The clinical application of a non-axial treatment plan for pancreatic and biliary malignancies

Standard radiation therapy for adenocarcinoma of the pancreas treats a substantial portion of the renal parenchyma. It was hypothesized that rotating the plane of treatment to a non-axial orientation, with the anterior field entering the patient from an inferior oblique direction, would decrease the renal dose of radiation without increasing the liver dose or compromising the target dose. To test this hypothesis, patients referred for radical radiation treatment for tumors of the pancreas or distal common bile duct were prospectively evaluated by performing treatment planning using axial and non-axial field arrangements. Treatment plans were compared using dose volume histograms (DVHs) of both kidneys and the liver. In all 15 cases analyzed, the non-axial plan was superior to the axial plan with respect to renal dose, without significantly increasing the hepatic dose and was used for treatment. Treatment was not significantly more complex nor was gastrointestinal toxicity increased. These findings show that non-axial field arrangements can be used on a routine basis to decrease the renal dose of radiation for the treatment of pancreatic and biliary malignancies. It is anticipated that in the future, a combination of DVH-guided treatment planning and sophisticated renal function studies will be necessary to permit a more accurate prediction of the probability of renal complications resulting from radiation therapy.