THE ANALYSIS OF DOSES FOR KIDNEY, LIVER AND MEDULLA SPINALIS WITH RESPECT TO DOSE-VOLUME HISTOGRAMS IN PANCREATIC AND STOMACH CANCER TREATED WITH CHEMORADIOTHERAPY

Kidneys and liver are considered dose-limiting organs for upper abdominal malignancies, although radiation hepatitis and renal failure are rare after irradiation of pancreatic and stomach cancers. The purpose of this work was to evaluate kidney, liver, spinal cord doses with respect to dose volume histograms (DVH), and kidney volume received more than 24 Gy (with the 3-D dose distributions) in pancreatic and stomach cancer treated with conventional techniques to a dose of 46-54 Gy. Eight pancreatic carcinomas and 3 stomach cancers treated in our institution were enrolled in this study. The kidneys and tumor were drawn on simulation films using computed tomography images and at least 60% of one kidney was spared with customized blocks. Diagnostic images were transferred to Plato planning system and kidneys, liver, spinal cord and GTV were contoured for each patient. Two dimensional computerized dose distributions were achieved with 25-MV x-ray beams and crude dose statistics were extracted from generated DVH data. The DVH statistical analysis helped us to analyze percentage of kidney volume receiving doses above and below 24 Gy. When conventionally calculated (two-dimensional) non-spared kidney percentages were compared with V25 values (volume receiving 25 Gy or more) derived from DVH statistics, the difference was not statistically significant for both right and left kidney (p= 0.8 and p=0.4, respectively). The three dimensional calculation in addition to traditional two-dimensional evaluations provided more reliable quantitative estimation of boost dose contribution to critical structures.

Keywords: pancreatic cancer, stomach cancer, kidney, dose-volume histograms