title: Dosimetric parameters that predict late rectal complications after curative radiotherapy in patients with uterine cervical carcinoma.
abstract: 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.
authors.affiliation: Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi, Korea.
authors.forename: Tae
authors.initials: T
authors.lastname: Hyun Kim
authors.forename: Jinho
authors.initials: J
authors.lastname: Choi
authors.forename: Sung-Yong
authors.initials: SY
authors.lastname: Park
authors.forename: Seok-Ho
authors.initials: SH
authors.lastname: Lee
authors.forename: Kyu-Chan
authors.initials: KC
authors.lastname: Lee
authors.forename: Dae Sik
authors.initials: DS
authors.lastname: Yang
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Shin
authors.forename: Kwan Ho
authors.initials: KH
authors.lastname: Cho
authors.forename: Hyun-Sun
authors.initials: HS
authors.lastname: Lim
authors.forename: Joo-Young
authors.initials: JY
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011874:Radiometry; D011878:Radiotherapy / Q000009:adverse effects; D012007:Rectum / Q000528:radiation effects*; D012189:Retrospective Studies; D015996:Survival Rate; D002583:Uterine Cervical Neoplasms / Q000401:mortality / Q000532:radiotherapy*