Results: SBRT treatment: maximum small bowel and duodenum dose-volume constraints were exceeded in 5/30 (16.7%) and 2/30 (6.7%), respectively. Dose to OARs was: small bowel: Dmax 31.5-40.5 Gy, V30 0.2-13.4 cc; duodenum: Dmax 35.7-36.6 Gy, V30 2.1-3.7 cc. SBRS treatment: maximum small bowel and duodenum dosevolume constraints were exceeded in 2/21 patients (9.5%) and 1/21 patient (4.7%), respectively. Dose to OARs was: small bowel: Dmax 15.6-16.3 Gy, V12 1.7-8.5 cc; duodenum Dmax 16.0 Gy, V12

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... cc. With a median follow up of 24 months after SBRT and 18 months after SBRS, no early or late severe toxicity was observed in patients in whom constraints were not respected. Conclusion: Patients irradiated on small bowel and duodenum did not develop severe toxicity although the administered doses were above constrains proposed in literature. A prolonged follow-up and a larger population are needed to confirm the safety of dose-volume constraints other than those reported in literature about SBRT and SBRS on abdominal area. PO-0773 Reirradiation by extracranial stereotactic treatment: preliminary results of a dose escalation study F. Deodato Purpose or Objective: To define the maximum tolerated dose (MTD) of extra-cranial stereotactic treatment (SBRT) in previously irradiated patients.