Reduced Recurrence of Low-grade Papillary Bladder Tumors Associated With Asymptomatic Bacteriuria

To determine tumor recurrence rate of low-grade, papillary, and non-muscle-invasive (TaLG) bladder tumors in patients who have asymptomatic bacteriuria (ABU). Microbes in the urine trigger immune responses like intravesical Bacillus Calmette-Guerin, suggesting that common bacteria may also exert an antitumor effect.

We investigated recurrence rates in 387 patients with low-grade, papillary noninvasive bladder tumors TaLG, with or without ABU. They were followed every 6 months for 36 months, and did not receive antibiotics or intravesical chemotherapy. Recurrent tumors were treated generally by outpatient fulguration. Before cystoscopy, patients submitted a voided urine sample for culture, stratified as no growth, <10⁴, >10⁴, or >10⁵ CFU/mL single organism. Any degree of bacteria on culture was classified as ABU. We also measured absolute neutrophil counts (ANC) and the presence of pyuria, as surrogate indicators of local immune response.

Of the 387 cases, 200 (52%) had ABU, including 102 (27%) with >10⁴ CFU/mL bacteriuria. With absolute 3-year follow-up, 75% of patients with ABU survived tumor-free compared to 40% of 187 uninfected patients (P = .001). Sixty percent of patients with negative cultures recurred vs 25%, 14%, and 29% of patients with <10⁴, >10⁴, or >10⁵ CFU/mL. (P = .001). Mean number of recurrent tumors in colonized patients was 4.2 vs 8.4 in uninfected patients (P = .009). ANC averaged 6.3 K/mcL in bacteriuric vs 4.1 K/mcL in uninfected patients (P = .01).

Patients with papillary TaLG tumors and chronic ABU had fewer recurrences, fewer numbers of recurrent tumors, and longer tumor-free survival times than similarly staged uninfected patients. Bladder-resident bacteria may reduce bladder tumor recurrences through local immune mechanisms.