Clinical toxicities and dosimetric parameters after whole-pelvis versus prostate-only intensity-modulated radiation therapy for prostate cancer.
OBJECTIVE
To assess whether whole-pelvis (WP) intensity-modulated radiation therapy (IMRT) is associated with increased toxicity compared with prostate-only (PO) IMRT.


METHODS
We retrospectively analyzed all patients with prostate cancer undergoing definitive IMRT to 79.2 Gy with concurrent androgen deprivation at our institution from November 2005 to May 2007 with a minimum follow-up of 12 months. Thirty patients received initial WP IMRT to 45 Gy in 1.8-Gy fractions, and thirty patients received PO IMRT. Study patients underwent computed tomography simulation and treatment planning by use of predefined dose constraints. Bladder and rectal dose-volume histograms, maximum genitourinary (GU) and gastrointestinal (GI) Radiation Therapy Oncology Group toxicity grade, and late Grade 2 or greater toxicity-free survival curves were compared between the two groups by use of the Student t test, Fisher exact test, and Kaplan-Meier curve, respectively.


RESULTS
Bladder minimum dose, mean dose, median dose, volume receiving 5 Gy, volume receiving 20 Gy, volume receiving 40 Gy, and volume receiving 45 Gy and rectal minimum dose, median dose, and volume receiving 20 Gy were significantly increased in the WP group (all p values < 0.01). Maximum acute GI toxicity was limited to Grade 2 and was significantly increased in the WP group at 50% vs. 13% the PO group (p = 0.006). With a median follow-up of 24 months (range, 12-35 months), there was no difference in late GI toxicity (p = 0.884) or in acute or late GU toxicity.


CONCLUSIONS
Despite dosimetric differences in the volume of bowel, bladder, and rectum irradiated in the low-dose and median-dose regions, WP IMRT results only in a clinically significant increase in acute GI toxicity, in comparison to PO IMRT, with no difference in GU or late GI toxicity.
Deville
Curtiland
C
Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA 19104, USA. deville@uphs.upenn.edu
Both
Stefan
S
Hwang
Wei-Ting
WT
Tochner
Zelig
Z
Vapiwala
Neha
N
D000368:Aged; D000726:Androgen Antagonists / Q000627:therapeutic use; D018572:Disease-Free Survival; D041981:Gastrointestinal Tract / Q000528:radiation effects*; D006801:Humans; D015182:Lymphatic Irradiation / Q000009:adverse effects* / Q000379:methods; D008297:Male; D010388:Pelvis; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000473:pathology*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods; D012007:Rectum / Q000528:radiation effects; D012189:Retrospective Studies; D012306:Risk; D047368:Tumor Burden; D001743:Urinary Bladder / Q000528:radiation effects; D014566:Urogenital System / Q000528:radiation effects*
D000726:Androgen Antagonists