Abstract Book

S771

ESTRO 37

Purpose or Objective To investigate metabolic parameters as predictive of local response after Stereotactic Body Radiation Therapy (SBRT) for liver-oligometastases Material and Methods Inclusion criteria of the present retrospective study were: a) metachronous liver oligometastases; b) absence of progressive disease≥6months (mo); c) metastases≤3; d) BED > 100Gy; e) evaluation of SBRT-response by means of 18-FDG-PET/CT for at least two subsequent evaluations; f) Karnofsky performance status >80; g) life-expectancy>6 mo. The following metabolic parameters were defined semi-quantitatively for each metastases: 1) SUV-max; 2) SUV-mean; 3) Metabolic Tumor Volume (MTV)-total tumor volume with a SUV ≥ 2.5; 4) Total Lesional Glycolysis (TLG)-SUV mean × MTV. Local control was defined as absence of recurrence in the field of irradiation. Results Between October 2014 and February 2017, twenty-two patients for a total of forty-one liver metastatic lesions met the inclusion criteria of the study. At the time of the analysis, the median follow up was 16.3 mo (range, 6-32 mo). The most frequent primary tumor sites were colorectal (31%) and lung (24%). Pre-SBRT, median SUV- max was 8.74 (range, 4.49 – 23.59), median SUV-mean was 4.6 (range, 3 – 7.46), median MTV was 5.74 cc (range, 0.9-80.64) and median TLG was 24.1 (range, 3.6 - 601.5). High values of SUV-mean and SUV-max pre-SBRT related to local failure. In detail, at the time of the analysis, the rate of in-field failure was 66.7% in case of pre-SBRT SUV-mean>5 and 61.1% for pre-SBRT SUV- max>10. At statistical analysis, metastases with SUV- mean>5 (p 0.04; OR 4.75, Sensitivity = 50%, Specificity = 82.6%, AUC 0.66) and SUV-max>10 (p 0.02; OR 5.03, Sensitivity = 69%, Specificity = 70%, AUC = 0.69) showed higher rates of in field-failure compared to the remaining lesions. Conclusion According to current findings, pre-SBRT SUV max and SUV mean could predict response in liver oligometastases. To date, biological equivalent dose represents a predictive parameter of local control for liver metastases submitted to SBRT. The present results could be integrated in SBRT strategy in order to customize dose prescription taking into account the single-metastases metabolic profile. EP-1418 SBRT for unresectable locally advanced pancreatic cancer: clinical outcomes on 100 patients T. Comito 1 , C. Franzese 1 , E. Clerici 1 , L. Di Brina 1 , A. Tozzi 1 , C. Iftode 1 , D. Franceschini 1 , G. Carta 1 , S. Tomatis 1 , M. Scorsetti 1 1 Istituto Clinico Humanitas, Radiotherapy and Radiosurgey, Rozzano Milan, Italy Purpose or Objective Pancreatic adenocarcinoma is characterized by a poor prognosis. Surgery is the gold standard of care, however more than 50% of patients are unresectable at the time of diagnosis. In patients with locally advanced pancreatic cancer (LAPC), the integration of chemotherapy (CT) and chemo-radiation treatment (CRT) is the current therapeutic option, associated with a significant toxicity rate and with a disappointing overall survival (OS). In the last years, the role of stereotactic body radiotherapy (SBRT) in the treatment of LAPC was investigated. Higher local control related to the high doses employed, short overall treatment time and sequential integration with systemic therapy, represent the crucial advantages of SBRT over conventional CRT. Objective of this prospective study is to assess the efficacy of SBRT in patients with inoperable LAPC. Material and Methods Patients with unresectable LAPC with maximum tumor diameter ≤ 5cm, without limph node disease and without distant metastasis were treated with SBRT, after

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. EP-1417 SBRT for liver oligometastases:predictive factors of local responce response by 18F-FDG-PET/CT S. Fersino 1 , R. Mazzola 1 , D. Aiello 1,2 , F. Gregucci 1 , N. Giaj-Levra 1 , A. Fiorentino 1 , F. Ricchetti 1 , R. Ruggieri 1 , F. Alongi 1,3 1 Sacro Cuore Don Calabria Cancer Care Center, Radiation Oncology, Negrar, Italy 2 University of Palermo, Radiation Oncology School, Palermo, Italy 3 University of Brescia, Radiation Oncology, Brescia, Italy