Effect of high-dose-rate 192Ir source activity on late rectal bleeding after intracavitary radiation therapy for uterine cervix cancer.
OBJECTIVE
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
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.


CONCLUSIONS
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.
Suzuki
Osamu
O
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
Yoshioka
Yasuo
Y
Isohashi
Fumiaki
F
Morimoto
Masahiro
M
Kotsuma
Tadayuki
T
Kawaguchi
Yoshifumi
Y
Konishi
Koji
K
Nakamura
Satoaki
S
Shiomi
Hiroya
H
Inoue
Takehiro
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects*; D016009:Chi-Square Distribution; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000209:etiology*; D006801:Humans; D007496:Iridium Radioisotopes / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D011832:Radiation Injuries / Q000150:complications*; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects*; D012062:Relative Biological Effectiveness; D012189:Retrospective Studies; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
D007496:Iridium Radioisotopes