Biological-effective versus conventional dose volume histograms correlated with late genitourinary and gastrointestinal toxicity after external beam radiotherapy for prostate cancer: a matched pair analysis.
BACKGROUND
To determine whether the dose-volume histograms (DVH's) for the rectum and bladder constructed using biological-effective dose (BED-DVH's) better correlate with late gastrointestinal (GI) and genitourinary (GU) toxicity after treatment with external beam radiotherapy for prostate cancer than conventional DVH's (C-DVH's).


METHODS
The charts of 190 patients treated with external beam radiotherapy with a minimum follow-up of 2 years were reviewed. Six patients (3.2%) were found to have RTOG grade 3 GI toxicity, and similarly 6 patients (3.2%) were found to have RTOG grade 3 GU toxicity. Average late C-DVH's and BED-DVH's of the bladder and rectum were computed for these patients as well as for matched-pair control patients. For each matched pair the following measures of normalized difference in the DVH's were computed: (a) deltaAUC = (Area Under Curve [AUC] in grade 3 patient--AUC in grade 0 patient)/(AUC in grade 0 patient) and (b) deltaV60 = (Percent volume receiving = 60 Gy [V60] in grade 3 patient--V60 in grade 0 patient)/(V60 in grade 0 patient).


RESULTS
As expected, the grade 3 curve is to the right of and above the grade 0 curve for all four sets of average DVH's--suggesting that both the C-DVH and the BED-DVH can be used for predicting late toxicity. deltaAUC was higher for the BED-DVH's than for the C-DVH's--0.27 vs 0.23 (p = 0.036) for the rectum and 0.24 vs 0.20 (p = 0.065) for the bladder. deltaV60 was also higher for the BED-DVH's than for the C-DVH's--2.73 vs 1.49 for the rectum (p = 0.021) and 1.64 vs 0.71 (p = 0.021) for the bladder.


CONCLUSIONS
When considering well-established dosimetric endpoints used in evaluating treatment plans, BED-DVH's for the rectum and bladder correlate better with late toxicity than C-DVH's and should be considered when attempting to minimize late GI and GU toxicity after external beam radiotherapy for prostate cancer.
Department of Radiation and Cellular Oncology, University of Chicago Hospitals, Chicago, USA. jani_1969@yahoo.com
Ashesh B
AB
Jani
Christopher M
CM
Hand
Charles A
CA
Pelizzari
John C
JC
Roeske
Lani
L
Krauz
Srinivasan
S
Vijayakumar
D000368:Aged; D016022:Case-Control Studies; D004307:Dose-Response Relationship, Radiation; D005767:Gastrointestinal Diseases / Q000209:etiology*; D006801:Humans; D008297:Male; D052801:Male Urogenital Diseases / Q000209:etiology*; D008954:Models, Biological; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000528:radiation effects*; D001743:Urinary Bladder / Q000528:radiation effects*