Bacterial Urinary Tract Infection after Transrectal Placement of Fiducial Markers prior to Proton Radiotherapy for Prostate Cancer

PURPOSE: To determine the incidence of a bacterial urinary tract infection (UTI) necessitating hospitalization after transrectal placement of fiducial markers prior to proton radiotherapy (RT) for prostate cancer. MATERIALS AND METHODS: Six hundred sixty six patients returning for follow up after proton RT consented to participate in this institutional review board (IRB) approved study. Patients were queried whether they required hospitalization within 1 month of transrectal placement of fiducial markers. Patients were treated with proton RT between August 2006 and December 2014. Median International Prostate Symptom Score (IPSS) was 7. Sixty four patients (9.6%) had diabetes, 9 patients (1.4%) had chronic obstructive pulmonary disease, 6 patients (0.9%) had prior bladder surgery, 7 patients (1.1%) had a transurethral prostatectomy within 3 months, and 549 patients (82.4%) had a course of antibiotics within 6 months. Fifty five patients (8.3%) were taking tamsulosin, 16 patients (2.4%) were taking finasteride, and 62 patients (9.3%) were taking saw palmetto. The interval between the most recent prostate biopsy prior to fiducial placement and fiducial marker placement was less than 6 months in 609 patients (91.4%). No patient had a prior recent rectal culture. RESULTS: Ten patients (1.5%) developed a bacterial UTI necessitating hospitalization after transrectal placement of fiducial markers. A bacterial UTI occurred in 3 (0.7%) of 440 patients treated from 2006 to 2012 and in 7 (3.1%) of 226 patients treated from 2013 to 2014. Univariate analysis of potential association of a bacterial UTI with the following parameters revealed: IPSS less than or greater than the median (p=0.3400), diabetes (p=0.6099), tamsulosin (p=0.9999), saw palmetto (p=0.0093), interval between prostate biopsy and placement of fiducials (p=0.9999), year of treatment (p=0.0363), and antibiotics within 6 months (p=0.2233). A bacterial UTI was observed in 4 (6.5%) of 62 patients who were taking saw palmetto versus 6 (1.0%) of 604 patients who were not taking this medication. The incidence of a bacterial UTI between 2006 and 2012 was 3 (0.7%) of 440 patients and from 2013 to 2014 was 7 (3.1%) of 226 patients. Multivariate analysis revealed that the likelihood of a bacterial UTI was increased in patients taking saw palmetto (p=0.0044) and those treated in 2013-2014 (p=0.0303). CONCLUSION: The incidence of a bacterial UTI requiring hospitalization after transrectal placement of fiducial markers prior to proton RT was 1.5% and was impacted by taking saw palmetto and year of treatment. Patients treated during 2013 and 2014 had a significantly higher risk of a bacterial UTI requiring hospitalization.