OBJECTIVES:
* Compare the accuracy of radiotherapy delivery using multiple CT scans to guide patient positioning vs the standard portal image guided procedure in patients with prostate cancer undergoing external beam radiotherapy.
* Determine the reduction in the proportion of patients with large target positioning errors using the CT-guided procedure.
* Determine organ motion and setup errors over the course of radiotherapy in order to develop efficient clinical intervention strategies in these patients.
OUTLINE: Patients undergo radiotherapy over 9 weeks. Patients undergo a CT scan immediately prior to receiving radiotherapy on treatment days 3-8 and then weekly thereafter. On 3 different days, patients also undergo CT scan immediately after radiotherapy. If the CT scans indicate a correction that exceeds the action level currently in effect, then beginning with the next treatment, the patient's position with respect to the radiation field is adjusted.
PROJECTED ACCRUAL: A total of 25 patients will be accrued for this study within 2 years.
