Intraoperative radiotherapy (IORT) is an innovative treatment approach that has been tested in several Phase 1-11 studies and small Phase 111 trials in patients with resectable and unresectable pancreatic cancer. The technical approach and dose guidelines for adjacent normal tissues have been established in a series of experiments using a large animal (canine) model. This article reviews the experimental and clinical studies of IORT in cancer of the pancreas. Cancer 1996; 78:598-604. 8 1996 Aiiiericnn Cancer Society.
ntraoperative radiotherapy (IORT) is an innovative treatment ap-I proach to cancer of the pancreas in which a large single dose (>lo-15 Gray [Gy]) of radiation is delivered to either the resected tumor bed and draining lymphatics or to an unresectable tumor. This treatment approach allows for a theoretic increase in the therapeutic gain of radiation when comparing pancreatic tumor with dose-limiting adjacent normal tissues for, at least, three reasons: 1) the biologic effectiveness of a single large radiation dose is higher than that for the same dose given in a fractionated regimen; 2) the radiation is precisely delivered to the area at greatest risk of tumor recurrence (or persistence); and 3) irradiation of dose-limiting normal tissues, such as the bile duct, small bowel, stomach, and spinal cord, may be avoided by operative mobilization of the normal tissues (e.g., stomach, small bowel) from the treatment volume, by customized lead shielding to protect normal tissues within the field ( e g , bile duct stump prior to anastomosis), or by judicious use of electron beam energies to limit the radiation dose to deep structures (e.g., spinal cord). Electrons are generally used for IORT because of the sharp dose falloff of 6-18 Mev electrons typically selected for treatment of pancreatic cancer. IORT alone may be used as adjuvant therapy in resected pancreatic cancer, whereas it is typically combined with external beam radiation therapy (45-50 Gy/5 weeks) 2 5-fluorouracil (5-FUl-based chemotherapy given either pre-or postoperatively for patients with locally advanced unresectable disease.
Over the last 15-20 years, we and others have accumulated a considerable amount of experimental and clinical data on the use of IORT in cancer in the pancreas. This article will summarize these experimental and clinical trials of IORT.