How should we describe the radioblologic effect of extracranial stereotactic radlosurgery: equivalent uniform dose or tumor control probability?

Extracranial stereotactic radiosurgery (ESR) is now undergoing clinical investigation at numerous institutions as a treatment for solitary malignant lesions. Because there is no standard ESR technique, the same minimum dose might be applied through widely variable target dose-volume histograms. For multicenter trials of ESR or interinstitutional comparisons, a reliable index of radiobiological dose equivalency might facilitate the evaluation of dose-response relationships. Equivalent uniform dose (EUD) and tumor control probability (TCP) were considered for this application. While EUD appears more robust for the prospective description of ESR, TCP is expected to remain more valuable for a post hoc estimation of radiosensitivity parameters.

Use of computed tomography for the fabrication of a custom brachytherapy carrier: a clinical report

Early methods of fabricating customized radiation carriers for inaccessible areas, such as the nasopharyngeal space, normally required the patient to be under conscious sedation or general anesthesia to allow impressions for indirect processing techniques. This article describes the use of computed tomography to design and fabricate a carrier for the intracavity application of iodine 125 seeds for a patient with rhabdomyosarcoma of the nasopharynx. With tomography printed copies, a wax pattern was formed, flasked, boiled out, and eventually replaced with silicone material. The patient had to be available only for a conventional thin-cut computed tomography scan without contrast; no fitting appointments or anesthesia were necessary. The indirect procedure eliminated discomfort from impression making and allowed for precise fabrication of the nasopharyngeal carrier. The described technique can be used for other intracavitary radiation applications.

Brachytherapy for the prevention of stenosis in a canine hemodialysis graft model: preliminary observations

PURPOSE

To determine whether gamma brachytherapy can prevent in-stent stenosis in hemodialysis grafts.

MATERIALS AND METHODS

Six-millimeter polytetrafluoroethylene arteriovenous grafts were created bilaterally in six dogs. After 1 month, Wallstents spanning the venous anastomosis were placed to accelerate restenosis. Gamma irradiation (12 Gy) was delivered endoluminally to one of the two grafts by using an iridium 192 source; thus, each animal served as its own control. Fistulography was performed monthly for 10 months or until graft thrombosis, with measurement of stenosis at each time point. At the conclusion of the study period, the treated area was examined histologically, and a computer model was used to calculate the volume of intimal hyperplasia.

RESULTS

Delayed stent migration resulted in exclusion of one dog. In the remaining five dogs; maximum stenosis across all time intervals was less for the treated side (P < .04), and the volume of intimal hyperplasia was less for the treated side (P < .045). In one animal studied at 1 year, this trend reversed in terms of percentage stenosis but not total neointimal volume.

CONCLUSION

Brachytherapy with 192Ir (gamma) delivered at the time of stent placement reduces restenosis in this hemodialysis graft model, but, depending on the parameter evaluated (stenosis vs total volume of neointima), the benefit may wane or even reverse with time.

Wound complications associated with brachytherapy for primary or salvage treatment of head and neck cancer

Brachytherapy can be employed in the primary or salvage treatment of head and neck cancer. The advantage of brachytherapy is the stereotactic limitation of radiation exposure to noninvolved tissues. Wound complications associated with brachytherapy have been discussed only sporadically in the literature. This retrospective study examines 28 patients, 20 for initial treatment and eight for salvage, with varying site and stage head and neck cancer treated with brachytherapy in addition to external beam radiation therapy and/or surgery. The overall complication rate was 50% (14/28), with infection and minor flap breakdown being the most common problems. Tumor site in the primary treatment group was the only significant factor in wound complications. In the salvage group complications were minor and primarily related to flap coverage of brachytherapy catheters.

Radiation therapy of external iliac lymph nodes with lateral pelvic portals: identification of patients at risk for inadequate regional coverage

PURPOSE

To determine whether "standard" lateral pelvic radiation therapy portals provide adequate margins for treating the external iliac lymph nodes (EILNs).

MATERIALS AND METHODS

With computed tomographic (CT) data and a computerized algorithm, the course of the EILN chain was reconstructed in 48 patients. The marginal distance between a consistently localized portion of the EILNs and the anterior field border that was placed at the front of the pubic symphysis was recorded for each patient.

RESULTS

The EILNs were covered adequately in only 50% of both men and women. More adequate EILN margins were observed in (a) women older than 68 years, (b) women with small anteroposterior separations, (c) men older than 70 years, and (d) men and women with a low central obesity index. Less adequate margins were observed in men who were obese or men with large anteroposterior separations. In the study population, no correlation was observed for sex, race, or tumor site.

CONCLUSION

The authors recommend portals that are designed specifically for patients rather than standard portals that may inadequately cover the intended targets.