International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2006
Simultaneous beam geometry and intensity map optimization in intensity-modulated radiation therapy.
In current intensity-modulated radiation therapy (IMRT) plan optimization, the focus is on either finding optimal beam angles (or other beam delivery parameters such as field segments, couch angles, gantry angles) or optimal beam intensities. In this article we offer a mixed integer programming (MIP) approach for simultaneously determining an optimal intensity map and optimal beam angles for IMRT delivery. Using this approach, we pursue an experimental study designed to (a) gauge differences in plan quality metrics with respect to different tumor sites and different MIP treatment planning models, and (b) test the concept of critical-normal-tissue-ring--a tissue ring of 5 mm thickness drawn around the planning target volume (PTV)--and its use for designing conformal plans. ⋯ The MIP model described allows simultaneous optimization over the space of beamlet fluence weights and beam and couch angles. Based on experiments with tumor data, this approach can return good plans that are clinically acceptable and practical. This work distinguishes itself from recent IMRT research in several ways. First, in previous methods beam angles are selected before intensity map optimization. Herein, we employ 0/1 variables to model the set of candidate beams, and thereby allow the optimization process itself to select optimal beams. Second, instead of incorporating dose-volume criteria within the objective function as in previous work, herein, a combination of discrete and continuous variables associated with each voxel provides a mechanism to strictly enforce dose-volume criteria within the constraints. Third, using the construct of critical-normal-tissue-ring within the objective function can enhance the achievement of conformal plans. Based on the three tumor sites considered, it appears that volume and spatial geometry with respect to the PTV are important factors to consider when selecting objectives to optimize, and in estimating how well suited a particular model is for achieving a specified goal.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2006
Intensity-modulated radiation therapy (IMRT) for nasopharynx cancer: update of the Memorial Sloan-Kettering experience.
We previously demonstrated that intensity-modulated radiation therapy (IMRT) significantly improves radiation dose distribution over three-dimensional planning for nasopharynx cancer and reported positive early clinical results. We now evaluate whether IMRT has resulted in improved outcomes for a larger cohort of patients with longer follow-up. ⋯ The pattern of primary site failure within the target volume suggests locally advanced T stage disease may require a higher biologic dose to gross tumor. Rates of severe (Grade 3-4) ototoxicity and xerostomia are low with IMRT as a result of normal-tissue protection. Distant metastases are now the dominant form of failure, emphasizing the need for improved systemic therapy.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2006
Multicenter StudyPrognostic factors predicting functional outcomes, recurrence-free survival, and overall survival after radiotherapy for metastatic spinal cord compression in breast cancer patients.
To identify significant prognostic factors after irradiation of metastatic spinal cord compression (MSCC) in 335 breast cancer patients. ⋯ Outcomes and survival after RT for MSCC in breast cancer patients are associated with several prognostic factors. Patients with poor expected survival may be treated with shorter-course RT to keep the overall treatment time short. If survival is expected to be relatively favorable, longer-course RT appears preferable, because it is associated with fewer MSCC recurrences.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2006
Long-term results of high-dose conformal radiotherapy for patients with medically inoperable T1-3N0 non-small-cell lung cancer: is low incidence of regional failure due to incidental nodal irradiation?
To report the results of high-dose conformal irradiation and examine incidental nodal irradiation and nodal failure in patients with inoperable early-stage non-small-cell lung cancer (NSCLC). ⋯ Radiation dose is positively associated with overall survival in patients with medically inoperable T1-3N0 NSCLC, though long-term results remain poor. The nodal failure rate is low and does not seem to be due to high-dose incidental irradiation.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2006
The influence of isotope and prostate volume on urinary morbidity after prostate brachytherapy.
To evaluate the influence of isotope and prostate size on International Prostate Symptom Score (IPSS) normalization, catheter dependency, and the need for surgical intervention secondary to bladder outlet obstruction after prostate brachytherapy. ⋯ Regardless of prostate size, isotope did not impact IPSS resolution, catheter dependency, or the need for postbrachytherapy surgical intervention. Although prostate size did predict for short-term (<5 days) catheter dependency, it did not influence IPSS resolution or the need for surgical intervention.