International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 1997
A numerical simulation of organ motion and daily setup uncertainties: implications for radiation therapy.
In radiotherapy planning, the clinical target volume (CTV) is typically enlarged to create a planning target volume (PTV) that accounts for uncertainties due to internal organ and patient motion as well as setup error. Margin size clearly determines the volume of normal tissue irradiated, yet in practice it is often given a set value in accordance with a clinical precedent from which variations are rare. The (CTV/PTV) formalism does not account for critical structure dose. We present a numerical simulation to assess (CTV) coverage and critical organ dose as a function of treatment margins in the presence of organ motion and physical setup errors. An application of the model to the treatment of prostate cancer is presented, but the method is applicable to any site where normal tissue tolerance is a dose-limiting factor. ⋯ Monte Carlo-based treatment simulation is an effective means of assessing the impact of organ motion and daily setup error on dose delivery via external beam radiation therapy. Probability of Prescription Dose (PoPD) isosurfaces are a useful tool for the determination of nonuniform beam margins that reduce dose delivered to critical organs while preserving CTV dose coverage. Nonuniform fluence profiles can further alter critical organ dose with potential therapeutic benefits. Clinical consequences of this latter approach can only be assessed via clinical trials.
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Int. J. Radiat. Oncol. Biol. Phys. · Dec 1996
Clinical TrialHyperfractionated craniospinal radiotherapy and adjuvant chemotherapy for children with newly diagnosed medulloblastoma and other primitive neuroectodermal tumors.
This single-institution Phase III study conducted from 1989 to 1995 evaluates the feasibility of a multimodality protocol combining hyperfractionated craniospinal radiotherapy (HFRT) followed by adjuvant chemotherapy in 23 patients with newly diagnosed primitive neuroectodermal tumors (PNET) arising in the central nervous system. ⋯ This multimodality protocol is feasible in the short term, and long-term monitoring of neurocognitive and neuroendocrine effects are in progress. Excellent long-term disease control has been achieved for medulloblastoma patients with high T stages who were M0 at diagnosis (Group 1), the majority of whom had gross total resections. This group has a progression-free survival of 95% after a median period of follow-up of 6.5 years. Alternative treatment strategies must be developed for patients with high M stages, as five of seven patients died of progressive or recurrent disease.
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Int. J. Radiat. Oncol. Biol. Phys. · Nov 1996
Myocardial damage in breast cancer patients treated with adjuvant radiotherapy: a prospective study.
To look for early and late signs of cardiac side effects of postoperative radiotherapy in patients with left-sided breast cancer. ⋯ In this study half of the patients exhibited new scintigraphic defects that indicate radiation-induced myocardial damage, probably affecting the microcirculation. There were no changes on electrocardiography or any deterioration of the left ventricular function at this stage. Long-term follow-up is necessary to assess whether this finding is a prognostic sign for developing radiation-induced coronary artery disease.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1996
Conformal irradiation of the prostate: estimating long-term rectal bleeding risk using dose-volume histograms.
Dose-volume histograms (DVHs) may be very useful tools for estimating probability of normal tissue complications (NTCP), but there is not yet an agreed upon method for their analysis. This study introduces a statistical method of aggregating and analyzing primary data from DVHs and associated outcomes. It explores the dose-volume relationship for NTCP of the rectum, using long-term data on rectal wall bleeding following prostatic irradiation. ⋯ There is a dose-volume relationship for rectal mucosal bleeding in the region between 60 and 75 CGE; therefore, efforts to spare rectal wall volume using improved treatment planning and delivery techniques are important. Stratifying dose-volume histograms (DVHs) into risk groups, as done in this study, represents a useful means of analyzing empirical data as a function of hetereogeneous dose distributions. Modeling efforts may extend these results to more heterogeneous treatment techniques. Such analysis of DVH data may allow practicing clinicians to better assess the risk of various treatments, fields, or doses, when caring for an individual patient.