TY - JOUR
T1 - Prostate position late in the course of external beam therapy
T2 - Patterns and predictors
AU - Zellars, Richard C.
AU - Roberson, Peter L.
AU - Strawderman, Myla
AU - Zhang, Daowen
AU - Sandler, Howard M.
AU - Ten Haken, Randall K.
AU - Osher, David
AU - McLaughlin, P. William
PY - 2000/6/1
Y1 - 2000/6/1
N2 - Purpose: To examine prostate and seminal vesicles position late in the course of radiation therapy and to determine the effect and predictive value of the bladder and rectum on prostate and seminal vesicles positioning. Methods and Materials: Twenty-four patients with localized prostate cancer underwent a computerized tomography scan (CT1) before the start of radiation therapy. After 4-5 weeks of radiation therapy, a second CT scan (CT2) was obtained. All patients were scanned in the supine treatment position with instructions to maintain a full bladder. The prostate, seminal vesicles, bladder, and rectum were contoured. CT2 was aligned via fixed bony anatomy to CT1. The geometrical center and volume of each structure were obtained and directly compared. Results: The prostate shifted along a diagonal axis extending from an anterior-superior position to a posterior-inferior position. The dominant shift was to a more posterior-inferior position. On average, bladder and rectal volumes decreased to 51% (±29%) and 82% (±45%) of their pretreatment values, respectively. Multiple regression analysis (MRA) revealed that bladder movement and volume change and upper rectum movement were independently associated with prostate motion (p = 0.016, p = 0.003, and p = 0.052 respectively). Conclusion: Patients are often instructed to maintain a full bladder during a course of external beam radiation therapy, in the hopes of decreasing bladder and small bowel toxicity. However, our study shows that large bladder volumes late in therapy are strongly associated with posterior prostate displacement. This prostate displacement may result in marginal miss. (C) 2000 Elsevier Science Inc.
AB - Purpose: To examine prostate and seminal vesicles position late in the course of radiation therapy and to determine the effect and predictive value of the bladder and rectum on prostate and seminal vesicles positioning. Methods and Materials: Twenty-four patients with localized prostate cancer underwent a computerized tomography scan (CT1) before the start of radiation therapy. After 4-5 weeks of radiation therapy, a second CT scan (CT2) was obtained. All patients were scanned in the supine treatment position with instructions to maintain a full bladder. The prostate, seminal vesicles, bladder, and rectum were contoured. CT2 was aligned via fixed bony anatomy to CT1. The geometrical center and volume of each structure were obtained and directly compared. Results: The prostate shifted along a diagonal axis extending from an anterior-superior position to a posterior-inferior position. The dominant shift was to a more posterior-inferior position. On average, bladder and rectal volumes decreased to 51% (±29%) and 82% (±45%) of their pretreatment values, respectively. Multiple regression analysis (MRA) revealed that bladder movement and volume change and upper rectum movement were independently associated with prostate motion (p = 0.016, p = 0.003, and p = 0.052 respectively). Conclusion: Patients are often instructed to maintain a full bladder during a course of external beam radiation therapy, in the hopes of decreasing bladder and small bowel toxicity. However, our study shows that large bladder volumes late in therapy are strongly associated with posterior prostate displacement. This prostate displacement may result in marginal miss. (C) 2000 Elsevier Science Inc.
KW - Prostate
KW - Prostate motion
KW - Prostatic neoplasms
KW - Radiotherapy
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U2 - 10.1016/S0360-3016(00)00469-7
DO - 10.1016/S0360-3016(00)00469-7
M3 - Article
C2 - 10837948
AN - SCOPUS:0034213169
SN - 0360-3016
VL - 47
SP - 655
EP - 660
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
IS - 3
ER -