International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2002
Comparative StudyPrognostic significance of race on biochemical control in patients with localized prostate cancer treated with permanent brachytherapy: multivariate and matched-pair analyses.
To compare PSA relapse-free survival (PSA-RFS) between African-American (AA) and white American (WA) males treated with permanent prostate brachytherapy (PPB) for clinically localized prostate cancer. ⋯ Race is not an independent predictor of 5-year PSA-RFS in patients with localized prostate cancer treated with PPB. This result is consistent with other studies that also show that race does not contribute to differences in outcome after definitive therapies for localized prostate cancer.
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2002
Relative biological effectiveness (RBE) values for proton beam therapy.
Clinical proton beam therapy has been based on the use of a generic relative biological effectiveness (RBE) of 1.0 or 1.1, since the available evidence has been interpreted as indicating that the magnitude of RBE variation with treatment parameters is small relative to our abilities to determine RBEs. As substantial clinical experience and additional experimental determinations of RBE have accumulated and the number of proton radiation therapy centers is projected to increase, it is appropriate to reassess the rationale for the continued use of a generic RBE and for that RBE to be 1.0-1.1. ⋯ At present, there is too much uncertainty in the RBE value for any human tissue to propose RBE values specific for tissue, dose/fraction, proton energy, etc. The experimental in vivo and clinical data indicate that continued employment of a generic RBE value and for that value to be 1.1 is reasonable. However, there is a local "hot region" over the terminal few millimeters of the SOBP and an extension of the biologically effective range. This needs to be considered in treatment planning, particularly for single field plans or for an end of range in or close to a critical structure. There is a clear need for prospective assessments of normal tissue reactions in proton irradiated patients and determinations of RBE values for several late responding tissues in laboratory animal systems, especially as a function of dose/fraction in the range of 1-4 Gy.
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2002
Clinical TrialClinical implementation of intensity-modulated arc therapy.
Intensity-modulated arc therapy (IMAT) is a method for delivering intensity-modulated radiation therapy (IMRT) using rotational beams. During delivery, the field shape, formed by a multileaf collimator (MLC), changes constantly. The objectives of this study were to (1) clinically implement the IMAT technique, and (2) evaluate the dosimetry in comparison with conventional three-dimensional (3D) conformal techniques. ⋯ Initial results demonstrated the feasibility and accuracy of IMAT for achieving highly conformal dose distributions for different sites. If treatment plans can be optimized for IMAT cone beam delivery, we expect IMAT to achieve dose distributions that rival both slice-based and fixed-field IMRT techniques. The efficient delivery with existing linac and MLC makes IMAT a practical choice.
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2002
Practical application of biochemical failure definitions: what to do and when to do it.
The posttreatment prostate-specific antigen (PSA) profile can often be difficult to interpret after external beam radiotherapy for prostate cancer. We performed an extensive analysis of post-radiotherapy PSA measurements to determine the clinical significance of biochemical failure (BF) and the correlation of BF with clinical failure (CF) and cause-specific death (CSD). ⋯ Once the post-radiotherapy PSA profile reaches >or=3 ng/ml above the nadir, there is a high risk of clinical failure within a relatively short time period, for which treatment intervention may be considered, regardless of pretreatment characteristics. After a nadir >or=1.0 ng/ml or three consecutive rises, some patients (especially with low-risk pretreatment characteristics) may be considered for further PSA observation before treatment intervention.
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2002
(IN)-efficacy of salvage radiotherapy for rising PSA or clinically isolated local recurrence after radical prostatectomy.
To determine the efficacy of external beam radiotherapy (RT) as salvage treatment for prostate-specific antigen (PSA) failure or local recurrence after radical prostatectomy. ⋯ The efficacy of salvage RT for PSA failure or local recurrence after RT was limited, reflected by very low relapse-free rates. Salvage RT appeared more efficacious for patients with a delayed PSA rise than for those with either persistently detectable postoperative PSA levels or clinically palpable local recurrence. Other strategies such as a combination of salvage RT and hormonal therapy need to be explored.