020. MDT discussions and recommendations within four weeks of the imaging diagnosis of oligometastatic disease were quantified and analyzed. Results A total of 787 oligometastatic cases were identified. The most common primary tumors were lung cancer and mesothelioma, skin cancer, and prostate cancer with 231 (29%), 160 (20%), and 84 (11%) cases, respectively. Almost half of the cases (46%) had one metastasis on imaging only. More than half (56%) of all oligometastatic cases were discussed at an MDT within four weeks following imaging-based diagnosis of oligometastatic disease. Radiotherapy and surgery were part of the recommended therapeutic regimen in 16% and 7% of cases, respectively, and a multimodal approach including some form of definitive local therapy was recommended in 15% of cases (see Figure 1 and Figure 2). On logistic regression analysis, only oligometastatic skin cancer was significantly associated with a recommendation for definitive local therapy, whereas the number of oligometastases did not influence the recommendation of definitive local therapy. Conclusion More than half of oligometastatic cases in this cohort were discussed in MDTs and the treatment recommendation included the use of definitive local therapy in a significant number of these cases. Further research is required to better identify patient and disease characteristics of oligometastatic cancer patients, who benefit most from a combined modality treatment strategy.

PO-1573 Oligometastatic prostate cancer: outcomes and toxicity of stereotactic body radiation therapy (SBRT)

E. Gomis Selles 1 , Ó. Muñoz Muñoz 1 , P. Cabrera Roldán 1 , B.D. Delgado León 1 , J.L. López Guerra 1

1 Virgen del Rocio University Hospital, Radiation Oncology, Sevilla, Spain

Purpose or Objective SBRT is a method of external beam radiotherapy (EBRT) that precisely delivers a high irradiation dose to a target in one or few treatment fractions. These characteristics make it a logical choice for metastasis-directed therapy in prostate cancer. The main endpoint of this analysis is to assess the impact of this strategy on disease control. The secondary objective is to evaluate the toxicity of SBRT. Materials and Methods Retrospective cohort study selecting patients with oligometastatic prostate cancer who received SBRT for metastases in a single institution between 2017 and 2022.