Radiotherapy Research Today is a free monthly online journal that collates and summarizes the latest research about Radiotherapy, including details on cancer treatment, side effects. | ||||||||
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Effect of high-dose-rate 192Ir source activity on late rectal bleeding after intracavitary radiation therapy for uterine cervix cancer.Suzuki O, Yoshioka Y, Isohashi F, Morimoto M, Kotsuma T, Kawaguchi Y, Konishi K, Nakamura S, Shiomi H, Inoue T Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari, Osaka, Japan. suzuki-os@mc.pref.osaka.jp PURPOSE: This retrospective study analyzed the effect of the activity of high-dose-rate (HDR) (192)Ir source on late rectal bleeding after HDR intracavitary radiotherapy (ICRT) in patients with uterine cervix cancer. METHODS AND MATERIALS: One hundred thirty-two patients who underwent HDR-ICRT and external beam radiotherapy (EBRT) were analyzed. The rectal point dose in ICRT was calculated by inserting a lead wire into the rectal lumen and summed with the whole-pelvic EBRT dose. The rectal biologic effective dose (BED) was calculated. The relationship between averaged source activity or the BED and late rectal bleeding were analyzed. RESULTS: Three-year actuarial rectal bleeding probabilities were 46% (> or =100 Gy(3)) and 18% (< or = 100 Gy(3)), respectively (p < 0.005). When patients were divided into four groups according to rectal BED (> or = or < or =100 Gy(3)) and source activity (> or = or < or =2.4 cGy.m(2).h(-1)), the group with both a high BED and high activity showed significantly greater probability (58% at 3 years; p < 0.005). It was noted that the probability of the group with BED of 100 Gy(3) or greater was high, but that was not the case with 2.4 cGy.m(2).h(-1) or less. CONCLUSION: This is the first clinical report concerning the source activity effect of HDR (192)Ir on late rectal bleeding in patients undergoing HDR-ICRT. This suggests that when source activity is higher than 2.4 cGy.m(2).h(-1), ICRT should be performed with more caution not to exceed 100 Gy(3) in total. Published 21 July 2008 in Int J Radiat Oncol Biol Phys, 71(5): 1329-34.
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