ESTRO 2023 - Abstract Book

S1102

Digital Posters

ESTRO 2023

The questionnaire was sent-back to all 22 Italian Institutions performing pancreatic SBRT and previously joined the survey. It asked for general information on the Radiation Oncology Centre; dose prescriptions; treatment planning; SBRT procedures. Results Three centers (14% vs 10% in 2018) treat more than 20 pancreatic cases/year and 32% (vs 18%) between 10 and 20 cases/year. SBRT is performed for unresectable locally advanced pancreatic cancer (LAPC) in 100% and/or for neoadjuvant treatment in borderline resectable (BR) disease in 50% of the centers (Figure 1). In 2018, although 60% of the centers delivered a 5-fraction schedule with a total dose of 25-30Gy, for both LAPC and BR disease, a large variety of fractionation schemes was reported. Currently, the 5-fraction is confirmed as the most used schedule, with an increased total dose range up to 30-40 Gy in the 73% of the centers for LAPC and in the 77% for BR patients. In the 81.8% of the centers the optimal prescription isodose level was between 85-95%, with a heterogeneity dose between 110-120%. Dimensional criteria (>5cm) and tight margins to adjacent structures were the major limiting factors for dose prescription in 63.64% and 100% of the center, respectively. A frameless set-up and organ motion control methods are performed in most of the centers: 71.4% and 81.8% of the centers, respectively. 4 centers performed MRI or PET-CT simulation. For Gross Tumor Volume (GTV) contouring, a dynamic co-registration is preferred (68.2%) with a multiple approach in imaging choice (MDC TC: 64%, MRI: 68%, PET-CT: 64%). In all centers SBRT is delivered during a chemotherapy interval. Concomitant chemotherapy is administered only in clinical trial in one center. When SBRT is administered after chemotherapy, a pause of 2-3 weeks or of 1 week is respected by the 35% and 20% of the centers, respectively.

Conclusion SBRT has found a wide indication for LAPC and BR disease. Our analysis shows that highly effective doses are currently administered according to the available guidelines. Since a certain dose variability remains, a prospective multicenter study could be promoted to evaluate the most effective schedule and the best integration with the systemic therapies currently in use.

PO-1373 Stereotactic Body Radiotherapy in isolated recurrence of pancreatic cancer after radical surgery

M. Massaro 1 , T. Comito 1 , M.A. Teriaca 1 , C. Franzese 1,2 , L. Di Cristina 1,2 , A.M. Marzo 1,2 , G. Reggiori 1 , P. Gallo 1 , M. Scorsetti 1,2

1 IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery, Via Manzoni 56, Rozzano, Milan, Italy; 2 Humanitas University, Biomedical Sciences, Via Rita Levi Montalcini 4, Pieve Emanuele, Milan, Italy Purpose or Objective The aim of the study was to assess the efficacy and the tolerance of stereotactic body radiation therapy (SBRT) in patients affected by isolated recurrence of pancreatic cancer after radical surgery, evaluating clinical outcomes and toxicity profile. Materials and Methods We performed a retrospective analysis on patients with isolated recurrence from resected pancreatic cancer. Prescription dose was 45 Gy in 6 fractions. Primary endpoint was local control (LC), secondary endpoints were distant progression free survival (DPFS), overall survival (OS) and toxicity. Local control was defined according to RECIST criteria. We performed an univariate and a multivariate analysis to evaluate a correlation between endpoints and prognostic factors. Acute and late toxicity was recorded according to NCI Common Terminology Criteria for Adverse Events (CTCAE) v5.0.

Results