Researchers have reported promising results using fluorescence microscopy and a photodynamic agent to detect shed prostate cancer (PCa) cells in voided urine, according to a recent report.

Their results show that the technique—which involves treating voided urine specimens with the photodynamic agent 5-aminolevulinic acid (5-ALA) following by imaging with fluorescence microscopy (PPIX)—has a greater sensitivity for detecting PCa than digital rectal examination (DRE) and transrectal ultrasound and a greater specificity than PSA and PSA density, the investigators noted.

“To our knowledge, this is the first successful demonstration of PPIX in urine sediments treated with 5-ALA used to detect PCa in a noninvasive yet highly sensitive manner,” the authors wrote in an online report in BMC Urology. “However, further studies are warranted to determine the role of PPIX-PPD for PCa detection.”

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Yashushi Nakai, MD, and colleagues at Nara Medical University in Nara, Japan, tested the approach in 138 men with an abnormal DRE and/or elevated PSA levels. Needle prostate biopsies revealed PCa in 81 (58.7%). Of these 81 patients, 60 were PPIX-positive, for a sensitivity of 74.1%. Although 57 patients did not have PCa by conventional diagnostic procedures, 17 of these at-risk patients were PPIX-positive, for a specificity of 70.2%.

Dr. Nakai’s group noted that the positivity rate of their approach did not increase with increasing total PSA or tumor stage, but did increase with increasing Gleason score, although the trend was not statistically significant. “These results showed a possibility that PCa detection with PPIX-PPD [photodynamic diagnosis] identified more clinically significant PCa compared with PCa detected by other reported methods.”

The authors stated that although their findings were “quite compelling,” the study had limitations. For example, they obtained limited pathologic data on the patients with positive PPIX-PDD results and positive prostate biopsy results who proceeded to undergo radical prostatectomy. In addition, with a limited follow-up (mean 27 months), they noted that the false-positive PPIX-PDD results must be interpreted cautiously.