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- Dose-response to different radiochemotherapy regimens in locally advanced pancreatic cancerPublication . Costa Ferreira, Brígida; Dias, Joana; Gomes, Adriana; Mavroidis, Panayiotis; Rocha, HumbertoConformal radiation therapy (RT) delivered concomitantly with chemotherapy including 5-fluorouracil (5-FU) or Gemcitabine (GEM) is a common treatment for patients with unresectable locally advanced pancreatic tumors. In this study, the Poisson model describing tumor response to these two treatment options was derived. Clinical data was retrieved from reports pub lished from 1990 to 2015. Dosimetric and clinical data from 1196 patients treated with RT with concurrent 5-FU or GEM were gathered. RT doses ranging from 3.6–64.8 Gy, delivered in fractions of 1.2–8 Gy, were converted to a 2 Gy fractionation scheme using the Biological Effective Dose concept. The param eters of the Poisson-Linear-Quadratic-Time model were derived using genetic algorithm optimization to minimize the least-square fitting error and a local search was then made using the maximum likelihood method. The goodness of the fit was assessed using the Pearson v2 -test. For RT+5-FU, D50 was 59.8 Gy, c was 1.3, a/b was 3.2, Tpot was 18.6 days and Tk was 25.0 days. For RT+GEM, D50 was 54.5 Gy, c was 1.4, a/b was 4.6, Tpot was 34.2 days and Tk was 37.2 days. As expected, RT+GEM showed higher efficacy than RT+5-FU. A RT dose-response effect was obtained showing that treatment strategies allowing a dose-escalation in pancreas tumors should be investigated