Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan.
To determine the predictive risk factors for Grade 2 or worse rectal bleeding after high-dose-rate brachytherapy (HDR-BT) combined with hypofractionated external-beam radiotherapy (EBRT) for prostate cancer using dose-volume histogram analysis.
The records of 216 patients treated with HDR-BT combined with EBRT were analyzed. The treatment protocols for HDR-BT were 5 Gy × five times in 3 days or 7 Gy × three, 10.5 Gy × two, or 9 Gy × two in 2 days. The EBRT doses ranged from 45 to 51 Gy with a fractional dose of 3 Gy.
In 20 patients Grade 2 or worse rectal bleeding developed, and the cumulative incidence rate was 9% at 5 years. By converting the HDR-BT and EBRT radiation doses into biologic effective doses (BED), the BED(3) at rectal volumes of 5% and 10% in the patients who experienced bleeding were significantly higher than those in the remaining 196 patients. Univariate analysis showed that a higher rectal BED(3-5%) and the use of fewer needles in brachytherapy were correlated with the incidence of bleeding, but BED(3-5%) was found to be the only significant factor on multivariate analysis.
The radiation dose delivered to small rectal lesions as 5% is important for predicting Grade 2 or worse rectal bleeding after HDR-BT combined with EBRT for prostate cancer.
Okamoto M, Ishikawa H, Ebara T, Kato H, Tamaki T, Akimoto T, Ito K, Miyakubo M, Yamamoto T, Suzuki K, Takahashi T, Nakano T. Are you the author?
Reference: Int J Radiat Oncol Biol Phys. 2011 May 26. Epub ahead of print.