Does post-neuromodulation APF signal interstitial cystitis treatment success?

Baltimore-Interstitial cystitis biomarkers didn't change with long-term neuromodulation in a study presented at the AUA annual meeting in Anaheim, CA. Those results were a surprise because a previous short-term study from the University of Maryland, Baltimore, where the marker was discovered, found significant changes after receiving implants.

Researchers from William Beaumont Hospital in Royal Oak, MI, used neuromodulation to treat 11 patients with documented, refractory IC. Patients completed voiding diaries, symptom score questionnaires, and global response assessments and had urine collected for analysis at baseline, at 2 weeks after neuromodulation began, and at 1, 3, and 6 months follow-up. Investigators measured levels of APF, heparin-binding growth factor-like growth factor (HB-EGF), and epidermal growth factor (EGF).

Mean voided volume rose from about 86 mL at baseline to 159 mL at the end of the test phase, dropping somewhat to 103 mL at 6 months. Urgency scores on a 0-to-10 scale dropped significantly from a mean of about 6 to about 3 by the 1-month mark, rising to 4 at 6 months.

At baseline, 10 of 11 patients (91%) had APF activity characteristic of IC, as demonstrated in previous studies, but those levels did not change significantly during follow-up. HB-EGF levels also did not change significantly; however, EGF levels rose transiently, with a statistically significant difference (p<.007) at the 2-week mark, after which they resumed a level similar to that seen at baseline throughout the rest of the study.

Studies differ substantively

In the University of Maryland study (Urology 2000; 55:643-6), six patients underwent 5 days of continuous sacral neuromodulation with leads placed percutaneously at S3. For those patients, all parameters improved significantly, and urinary frequency became normal: Mean frequency dropped from about 23 episodes per day to 4. Mean pelvic pain scores went from 7 to 2, and mean urgency scores fell from 6 to 2. Mean levels of HB-EGF jumped sevenfold from 1.5 ng/mL to 11.0 ng/mL, and urinary APF activity decreased from –76.1% to –4.5%.

Although the William Beaumont Hospital investigators did not compare levels of the markers in IC patients with those of healthy controls at baseline, the IC patients' levels in this study were consistent with levels in IC patients from previous studies.

"It would still lead us to believe that [APF activity] can be a good urine marker for IC," said presenter Richard C. Bennett, MD, a resident physician at William Beaumont working with Kenneth Peters, MD.