Acute toxicity after image-guided intensity modulated radiation therapy compared to 3D conformal radiation therapy in prostate cancer patients.
OBJECTIVE
Image-guided intensity modulated radiation therapy (IG-IMRT) allows significant dose reductions to organs at risk in prostate cancer patients. However, clinical data identifying the benefits of IG-IMRT in daily practice are scarce. The purpose of this study was to compare dose distributions to organs at risk and acute gastrointestinal (GI) and genitourinary (GU) toxicity levels of patients treated to 78 Gy with either IG-IMRT or 3D-CRT.


METHODS
Patients treated with 3D-CRT (n=215) and IG-IMRT (n=260) receiving 78 Gy in 39 fractions within 2 randomized trials were selected. Dose surface histograms of anorectum, anal canal, and bladder were calculated. Identical toxicity questionnaires were distributed at baseline, prior to fraction 20 and 30 and at 90 days after treatment. Radiation Therapy Oncology Group (RTOG) grade ≥1, ≥2, and ≥3 endpoints were derived directly from questionnaires. Univariate and multivariate binary logistic regression analyses were applied.


RESULTS
The median volumes receiving 5 to 75 Gy were significantly lower (all P<.001) with IG-IMRT for anorectum, anal canal, and bladder. The mean dose to the anorectum was 34.4 Gy versus 47.3 Gy (P<.001), 23.6 Gy versus 44.6 Gy for the anal canal (P<.001), and 33.1 Gy versus 43.2 Gy for the bladder (P<.001). Significantly lower grade ≥2 toxicity was observed for proctitis, stool frequency ≥6/day, and urinary frequency ≥12/day. IG-IMRT resulted in significantly lower overall RTOG grade ≥2 GI toxicity (29% vs 49%, respectively, P=.002) and overall GU grade ≥2 toxicity (38% vs 48%, respectively, P=.009).


CONCLUSIONS
A clinically meaningful reduction in dose to organs at risk and acute toxicity levels was observed in IG-IMRT patients, as a result of improved technique and tighter margins. Therefore reduced late toxicity levels can be expected as well; additional research is needed to quantify such reductions.
Department of Radiation Oncology, Erasmus Medical Center Cancer Institute, Rotterdam, The Netherlands.
Ruud C
RC
Wortel
Department of Radiation Oncology, Erasmus Medical Center Cancer Institute, Rotterdam, The Netherlands.
Luca
L
Incrocci
Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
Floris J
FJ
Pos
Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
Joos V
JV
Lebesque
Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
Marnix G
MG
Witte
Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
Uulke A
UA
van der Heide
Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands.
Marcel
M
van Herk
Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands. Electronic address: w.heemsbergen@nki.nl.
Wilma D
WD
Heemsbergen
D000368:Aged; D001003:Anal Canal / Q000528:radiation effects*; D041981:Gastrointestinal Tract / Q000528:radiation effects; D006801:Humans; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects* / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects* / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods; D012007:Rectum / Q000528:radiation effects*; D001743:Urinary Bladder / Q000528:radiation effects*; D014566:Urogenital System / Q000528:radiation effects