International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
Deep inspiration breath-hold technique for lung tumors: the potential value of target immobilization and reduced lung density in dose escalation.
This study evaluates the dosimetric benefits and feasibility of a deep inspiration breath-hold (DIBH) technique in the treatment of lung tumors. The technique has two distinct features--deep inspiration, which reduces lung density, and breath-hold, which immobilizes lung tumors, thereby allowing for reduced margins. Both of these properties can potentially reduce the amount of normal lung tissue in the high-dose region, thus reducing morbidity and improving the possibility of dose escalation. ⋯ Patients tolerate DIBH maneuvers well and can perform them in a highly reproducible fashion. Compared to conventional free-breathing treatment, the DIBH technique benefits from reduced margins, as a result of the suppressed target motion, as well as a decreased lung density; both contribute to moving normal lung tissue out of the high-dose region. Because less normal lung tissue is irradiated to high dose, the possibility for dose escalation is significantly improved.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
Use of the RTOG recursive partitioning analysis to validate the benefit of iodine-125 implants in the primary treatment of malignant gliomas.
To date, numerous retrospective studies have suggested that the addition of brachytherapy to the conventional treatment of malignant gliomas (MG) (surgical resection followed by radiotherapy +/- chemotherapy) leads to improvements in survival. Two randomized trials have suggested either a positive or no survival benefit with implants. Critics of retrospective reports have suggested that the improvement in patient survival is due to selection bias. A recursive analysis by the RTOG of MG trials has stratified MG patients into 6 prognostically significant classes. We used the RTOG criteria to analyze the implant data at Wayne State University to determine the impact of selection bias. ⋯ When applied to MG patients receiving permanent I-125 implant, the criteria of the RTOG recursive partitioning analysis are a valid tool to define prognostically distinct survival groups. As reflected in the RTOG study, a downward survival trend for the implant patients is seen from "best to worse" class patients. Compared to the RTOG database, median survival achieved by the addition of implant is improved most demonstrably for the poorer prognostic classes. This would suggest that selection bias alone does not account for the survival benefit seen with I-125 implant and would contradict the notion that the patients most eligible for implant are those gaining the most benefit from the treatment. In light of the contradictory results from two randomized studies and given the present results, further randomized studies with effective stratification are required since the evidence for a survival benefit with brachytherapy (as seen in retrospective studies) is substantial.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
Lack of effect of tumor size on the prognosis of carcinoma of the uterine cervix Stage IB and IIA treated with preoperative irradiation and surgery.
The purpose of this analysis was to evaluate the prognostic significance of cervical tumor size in patients with Stages Ib and IIa carcinoma of the cervix treated with preoperative irradiation and radical or conservative hysterectomy. ⋯ For this population of patients treated with preoperative irradiation and surgery, pelvic lymph node status at the time of hysterectomy and the preoperative irradiation dose to the pelvic lymph nodes are independent predictors of progression-free survival and the development of distant metastasis. The pretreatment cervical tumor size is of less importance for predicting progression-free survival and the development of distant metastasis but clinical stage is an important prognostic variable. These results are in contrast with those of surgery or irradiation alone, in which primary tumor size is a critical prognostic factor for all outcome parameters.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
Dose-volume analysis for quality assurance of interstitial brachytherapy for breast cancer.
The use of brachytherapy in the management of breast cancer has increased significantly over the past several years. Unfortunately, few techniques have been developed to compare dosimetric quality and target volume coverage concurrently. We present a new method of implant evaluation that incorporates computed tomography-based three-dimensional (3D) dose-volume analysis with traditional measures of brachytherapy quality. Analyses performed in this fashion will be needed to ultimately assist in determining the efficacy of breast implants. ⋯ Preliminary results using our new technique to evaluate implant quality with CT-based 3D dose-volume analysis appear promising. Dosimetric quality and target volume coverage can be concurrently analyzed, allowing the possibility of evaluating implants prospectively. Considering that target volume coverage may be suboptimal even after radiographically verifying accurate implant placement, techniques similar to this need to be developed to ultimately determine the true efficacy of brachytherapy in the management of breast cancer.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
The importance of adequate follow-up in defining treatment success after external beam irradiation for prostate cancer.
We reviewed our institution's experience treating patients with localized prostate cancer with external beam radiation therapy (RT) to determine how differences in the length of follow-up affect the determination of treatment outcome using the American Society for Therapeutic Radiology and Oncology (ASTRO) Consensus Panel Definition of biochemical failure (BF). ⋯ When the ASTRO Consensus Panel definition of BF is used to calculate treatment success with external beam RT for prostate cancer, adequate follow-up is critical. Depending upon the length of time after treatment, significantly different rates of BC (varying by 15% to 30%) can be calculated for the same time interval chosen for analysis. These results suggest that data should only be reported if the length of follow-up extends at least beyond the time point at which actuarial results are examined for the majority of patients.