Intensity-modulated radiotherapy reduces gastrointestinal toxicity in patients treated with androgen deprivation therapy for prostate cancer.
OBJECTIVE
Androgen deprivation therapy (AD) has been shown to increase late Grade 2 or greater rectal toxicity when used concurrently with three-dimensional conformal radiotherapy (3D-CRT). Intensity-modulated radiotherapy (IMRT) has the potential to reduce toxicity by limiting the radiation dose received by the bowel and bladder. The present study compared the genitourinary and gastrointestinal (GI) toxicity in men treated with 3D-CRT+AD vs. IMRT+AD.


METHODS
Between July 1992 and July 2004, 293 men underwent 3D-CRT (n = 170) or IMRT (n = 123) with concurrent AD (<6 months, n = 123; ≥6 months, n = 170). The median radiation dose was 76 Gy for 3D-CRT (International Commission on Radiation Units and Measurements) and 76 Gy for IMRT (95% to the planning target volume). Toxicity was assessed by a patient symptom questionnaire that was completed at each visit and recorded using a Fox Chase Modified Late Effects Normal Tissue Task radiation morbidity scale.


RESULTS
The mean follow-up was 86 months (standard deviation, 29.3) for the 3D-CRT group and 40 months (standard deviation, 9.7) for the IMRT group. Acute GI toxicity (odds ratio, 4; 95% confidence interval, 1.6-11.7; p = .005) was significantly greater with 3D-CRT than with IMRT and was independent of the AD duration (i.e., <6 vs. ≥6 months). The interval to the development of late GI toxicity was significantly longer in the IMRT group. The 5-year Kaplan-Meier estimate for Grade 2 or greater GI toxicity was 20% for 3D-CRT and 8% for IMRT (p = .01). On multivariate analysis, Grade 2 or greater late GI toxicity (hazard ratio, 2.1; 95% confidence interval, 1.1-4.3; p = .04) was more prevalent in the 3D-CRT patients.


CONCLUSIONS
Compared with 3D-CRT, IMRT significantly decreased the acute and late GI toxicity in patients treated with AD.
Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Navesh K
NK
Sharma
Tianyu
T
Li
David Y
DY
Chen
Alan
A
Pollack
Eric M
EM
Horwitz
Mark K
MK
Buyyounouski
D000368:Aged; D000369:Aged, 80 and over; D000726:Androgen Antagonists / Q000627:therapeutic use; D003131:Combined Modality Therapy / Q000009:adverse effects / Q000379:methods; D016001:Confidence Intervals; D005500:Follow-Up Studies; D041981:Gastrointestinal Tract / Q000528:radiation effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009367:Neoplasm Staging; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000473:pathology / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D014566:Urogenital System / Q000528:radiation effects
D000726:Androgen Antagonists