Increased risk of biochemical and local failure in patients with distended rectum on the planning CT for prostate cancer radiotherapy.
OBJECTIVE
To retrospectively test the hypothesis that rectal distension on the planning computed tomography (CT) scan is associated with an increased risk of biochemical and local failure among patients irradiated for prostate carcinoma when a daily repositioning technique based on direct prostate-organ localization is not used.


METHODS
This study included 127 patients who received definitive three-dimensional conformal radiotherapy for prostate cancer to a total dose of 78 Gy at The University of Texas M. D. Anderson Cancer Center. Rectal distension was assessed by calculation of the average cross-sectional rectal area (CSA; defined as the rectal volume divided by length) and measuring three rectal diameters on the planning CT. The impact of rectal distension on biochemical control, 2-year prostate biopsy results, and incidence of Grade 2 or greater late rectal bleeding was assessed.


RESULTS
The incidence of biochemical failure was significantly higher among patients with distended rectums (CSA >11.2 cm(2)) on the planning CT scan (p = 0.0009, log-rank test). Multivariate analysis indicates that rectal distension and high-risk disease are independent risk factors for biochemical failure, with hazard ratios of 3.89 (95% C.I. 1.58 to 9.56, p = 0.003) and 2.45 (95% C.I. 1.18 to 5.08, p = 0.016), respectively. The probability of residual tumor without evidence of radiation treatment (as scored by the pathologist) increased significantly with rectal distension (p = 0.010, logistic analysis), and a lower incidence of Grade 2 or greater late rectal bleeding within 2 years was simultaneously observed with higher CSA values (p = 0.031, logistic analysis).


CONCLUSIONS
We found strong evidence that rectal distension on the treatment-planning CT scan decreased the probability of biochemical control, local control, and rectal toxicity in patients who were treated without daily image-guided prostate localization, presumably because of geographic misses. Therefore, an empty rectum is warranted at the time of simulation. These results also emphasize the need for image-guided radiotherapy to improve local control in irradiating prostate cancer.
Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Renaud
R
de Crevoisier
Susan L
SL
Tucker
Lei
L
Dong
Radhe
R
Mohan
Rex
R
Cheung
James D
JD
Cox
Deborah A
DA
Kuban
D000368:Aged; D001706:Biopsy; D004108:Dilatation, Pathologic / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology; D005740:Gases; D006471:Gastrointestinal Hemorrhage / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual / Q000473:pathology; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000150:complications*; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D012007:Rectum / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects; D012189:Retrospective Studies; D013223:Statistics as Topic; D014057:Tomography, X-Ray Computed; D017211:Treatment Failure
D005740:Gases; D017430:Prostate-Specific Antigen