International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Dec 2003
Assessment of different IMRT boost delivery methods on target coverage and normal-tissue sparing.
Because of biologic, medical, and sometimes logistic reasons, patients may be treated with 3D conformal therapy or intensity-modulated radiation therapy (IMRT) for the initial treatment volume (PTV(1)) followed by a sequential IMRT boost dose delivered to the boost volume (PTV(2)). In some patients, both PTV(1) and PTV(2) may be simultaneously treated by IMRT (simultaneous integrated boost technique). The purpose of this work was to assess the sequential and simultaneous integrated boost IMRT delivery techniques on target coverage and normal-tissue sparing. ⋯ For equal PTV coverage, both sequential-IMRT techniques demonstrated moderately improved sparing of the critical structures. SIB-IMRT, however, markedly reduced doses to the critical structures for most of the cases considered in this study. The conformality of the SIB-IMRT plans was also much superior to that obtained with both sequential-IMRT techniques. The improved conformality gained with SIB-IMRT may suggest that the dose to nontarget tissues will be lower.
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Int. J. Radiat. Oncol. Biol. Phys. · Dec 2003
Hypofractionated conformal radiotherapy in carcinoma of the prostate: five-year outcome analysis.
Recent publications have indicated that the alpha/beta ratios for carcinoma of the prostate are much lower than had originally been thought, suggesting that prostate cancer may be highly sensitive to fraction size. We have reviewed our unique experience of the use of 3.13 Gy fractions in a large cohort of men treated homogeneously in a single institute. ⋯ These data indicate that the delivery of a relatively low total dose using a hypofractionated regime results in similar tumor control and normal-tissue toxicity to 65-70 Gy delivered in 1.8-2 Gy fractions. These data suggest that this is an acceptable regime for good-prognosis patients. However, because of the evidence for a dose effect at doses above 70 Gy with "conventional fractionation," we are now treating intermediate- and poor-risk patients within a hypofractionated dose escalation trial to 60 Gy in 20 fractions using intensity- modulated radiotherapy.
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Int. J. Radiat. Oncol. Biol. Phys. · Dec 2003
Reproducibility of lung tumor position and reduction of lung mass within the planning target volume using active breathing control (ABC).
The active breathing control (ABC) device allows for temporary immobilization of respiratory motion by implementing a breath hold at a predefined relative lung volume and air flow direction. The purpose of this study was to quantitatively evaluate the ability of the ABC device to immobilize peripheral lung tumors at a reproducible position, increase total lung volume, and thereby reduce lung mass within the planning target volume (PTV). ⋯ Results from this study indicate that there remains some inter-breath hold variability in peripheral lung tumor position with the use of ABC inspiration breath hold, which prevents significant PTV margin reduction. However, lung volumes can significantly increase, thereby decreasing the mass of lung within a standard PTV.