Adaptive image-guided radiotherapy (IGRT) eliminates the risk of biochemical failure caused by the bias of rectal distension in prostate cancer treatment planning: clinical evidence.
OBJECTIVE
Rectal distension has been shown to decrease the probability of biochemical control. Adaptive image-guided radiotherapy (IGRT) corrects for target position and volume variations, reducing the risk of biochemical failure while yielding acceptable rates of gastrointestinal (GI)/genitourinary (GU) toxicities.


METHODS
Between 1998 and 2006, 962 patients were treated with computed tomography (CT)-based offline adaptive IGRT. Patients were stratified into low (n = 400) vs. intermediate/high (n = 562) National Comprehensive Cancer Network (NCCN) risk groups. Target motion was assessed with daily CT during the first week. Electronic portal imaging device (EPID) was used to measure daily setup error. Patient-specific confidence-limited planning target volumes (cl-PTV) were then constructed, reducing the standard PTV and compensating for geometric variation of the target and setup errors. Rectal volume (RV), cross-sectional area (CSA), and rectal volume from the seminal vesicles to the inferior prostate (SVP) were assessed on the planning CT. The impact of these volumetric parameters on 5-year biochemical control (BC) and chronic Grades ≥2 and 3 GU and GI toxicity were examined.


RESULTS
Median follow-up was 5.5 years. Median minimum dose covering cl-PTV was 75.6 Gy. Median values for RV, CSA, and SVP were 82.8 cm(3), 5.6 cm(2), and 53.3 cm(3), respectively. The 5-year BC was 89% for the entire group: 96% for low risk and 83% for intermediate/high risk (p < 0.001). No statistically significant differences in BC were seen with stratification by RV, CSA, and SVP in quartiles. Maximum chronic Grades ≥2 and 3 GI toxicities were 21.2% and 2.9%, respectively. Respective values for GU toxicities were 15.5% and 4.3%. No differences in GI or GU toxicities were noted when patients were stratified by RV.


CONCLUSIONS
Incorporation of adaptive IGRT reduces the risk of geometric miss and results in excellent biochemical control that is independent of rectal volume/distension while maintaining very low rates of chronic GI toxicity.
Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI 48073, USA.
Sean S
SS
Park
Di
D
Yan
Samuel
S
McGrath
Joshua T
JT
Dilworth
Jian
J
Liang
Hong
H
Ye
Daniel J
DJ
Krauss
Alvaro A
AA
Martinez
Larry L
LL
Kestin
D000368:Aged; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D004106:Dilatation; D041981:Gastrointestinal Tract / Q000528:radiation effects; D006801:Humans; D008297:Male; D009929:Organ Size; D058958:Organs at Risk / Q000000981:diagnostic imaging; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects / Q000379:methods*; D012007:Rectum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D012306:Risk; D020379:Risk Adjustment / Q000379:methods; D036542:Tomography, Spiral Computed / Q000379:methods; D014566:Urogenital System / Q000528:radiation effects
D017430:Prostate-Specific Antigen