ESTRO 36 Abstract Book

S225 ESTRO 36 _______________________________________________________________________________________________

Italy 5 University of Bologna, Department of Medical and Surgical Sciences - DIMEC, Bologna, Italy 6 University of Bologna- S. Orsola-Malpighi Hospital, Department of Oncology, Bologna, Italy 7 Università Cattolica S. Cuore, Department of Surgery, Rome, Italy 8 Hospital General Universitario Gregorio Marañón- Complutense University, Department of Oncology, Madrid, Spain 9 University of Virginia- Charlottesville, Department of Radiation Oncology, VA, USA 10 Mayo Clinic, Department of Radiation Oncology, Rochester, USA 11 S. Raffaele Scientific Institute, Department of Oncology, Milano, Italy 12 Fondazione Giovanni Paolo II, Unit of Radiotherapy- Unit of General Oncology, Campobasso, Italy 13 Fondazione Giovanni Paolo II, Unit of Medical Physics, Campobasso, Italy Purpose or Objective To evaluate the impact of radiation dose on overall survival (OS) in patients treated with adjuvant chemoradiation (CRT) for pancreatic adenocarcinoma (PAC). Material and Methods A multicenter retrospective analysis on 514 patients with PAC (T1-3; N0-1; M0) treated with surgical resection with macroscopically negative margins (R0-1) followed by adjuvant CRT was performed. Exclusion criteria included metastatic or unresectable disease at surgery, intraoperative radiotherapy (IORT), macroscopic residual disease (R2), postoperative death (within 60 days after surgery) and histological diagnosis different from ductal carcinoma. We analyzed patients stratifying them into 4 groups based on radiotherapy doses (group 1: < 45 Gy, group 2: ≥ 45 and < 50 Gy, group 3: ≥ 50 and < 55 Gy, group 4: ≥ 55 Gy). Adjuvant chemotherapy was prescribed to 141 patients. Survival functions were plotted using the Kaplan- Meier method and compared through the log-rank test. Clinical and pathological parameters associated with significant differences in OS at the univariate analysis were entered into a multivariable Cox model using a forward stepwise [Wald] strategy (p removal ≥ 0.10; p addition < 0.05) based on likelihood ratio test, in order to obtain a final model including only the subset of variables significant in predicting OS. All tests were two-sided and a p value < 0.05 was considered statistically significant. Results Median follow-up was 20 months (3-120). At univariate analysis a worse OS was recorded in patients with higher Ca19.9 levels (> 90 U/ml; p < 0.001), higher tumor grade (G3-4, p = 0.004), R1 resection (p = 0.004), higher pT stage (pT3-4. p = 0.002) and positive nodes (p < 0.001). Furthermore, patients receiving increasing doses of chemoradiation showed a significantly improved OS (Figure 1). In groups 1, 2, 3, and 4 median OS was 13.0 months, 21.0 months, 22.0 months, and 28.0 months, respectively (p=0.004). The significant impact of higher dose was confirmed by multivariate analysis (HR: 0.46, 95%CI: 0.27-0.78, p= 0.005).

Results SMART was delivered in 45 fractions in nine pts (4F, 5M; ages 55-87 yrs) with LAPC. Two pts had biliary stents. All pts were able to complete the BH delivery. Median duration of the SMART delivery was 54 min (range 42-73). With the video-feedback method, median gated treatment efficiency (ratio between actual beam-on time and delivery time) was 0.66 for all fractions, ranging from 0.40-0.92 (Fig 2). Pt follow-up is still limited, but early results show no grade ≥3 acute toxicity. Prospectively- scored patient reported outcomes revealed maximum Grade 2 fatigue and nausea in, respectively, 6 pts and 1 pt.

Conclusion SMART is novel treatment approach for LAPC that requires no placement of fiducials, and is well tolerated, even by elderly pts and those with stents. Initial experience revealed that delivery within a one hour time-frame per fraction is feasible. Updated clinical follow-up data will be presented. OC-0426 Adjuvant chemoradiation in pancreatic cancer: impact of radiotherapy dose on survival A.G. Morganti 1 , M. Falconi 2 , G.C. Mattiucci 3 , A. Arcelli 1,4 , F. Bertini 1 , A. Farioli 5 , A. Guido 1 , M.C. Di Marco 6 , L. Fuccio 5 , S. Alfieri 7 , F.A. Calvo 8 , B.W. Maidment 3rd 9 , R.C. Miller 10 , M. Reni 11 , G. Macchia 12 , F. Deodato 12 , S. Cilla 13 , G. Di Gioia 12 , F. Cellini 3 , V. Valentini 3 1 University of Bologna- S. Orsola-Malpighi Hospital, Radiation Oncology Center- Department of Experimental- Diagnostic and Speciality Medicine- DIMES, Bologna, Italy 2 San Raffaele Hospital, Department of Surgery- Pancreatic Surgery Unit, Milano, Italy 3 Università Cattolica S. Cuore, Department of Radiotherapy, Rome, Italy 4 Ospedale Bellaria, Radiotherapy Department, Bologna,