Abstract
To compare an intensity-modulated radiotherapy (IMRT) planning approach for prostate pelvic RT with a conformal RT (CRT) approach taking into account the influence of organ-at-risk (OAR) motion. A total of 20 male patients, each with one planning computed tomography scan and five to eight treatment computed tomography scans, were used for simulation of IMRT and CRT for delivery of a prescribed dose of 50 Gy to the prostate, seminal vesicles, and pelvic lymph nodes. Planning was done in Eclipse without correcting for OAR motion. Evaluation was performed using the CRT and IMRT dose matrices and the planning and treatment OAR outlines. The generalized equivalent uniform dose (gEUD) was calculated for 894 OAR volumes using a volume-effect parameter of 4, 12, and 8 for bowel, rectum and bladder, respectively. For the bowel, the gEUD was normalized to a reference volume of 200 cm(3). For each patient and each OAR, an average of the treatment gEUDs (gEUD(treat)) was calculated for CRT and IMRT. The paired t test was used to compare IMRT with CRT and gEUD(treat) with gEUD(plan). The mean gEUD(treat) was reduced from 43 to 40 Gy, 47 to 46 Gy, and 48 to 45 Gy with IMRT for the bowel, rectum, and bladder, respectively (p < 0.001). Differences between the gEUD(plan) and gEUD(treat) were not significant (p > 0.05) for any OAR but was >6% for the bowel in 6 of 20 patients. Intensity-modulated RT reduced the bowel, rectum, and bladder gEUDs also under influence of OAR motion. Neither CRT nor IMRT was robust against bowel motion, but IMRT was not less robust than CRT.
Highlights
The motivation for introducing intensity-modulated radiotherapy (IMRT) for the treatment of pelvic lymph nodes in prostate cancer patients has been to reduce the incidence of gastrointestinal (GI) adverse effects and, if possible, to escalate the dose to the pelvic lymph nodes
Several planning studies have demonstrated the superiority of IMRT compared with conformal RT (CRT) to shape the dose distribution to the planning target volume (PTV), thereby reducing the dose to the main organs-at-risk (OARs) [1,2,3,4,5,6,7,8,9,10,11,12,13]
In the case of IMRT, Vtreat was significantly greater than Vplan (p = 0.003–0.03) for all intermediate dose levels investigated (i.e., 25–40 Gy); such a difference was found for V25, V45, and V50 for CRT (p = 0.001–0.04)
Summary
The motivation for introducing intensity-modulated radiotherapy (IMRT) for the treatment of pelvic lymph nodes in prostate cancer patients has been to reduce the incidence of gastrointestinal (GI) adverse effects and, if possible, to escalate the dose to the pelvic lymph nodes. Several planning studies have demonstrated the superiority of IMRT compared with conformal RT (CRT) to shape the dose distribution to the planning target volume (PTV), thereby reducing the dose to the main organs-at-risk (OARs) (i.e., the bowel, rectum, and bladder) [1,2,3,4,5,6,7,8,9,10,11,12,13]. In contrast to IMRT, three-dimensional CRT planning is target centric and does not need a planning OAR volume concept [15]. CRT and IMRT dose distributions would show different characteristics in the presence of organ movements
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