International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2004
Characterization of rectal normal tissue complication probability after high-dose external beam radiotherapy for prostate cancer.
Conformal radiotherapy (RT) has allowed radiation dose escalation to improve the outcome of prostate cancer. With higher doses, concern exists that rectal injury may increase. This study analyzed the utility and limitations of the widely used Lyman-Kutcher- Burman (LKB) normal tissue complication probability model in projecting the hazards of rectal complication with high-dose RT. ⋯ Our analysis suggests a dose response for rectal bleeding probability along with a volume effect. We found that the LKB model might have limited utility in determining a large volume effect. We further suggest that LKB model should be used with caution in clinical practice.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2004
Can concomitant-boost accelerated radiotherapy be adopted as routine treatment for head-and-neck cancers? A 10-year single-institution experience.
Accelerated schedules are effective in overcoming repopulation during radiotherapy (RT) for head-and-neck cancers, but their feasibility is compromised by increased toxicity. The therapeutic ratio may be particularly favorable for 5-week regimens. This study reports the 10-year experience of a single institution in the routine use of concomitant boost RT as standard radical treatment in all but the most favorable stage patients. ⋯ The present, moderately accelerated, concomitant boost regimen is logistically feasible, causing minimal inconvenience to the technical staff and yielding a high rate of patient compliance. Concomitant chemotherapy administration is feasible provided that patients are carefully selected and supportive care is introduced in a timely fashion. Considering the manageable toxicity and the satisfactory tumor control obtained, this regimen represents a good choice when considering implementation of an altered RT fractionation schedule as standard treatment for head-and-neck cancers.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2004
Necessity for adjuvant neck dissection in setting of concurrent chemoradiation for advanced head-and-neck cancer.
Neck dissection has traditionally played an important role in the treatment of patients with squamous cell carcinoma of the head and neck who present with regionally advanced neck disease (N2-N3). Radiotherapy and concurrent chemotherapy improves overall survival in advanced head-and-neck cancer compared with radiotherapy alone. The necessity for postchemoradiation neck dissection is controversial. The intent of this report was to define the value of neck dissection in this patient population better. ⋯ The clinical and pathologic responses in the neck correlated poorly with one another for patients with N2-N3 neck disease undergoing concurrent chemoradiation for advanced head-and-neck cancer. MND still appears to confer a disease-free survival and overall survival advantage with acceptably low morbidity. Tumor oxygenation assessment may be useful in selecting patients who are especially prone to have residual disease. Better tools need to be developed to determine prospectively whether this procedure is required for individual patients.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2004
Dose-volume conundrum for response of prostate cancer to brachytherapy: summary dosimetric measures and their relationship to tumor control probability.
Although it is known that brachytherapy dose distributions are highly heterogeneous, the effect of particular dose distribution patterns on tumor control probability (TCP) is unknown. It is unlikely that clinical results will throw light on the question in the near future, given the long follow-up and detailed dosimetry required for each patient. We used detailed dose distribution data from 50 patients combined with radiobiologic parameters consistent with what is known about TCP curves for prostate cancer to study the changes in TCP that accompany gross dosimetric measures and particular dosing irregularities (e.g., moderate underdosing of large volumes vs. extreme underdosing of small volumes). ⋯ The work described here was an hypothesis-generating study. Our results showed that even if the V100 and D90 are nearly identical for 2 patients, there can be (and frequently are) significant differences in the dose distributions in the subvolumes of the prostate. Under simulated dose-response conditions (i.e., with variations in the dose distribution), the D90 and minimal dose significantly affected the TCP but the V100 and the volumes moderately or severely underdosed did not. In general, one must consider the totality of the dose distribution to evaluate the dosimetric quality of a low-dose-rate prostate implant. TCP is not a monotonic function of extreme or moderate underdosing. In some instances, extreme underdosing of relatively small volumes may result in a greater TCP than moderate underdosing of relatively large volumes and vice versa.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2004
Proton and hyperpolarized helium magnetic resonance imaging of radiation-induced lung injury in rats.
To assess the usefulness of hyperpolarized helium (3He) MRI, including apparent diffusion coefficient measurements, in the detection and evaluation of radiation-induced lung injury in rats. ⋯ This is the first study to show that hyperpolarized 3He MRI can detect radiation-induced lung injury noninvasively. Reduced hyperpolarized 3He ADC values postradiation likely reflect reduced alveolar volumes associated with fibrosis of the interstitium. Future studies at earlier time points may determine whether this noninvasive imaging technique can detect lung damage before clinical symptoms. Development of this new approach of magnetic resonance lung imaging in the rat model of radiation-induced lung injury will increase the ability to develop appropriate algorithms and more accurate models of the normal tissue complication probability.