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Background/Aim: To identify predictors of adverse gastrointestinal (GI) events related to stereotactic body radiation therapy (SBRT) for liver tumors. Patients and Methods: We retrospectively analyzed 56 patients who underwent SBRT for liver tumors at our institution between 2016 and 2021. The a/ß ratio of the GI tract (stomach, duodenum, and large intestine) was assumed to be 3 Gy in the Linear-Quadratic model (LQ model). The dose to the GI tract, that is, the biologically effective dose 3 (BED3) was converted to a 2 Gy equivalent dose (Gy2/3=2 Gy equivalent dose, a/ß=3). Using this 2 Gy equivalent dose, predictors of adverse GI events of Grade 2 or higher were investigated. Results: The median observation period was 10 months (0-40 months) and median age was 77 years (range=29-93 years). Forty-three of the 56 patients had hepatocellular carcinoma and the other 13 had metastatic liver tumors. Tumors were irradiated with 30-54 Gy/5-18 fractions of planning target volume D95% prescription (80% isodose). Eight of the 56 patients had Grade 2 or higher adverse GI events. By univariate analysis, GI D1cc, Dmax, V20, V25, V30, and V35 were all significant predictors of Grade 2 or higher adverse GI events. Among these, gastrointestinal V35 was the most significant predictor of Grade 2 or higher adverse GI events. Conclusion: For SBRT of liver tumors, GI V35 was the best predictor of Grade 2 or higher adverse GI events. [ABSTRACT FROM AUTHOR]

Background Hypofractionated radiotherapy using fewer and larger fractional doses may be more beneficial than conventional external-beam radiotherapy for localized prostate cancer. We evaluated the 5-year outcomes of moderately hypofractionated radiotherapy for localized prostate cancer. Methods We retrospectively evaluated 195 patients with localized prostate cancer (T1-3N0M0) who underwent intensity-modulated radiotherapy (IMRT) (66 Gy delivered in fractions of 3 Gy every other weekday) between May 2005 and December 2011. Patients received androgen deprivation therapy depending on the perceived intermediate or high risk of their disease. A prostate-specific antigen nadir +2.0 ng/ ml indicated biochemical failure. We assessed toxicity using the Radiation Therapy Oncology Group and the European Organization for Research and Treatment of Cancer (RTOG/ EORTC) criteria, and patient-reported outcomes using the Expanded Prostate Cancer Index Composite (EPIC). Results The risk classifications (proportion) were low risk (13.8%), intermediate risk (35.9%), and high risk (50.3%). The median follow-up was 69 months. Thirteen (6.66%) patients experienced biochemical failure within a median of 40 months (interquartile range, 25-72 months). The 5-year overall survival rate and no biological evidence of disease rate were 97.7% and 92.4%, respectively. Based on the RTOG/EORTC criteria, no patient experienced acute or late toxicity of grade 3 or higher. The EPIC scores revealed significant differences in the average value of all domains (p < 0.01). At 1 month postradiotherapy completion, the general urinary and bowel domain scores had decreased, but these scores returned to baseline level by 3 months post radiotherapy. Conclusions The moderately hypofractionated radiotherapy protocol yielded short-term satisfactory clinical outcomes with acceptable toxicity. [ABSTRACT FROM AUTHOR]