Prospective evaluation of the effect of ionizing radiation on the bladder tumor-associated (BTA) urine test

Abstract

Purpose: To prospectively evaluate the effect of ionizing radiation on the results of the bladder tumor-associated antigen (BTA) test. By examining this question, we sought to determine its potential use as a monitoring test for the detection of recurrent transitional carcinoma of the bladder in patients who have received prior radiotherapy for bladder preservation. Materials and Methods: Between February 1996 and April 1997, 18 patients with nonbladder pelvic malignancies and no history of bladder cancer, received irradiation to the bladder. These patients were prospectively evaluated using the BTA test at the end of the external-beam radiation (EBRT) and at 3-month follow-up intervals. Urine cytology was analyzed in 16 of the 18 patients at the end of EBRT. A median of 3 separate measurements were made (range 1–6) on each patient. The median dose of EBRT was 50.4 Gy (range 30–68Gy). Seven patients underwent brachytherapy as part of their treatment course. BTA results and time intervals were recorded and analyzed using univariate and Kaplan–Meyer methodologies. Results: A total of 10 (56%) of the 18 patients had a positive BTA test at some time following completion of EBRT. Of the 10 positive tests, 9 returned to negative in a median of 42 weeks from completion of EBRT. Treatment with chemotherapy, brachytherapy, calculated bladder dose, and total external beam dose did not significantly influence either the number of positive tests or the time to resolution of the positive test in this small group of patients. All screened urine samples were negative for malignant cells and 11 (69%) of 16 showed changes consistent with ionizing radiation. Conclusion: Our findings support the hypothesis that ionizing radiation can cause transient positive results in the BTA test, but that these normalize with time. Although it requires further testing, it seems that the BTA test may be useful in the detection of recurrence in patients with bladder cancer who have been treated with definitive irradiation for bladder preservation.