International journal of radiation oncology, biology, physics
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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, and function relationships in parotid salivary glands following conformal and intensity-modulated irradiation of head and neck cancer.
To determine the relationships between the three-dimensional dose distributions in parotid glands and their saliva production, and to find the doses and irradiated volumes that permit preservation of the salivary flow following irradiation (RT). ⋯ Dose/volume/function relationships in the parotid glands are characterized by dose and volume thresholds, steep dose/response relationships when the thresholds are reached, and a maximal volume dependence parameter in the NTCP model. A parotid gland mean dose of < or =26 Gy should be a planning goal if substantial sparing of the gland function is desired.
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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.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
Effect of post-implant edema on the rectal dose in prostate brachytherapy.
To characterize the effect of prostate edema on the determination of the dose delivered to the rectum following the implantation of 125I or 103Pd seeds into the prostate. ⋯ The rectal surface dose determined by analysis of a post-implant CT scan of an 125I or 103Pd prostate seed implant depends upon the timing of the CT scan. The dose indicated by the CT scan on day 30 is typically at least 50% greater than that indicated by the CT scan on day 0. Because of this difference, it is important to keep the timing of the post-implant CT in mind when specifying dose thresholds for rectal morbidity.