Rectal dose-volume constraints in high-dose radiotherapy of localized prostate cancer.
OBJECTIVE
To investigate the relationship between rectal bleeding and dosimetric-clinical parameters in patients receiving three-dimensional conformal radiotherapy (3D-CRT) for localized prostate cancer.


METHODS
In a retrospective national study (AIROPROS01-01, AIRO: Associazione Italiana Radioterapia Oncologica), planning/clinical data for 245 consecutive patients with stage T1-4N0-x prostate carcinoma who underwent 3D-CRT to 70-78 Gy (ICRU point) were pooled from four Italian institutions. The correlation between late rectal bleeding and rectal dose-volume data (the percentage of rectum receiving more than 50, 55, 60, 65, 70, and 75 Gy [V(50-70)]) and other dosimetric and clinical parameters were investigated in univariate (log-rank) and multivariate (Cox regression model) analyses. Median follow-up was 2 years.


RESULTS
Twenty-three patients were scored as late bleeders according to a modified RTOG definition (Grade 2: 16; Grade 3: 7); the actuarial 2-year rate was 9.2%. Excepting V75, all median and third quartile V(50-70) values were found to be significantly correlated with late bleeding at univariate analysis. The smallest p value was seen for V(50) below/above the third quartile value (66%). The V70 (cut-off value: 30%) was found to be also predictive for late bleeding. In the high-dose subgroup (74-78 Gy), Grade 3 bleeding was highly correlated with this constraint. The predictive value of both V(50) and V(70) was confirmed by multivariate analyses.


CONCLUSIONS
The present article provides evidence for correlation between rectal DVH parameters and late rectal bleeding in patients treated with curative intent with 3D-CRT. To keep the rate of moderate/severe rectal bleeding below 5-10%, it seems advisable to limit V(50) to 60-65%, V(60) to 45-50%, and V70 to 25-30%.
Fiorino
Claudio
C
Department of Medical Physics and Radiotherapy, H. S. Raffaele, Milano, Italy. fiorino.claudio@hsr.it
Sanguineti
Giuseppe
G
Cozzarini
Cesare
C
Fellin
Gianni
G
Foppiano
Franca
F
Menegotti
Loris
L
Piazzolla
Anna
A
Vavassori
Vittorio
V
Valdagni
Riccardo
R
D000368:Aged; D000704:Analysis of Variance; D005500:Follow-Up Studies; D006471:Gastrointestinal Hemorrhage / Q000209:etiology*; D006801:Humans; D007558:Italy; D008297:Male; D009367:Neoplasm Staging; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000150:complications*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D012002:Rectal Diseases / Q000209:etiology*; D012007:Rectum / Q000528:radiation effects*; D012044:Regression Analysis; D012189:Retrospective Studies