The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for head-and-neck carcinoma.

PURPOSE: To develop recommendations for use of high-dose-rate (HDR) brachytherapy in patients with head-and-neck cancer. METHODS: A panel consisting of members of the American Brachytherapy Society (ABS) performed a literature review, added information based upon their clinical experience, and formulated recommendations for head-and-neck HDR brachytherapy. RESULTS: The ABS recommends the use of brachytherapy as a component of the treatment of head-and-neck tumors. However, the ABS recognizes that some radiation oncologists are reluctant to employ brachytherapy in the head-and-neck region because of the complexity of the postoperative management and concerns about radiation safety. In this regard, HDR eliminates unwanted radiation exposure and thereby permits unrestricted delivery of clinical care to these brachytherapy patients. The ABS made specific recommendations for previously untreated and recurrent head-and-neck cancer patients on patient selection criteria, implant techniques, target volume definition, and HDR treatment parameters (such as time, dose, and fractionation schedules). Suggestions were provided for treatment with HDR alone and in combination with external beam radiation therapy. It should be recognized that only limited experiences exist with HDR brachytherapy in patients with head-and-neck cancers. Therefore, some of these suggested doses have not been extensively tested in clinical practice. Hence, these guidelines will be updated as significant new outcome data are available. Any clinician following these guidelines is expected to use clinical judgment to determine an individual patient's treatment. CONCLUSIONS: Little has been published in the clinical literature on HDR brachytherapy in head-and-neck cancer. Based upon the available information and the clinical experience of the panel members, general and site-specific recommendations were offered. Areas for further investigations were identified.

Dosimetric considerations of commercially fabricated esophageal applicators.

Two commercially fabricated esophageal applicators for low dose rate intraluminal brachytherapy were compared using the dose non-uniformity ratio (DNR). One of the applicators has a single afterloading catheter while the other applicator has six afterloading catheters to accommodate low dose rate 192Ir ribbon or wire sources. Five sets of source configurations, each with a different ribbon length in the range of 5-17 cm were analysed using the DNR. The DNR shows the delivery of relatively higher total doses at higher dose rates to tissues closer to the applicators. The difference in the inhomogeneity of dose rates and the treatment volume exposed to higher dose rates than the prescribed dose rate between the two applicators are minimal. The dose homogeneity is better for the single-source applicator while the worst dose homogeneity for the six-source applicator is caused by the placement of each source closer to the surface of the applicator. The implications of higher dose rates were discussed using the alpha/beta model.

Megavoltage external beam irradiation of craniopharyngiomas: analysis of tumor control and morbidity.

From 1971 to 1985, 21 patients received megavoltage external beam radiation therapy at the University of Pittsburgh for control of craniopharyngioma. Minimum tumor doses prescribed to the 95% isodose volume ranged between 51.3 to 70.0 Gy. Median total dose was 60.00 Gy and median dose per fraction was 1.83 Gy. Three deaths occurred from intercurrent disease and no deaths from tumor progression. Actuarial overall survival was 89% and 82% at 5 and 10 years. Actuarial local control was 95% at 5 and 10 years. Radiation related complications included one patient with optic neuropathy, one with brain necrosis, and one that developed optic neuropathy followed by brain necrosis. The high dose group of patients who received a NSD or Neuret equivalent of greater than 60 Gy at 1.8 Gy per fraction had a significantly greater risk of radiation complications (p = .024). The actuarial risk at 5 years for optic neuropathy was 30% and brain necrosis was 12.5% in the high dose group. Tumor control in the high dose group was not shown to be significantly better. Any possible benefit in tumor control in treating patients with craniopharyngioma with doses above 60 Gy at 1.8 Gy per fraction appears to be offset by the increased risk of radiation injury.

Verification of electron beam therapy with storage phosphor images: precision of field placement.

Portal verification images were generated from the photon contamination in electron beams produced by a linear accelerator during treatment of patients receiving high-energy electron radiation therapy (8-14 MeV). An experimental storage phosphor system was used to record the images and display them on laser-printed film. Images were obtained from four or more treatment fractions from 21 cases of head and neck cancer. Precision in field placement was estimated by determining the position of a selected anatomic landmark relative to the center of the field for each series of images. The average standard deviation in the field-position measurements was 3.8 mm. Several procedural problems were also detected and corrected after review of the verification images. The results indicate that the emphasis placed on monitoring and control of field-positioning error in high-energy electron treatments should be similar to the emphasis placed on this aspect of error in photon treatment.

Nasopharyngeal impression technique for fabrication of a radiation carrier.

A new technique for intracavitary application of Iridium 192 seeds in carcinoma of the nasopharynx is described. This technique allows for accurate construction of a nasopharyngeal carrier that permits the radiotherapist to deliver an adequate dose of irradiation to the nasopharynx.