Rectal dose and source strength of the high-dose-rate iridium-192 both affect late rectal bleeding after intracavitary radiation therapy for uterine cervical carcinoma.
OBJECTIVE
The purpose of this study was to reconfirm our previous findings that the rectal dose and source strength both affect late rectal bleeding after high-dose-rate intracavitary brachytherapy (HDR-ICBT), by using a rectal dose calculated in accordance with the definitions of the International Commission on Radiation Units and Measurements Report 38 (ICRU(RP)) or of dose-volume histogram (DVH) parameters by the Groupe Européen de Curietherapie of the European Society for Therapeutic Radiology and Oncology.


METHODS
Sixty-two patients who underwent HDR-ICBT and were followed up for 1 year or more were studied. The rectal dose for ICBT was calculated by using the ICRP(RP) based on orthogonal radiographs or the DVH parameters based on computed tomography (CT). The total dose was calculated as the biologically equivalent dose expressed in 2-Gy fractions (EQD(2)). The relationship between averaged source strength or the EQD(2) and late rectal bleeding was then analyzed.


RESULTS
When patients were divided into four groups according to rectal EQD(2) (>or= or <median dose) and source strength (>or= or <2.4 cGy.m(2).h(-1)), the group with both a high EQD(2) and a high source strength showed a significantly greater probability of rectal bleeding for ICRU(RP), D(2cc), and D(1cc). The patients with a median rectal dose above the threshold level did not show a greater frequency of rectal bleeding unless the source strength exceeded 2.4 cGy.m(2).h(-1).


CONCLUSIONS
Our results obtained with data based on ICRU(RP) and CT-based DVH parameters indicate that rectal dose and source strength both affect rectal bleeding after HDR-ICBT.
Isohashi
Fumiaki
F
Department of Radiation Oncology, Osaka University Graduate School of Medicine, Osaka, Japan. isohashi@radonc.med.osaka-u.ac.jp
Yoshioka
Yasuo
Y
Koizumi
Masahiko
M
Suzuki
Osamu
O
Konishi
Koji
K
Sumida
Iori
I
Takahashi
Yutaka
Y
Ogata
Toshiyuki
T
Kotsuma
Tadayuki
T
Inoue
Takehiro
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006471:Gastrointestinal Hemorrhage / Q000209:etiology*; D006801:Humans; D007496:Iridium Radioisotopes / Q000009:adverse effects*; D008875:Middle Aged; D011832:Radiation Injuries / Q000150:complications*; D012002:Rectal Diseases / Q000209:etiology*; D012007:Rectum / Q000528:radiation effects; D012062:Relative Biological Effectiveness; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
D007496:Iridium Radioisotopes