The value and significance of routine urine cultures in patients referred for radiation therapy of prostatic malignancy.

Radiation therapy of the prostate requires a simulator visit when a urinary catheter and rectal balloon are used for field determination. Radiation changes combined with the previous instrumentation, surgery and therapy makes diagnosing urinary tract infection (UTI) difficult. For this study a UTI was defined as the isolation of the same organism(s) at any concentration in two of three sequential urine samples. Urine cultures were obtained prior to radiation therapy (during and after the simulator visit) and while receiving radiation treatments. The study of 291 patients revealed a UTI in 20 (6.9%) prior to undergoing simulator evaluation and in an additional 13 patients at the first visit after to give an incidence of 11.34% prior to receiving radiation. The bacterial isolates in the 13 patients were more suggestive of reactivated chronic infection than catheter associated UTI. During radiation therapy approximately 1%-2% of patients developed a UTI per week. This study justified the use of routine urine cultures in these patients and suggests that further investigations should be done to reduce the incidence of infections occurring both prior to and during radiation therapy.