Twenty-two patients were irradiated using two different dose schedules of intracavitary irradiation for palliation of locally advanced or metastatic carcinoma of the esophagus. Irradiation was given solely with either manually afterloaded low/intermediate dose Cesium-137 (LDR) or high dose rate Iridium-192 (HDR) delivered via remote afterloader. This study was designed to test the effectiveness of HDR intracavitary brachytherapy in the relief of dysphagia and the maintenance of esophageal patency and to compare with our previous experiences with LDR intracavitary brachytherapy. Accelerated treatments were especially suited for patients with poor physical condition or short life expectancy unlikely to complete a full course of external beam irradiation without treatment interruption. Two thousand cGY in three fractions of LDR was compared with 1,250 cGY in one fraction HDR with essentially equal results.
High dose rate (HDR) remote afterloading is increasingly being used to replace many conventional low dose rate (LDR) brachytherapy procedures. Implementation of the microSelectron-HDR with Ir-192 at our facility necessitated this study to obtain equivalent dosimetric distributions with those of our LDR Cs-137 techniques using our current treatment planning system. Three anatomical sites are presented: nasopharynx, esophagus, and uterine cervix. Attention must be given to the anisotropy of Cs-137 tubes when converting to Ir-192; for linear geometries, total equivalent activity may be preserved but the shapes of the resulting isodose curves for Ir-192 are longer than those of Cs-137. In the case of Fletcher-Suit intracavitary treatments of the uterine cervix, the longer contours for Ir-192 in the vaginal ovoids results in higher isodose levels reaching the bladder and rectum. Maintaining the traditional dose levels to these organs is accomplished by modifying the loading of the ovoids to approximately 85% of the corresponding Cs-137 activity. Computerized dosimetry is presented, along with a chart we have devised to easily convert a standard LDR treatment to HDR dwell times. Our results are especially suitable to those users who will continue to make use of their present computer treatment planning system.
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