ESTRO 37 Abstract book

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ESTRO 37

end of treatment for acute toxicity and at 3, 6 and 12 months for late toxicity and treatment response with 18 F- FDG PET-CT. Results Primary site was colorectal in the majority of lesions (16 out of 41), mean metastasis diameter was 20 mm (range 10-60). At a median follow up of 12 months (range 2-30), 15 of 22 (68%) patients are alive. BED >70Gy was prescribed in 83% of cases. At 3 months (m) complete response (CR), partial response (PR), stability of disease (SD) and progression of disease (PD) was observed in 66%, 27%, 3% and 4%, respectively. At 6m 46% of patients had a CR, 3% a PR and 22% a PD. At 12m there were 27% CR and 7% PD. 65% of liver recurrences were out of field. No cases of ≥ G3 acute and late toxicity were reported. Conclusion Risk-adapted dose prescription and image-guided SBRT is an effective and safe option for LM. The role of PET-CT parameters as predictors of response after SBRT for these patients is a very interesting aspect to investigate in the future; however, further clinical evaluation is warranted. EP-1415 SBRT for unresectable locally advanced pancreatic cancer: risk-adapted dose prescription F. Gregucci 1 , S. Fersino 1 , R. Mazzola 1 , D. Aiello 1 , U. Tebano 1 , S. Corradini 2 , M. Cirillo 3 , R. Ruggieri 1 , F. Alongi 4 1 Sacro Cuore Don Calabria Cancer Care Center, Radiation Oncology, Negrar, Italy 2 LMU Munich, Radiation Oncology, Munich, Germany 3 Sacro Cuore Don Calabria Cancer Care Center, Medical Oncology, Negrar, Italy 4 University of Brescia- Sacro Cuore Don Calabria Cancer Care Center, Radiation Oncology, Negrar, Italy Purpose or Objective As stated by the ASCO 2016 guidelines, Stereotactic Body Radiation Therapy (SBRT) represents a new treatment option for locally advanced pancreatic cancer (LAPC). An accurate treatment planning with risk-adapted dose prescription with adherence to specific dose constraints for organs at risk (OARs), and the use of daily Cone Beam CT (CBCT) for image-guidance, could allow an effective and safe treatment delivery. Here, feasibility and efficacy of SBRT in LAPC treated in our Cancer Care Between August 2014 and December 2016, 33 unresectable LAPC patients underwent SBRT. In order to respect OAR dose-constraints a risk-adapted dose prescription strategy was adopted, choosing between the following schedules: 42 Gy or 45 Gy in 6 daily fractions with a biologically effective dose (BED) >70 Gy 10 and 36 Gy in 6 fractions (estimating a BED 57.6 Gy 10 ). SBRT was delivered with volumetric modulated arc technique (VMAT) using RapidArc and flattening filter-free (FFF) mode. Image guidance was performed by means of CBCT before every treatment session. The patients were evaluated at the end of treatment for acute toxicity and at 3, 6 and 12 months for late toxicity and treatment response. Results At the time of analysis, the median follow up was 18 months (range, 5-34 months). Prior to SBRT, 24 out of 33 patients received induction chemotherapy. Although all patients were previously judged as unresectable, 6 out of 33 (18%) underwent surgery after SBRT; all of them received a BED >70 Gy 10 . One-year LC and OS were 81% and 75%, respectively. A total of 12 patients (37%) had an extra-pancreatic progression. No cases of ≥G3 acute and late toxicity were reported. Conclusion In our experience, the risk-adapted dose prescription and image-guided SBRT represent an effective treatment option for LAPC patients. The present results, showed good tolerability without severe toxicity. Probably, in Center are reported. Material and Methods

case of dose reductions below BED <70 Gy due to OAR dose limits, an early combination with systemic therapies could optimize the oncological outcome. EP-1416 Postoperative proton therapy for pancreas cancer patients on the Proton Collaborative Group registry R. Nichols 1 , C. Morris 1 , K. Prabhu 2 , W. Hartsell 3 , O. Cahlon 4 , S. Apisarnthanarax 5 , L. McGee 6 , C. Vargas 6 1 University of Florida Proton Therapy Institute, Radiation Oncology, Jacksonville- Florida, USA 2 Procure Proton Therapy Center- Oklahoma City, Radiation Oncology, Oklahoma City, USA 3 Northwestern Medicine Chicago Proton Center, Radiation Oncology, Chicago, USA 4 Memorial Sloan Kettering Cancer Center, Radiation Oncology, New York, USA 5 Seattle Cancer Care Alliance Proton Therapy Center-, Radiation Oncology, Seattle, USA 6 Mayo Clinic - Phoenix- Arizona, Radiation Oncology, Phoenix, USA Purpose or Objective The PCG registry is a multicenter registry for patients receiving proton therapy for various malignancies. The current abstract reviews the outcomes for patients receiving postoperative proton therapy for resected pancreatic cancer. Material and Methods From 3/2013 to 8/2016 18 patients with resected pancreatic adenocarcinoma received postoperative proton therapy. The current study reviews the pretreatment characteristics and outcomes for these patients. Results Median age -70 years (range 52 to 79); Males 12, Females 6; pT Stage -T2–4, T3–13, T4–1; N Stage -N1–12, N0–6; Margin Status -Close-8, Positive-4, Negative-6; Surgical approach -open-16, laparoscopic 2; Operations performed: standard pancreaticoduodenectomy-11, pylorus sparing pancreaticoduodenectomy-4, total pancreatectomy-1; Pancreaticoduodenectomy with portal vein reconstruction –1; Pancreaticoduodenectomy with irreversible electroporation. Median lymph nodes taken- 16.50 (range 3 to 72); Median lymph nodes positive-1.5 (range 0 to 7); PNI positive-9, PNI negative-2, PNI unknown-4; LVI positive-7, LVI negative-6, LVI unknown- 5; Median tumor size –3.1cm (range 2.2 to 6.2); Median dose delivered –50.51Gy(RBE) (range 27.88 to 54.00); Median treatment duration –38 calendar days (range 25 to 48); One patient died during treatment. One additional patient demonstrated grade 3 toxicity (anorexia, nausea, diarrhea). Only one patient’s treatment was protracted by more than 5 days. Median available follow up is 1.1 years (range 0.07 to 3.4 years); 2 year survival 37%.

Conclusion Postoperative proton therapy after pancreatectomy was well tolerated without treatment interruption or severe toxicity.