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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Dosimetric parameters that predict late rectal complications after curative radiotherapy in patients with uterine cervical carcinoma.Hyun Kim T, Choi J, Park SY, Lee SH, Lee KC, Yang DS, Shin KH, Cho KH, Lim HS, Kim JY Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi, Korea. BACKGROUND: Late rectal complication (LRC) was a major late complication in patients with uterine cervical carcinoma who were treated with a combination of external beam radiotherapy (EBRT) and high-dose-rate intracavitary irradiation (HDR-ICR). For the current study, the authors retrospectively evaluated dosimetric parameters that were correlated with LRC > or = Grade 2 in patients with uterine cervical carcinoma who were treated with curative radiotherapy, and they analyzed the appropriate dose estimates to the rectum that were predictive for LRC > or = Grade 2. METHODS: Between July 1994 and September 2002, 157 patients who were diagnosed with Stage IB-IIIB cervical carcinoma and were treated with definitive radiotherapy were included. EBRT (41.4-66 grays [Gy] in 23-33 fractions) to the whole pelvis was delivered to all patients, with midline shielding performed after a 36-50.4 Gy external dose. HDR-ICR (21-39 Gy in 6-13 fractions to Point A) was administered at a rate of 2 fractions weekly after midline shielding of EBRT. LRC was scored using Radiation Therapy Oncology Group criteria. The total biologically effective dose (BED) at specific points, such as Point A (BED(Point A)), rectal point (BED(RP)), and maximal rectal point (BED(MP)), was determined by a summation of the EBRT and HDR-ICR components, in which the alpha/beta ratio was set to 3. Analyzed parameters included patient age, tumor size, stage, concurrent chemotherapy, ICR fraction size, RP ratio (dose at the rectal point according to the Point A dose), MP ratio (dose at the maximal rectal point according to the Point A dose), EBRT dose, BED(Point A), BED(RP), and BED(MP). RESULTS: The 5-year actuarial overall rate of LRC > or = Grade 2 in all patients was 18.4%. Univariate analysis showed that the RP ratio, MP ratio, EBRT dose, BED(Point A), BED(RP), and BED(MP) were correlated with LRC > or = Grade 2 (P < 0.05). Multivariate analysis showed that, of all clinical and dosimetric parameters evaluated, only BED(RP) was correlated with LRC > or = Grade 2 (P = 0.009). The 5-year actuarial rate of LRC > or = Grade 2 was 5.4% in patients with a BED(RP) < 125 Gy(3) and 36.1% in patients with a BED(RP) > or = 125 Gy(3) (P < 0.001). CONCLUSIONS: BED(RP) was a useful dosimetric parameter for predicting the risk of LRC > or = Grade 2 and should be limited to < 125 Gy(3) whenever possible to minimize the risk of LRC > or = Grade 2 in patients with uterine cervical carcinoma who are treated with a combination of EBRT and HDR-ICR. Cancer 2005. Published 6 September 2005 in Cancer, 104(6): 1304-11.
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