Combined isodose curves of high-dose rate interstitial brachytherapy with external-beam radiation therapy in pancreatic carcinoma.

From September 1989 until March 1992 nine patients with unresectable, though localized carcinoma of the pancreas were treated by a multimodality therapy consisting of palliative surgery, interstitial conformal brachytherapy in high-dose rate mode (HDRBT) with iridium-192 up to 30 Gy and external-beam radiation therapy (EBRT) of about 52 Gy. Four patients simultaneously received two cycles of chemotherapy consisting of 5-FU and Leucovorin. Since high radiation doses are applied which are not tolerated in adjacent healthy tissues, doses to tumor and critical areas need to be known precisely and are to be adjusted before treatment. A three-dimensional imaging system is required. A self developed method combines the data of simulation radiographs and those of CT scans. The prescribed minimum target absorbed dose in HDRBT is adjusted to the target volume sparing organs at risk. The specialized quality assurance is adapted to this method. Differences between measured and calculated doses do not exceed 5%. The addition of isodoses of HDRBT and EBRT on CT scans is demonstrated. Due to patients' selection the treatment concept did not reveal any positive effects on survival. However, excellent palliative results were obtained without severe side-effects.