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In Patients Experiencing Biochemical Failure After Radiotherapy, Pretreatment Risk Group and PSA Velocity Predict Differences in Overall Survival and Biochemical Failure-Free Interval
Page 1295
D. E. Soto, R. R. Andridge, C. C. Pan, S. G. Williams, J. M. G. Taylor, and H. M. Sandler
These authors studied a group of patients with localized prostate cancer who had biochemical recurrence after definitive radiotherapy. A notable percentage of these patients had favorable pretreatment risk group features and pretreatment PSA velocities, confirming that patients with such favourable characteristics can occasionally have PSA-defined recurrence. Despite biochemical recurrence, however, these patients had superior survival outcomes compared with patients with recurrence who had unfavorable risk group features or pretreatment PSA velocities. This emphasizes the challenges of using PSA failure alone as a surrogate for a survival endpoint.
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Effect of High-Dose-Rate 192Ir Source Activity on Late Rectal Bleeding After Intracavitary Radiation Therapy for Uterine Cervix CancerPage 1329
O. Suzuki, Y. Yoshioka, F. Isohashi, M. Morimoto, T. Kotsuma, Y. Kawaguchi, K. Konishi, S. Nakamura, H. Shiomi, and T. Inoue
The dose rate effect in low-dose-rate brachytherapy has been well described. By contrast, this effect has not been studied in the setting of high-dose-rate brachytherapy (HDR-BT). This study examined the incidence of late rectal bleeding after HDR-BT for uterine cervical cancer in terms of the dose rate (source activity) of the HDR Ir-192 source. The incidence of late rectal bleeding was high in the high rectal biologic effective dose group, and the higher source activity was associated with a significantly higher incidence of rectal bleeding (58% vs. 27%, p < 0.05). This appears to be the first report of the dose rate effect in HDR-BT.
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Impact of Drug Therapy, Radiation Dose, and Dose Rate on Renal Toxicity Following Bone Marrow TransplantationPage 1436
J. C. Cheng, T. E. Schultheiss, and J. Y. C. Wong
This study used multivariate logistic regression to analyze combined data from published reports of renal injury following total body irradiation. The salient findings were a dose response for adults, a dose-rate effect below but not above 10 cGy/min, and a significant nephrotoxic effect from fludarabine. However, there was no evidence of increased radiation sensitivity in the pediatric population compared with adults. In the pediatric population, nephrotoxicity appears to mainly be due to the drug therapies associated with hematopoietic stem cell transplants rather than the radiation dose.
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Underestimation of Low-Dose Radiation in Treatment Planning of Intensity-Modulated RadiotherapyPage 1537
S. Y. Jang, H. H. Liu, and R. Mohan
The authors performed a dosimetric study to understand the degree of dose accuracy, particularly in low-dose regions of intensity-modulated radiation therapy (IMRT). Comparison of Monte Carlo simulations and conventional dose calculations in available commercial treatment planning systems revealed that the low doses in IMRT plans are likely underestimated if the secondary radiation from the multi-leaf collimators used in IMRT is not modeled adequately. The authors recommend that clinical facilities be aware of this potential low-dose error and account for its effect appropriately in IMRT treatment planning.
