The role of IGF-1 and the distribution of body fat in decreasing the number of prostate rebiopsies

Abstract

Objective: To assess the usefulness of IGF-1 and internal organ fat measured by bioelectrical impedance audiometry to avoid rebiopsies in patients with persistently high prostate-specific antigen (PSA) levels.

Material and method: A prospective study was conducted with 92 patients who underwent prostate rebiopsy due to high PSA levels with negative results in the rectal examination and a lack of preneoplastic lesions. The patients previously had their IGF-1 levels measured and had undergone an impedance audiometry test using the abdominal Fat Analyser AB-140 TANITA system. We calculated the receiver operating characteristic (ROC) curves for the PSA levels, %PSA, internal organ fat and IGF-1 and PSA density.

Results: Twenty-five patients were diagnosed with prostate cancer. These patients had significantly higher PSA, PSAd and IGF-1 values and a tendency towards higher internal organ fat levels and lower %PSA readings (p=.001, p=.003, p=.001, p=.24 and P=0.28, respectively). The ROC curve showed an area under the curve for IGF-1 and PSA of .82 and .81, respectively. Using the cutoff points for 95% sensitivity and using the 3 criteria as an indication of rebiopsy, 74% of the biopsies would have been spared, leaving undiagnosed only 1 patient with clinically significant cancer -Gleason score>7 (4+3)-. The positive and negative predictive values for the set of variables were higher than for each one separately (PPV: 66/NPV: 63). The cost of both determinations was 82 euros.

Conclusions: Our results suggest that measuring IGF-1 could significantly decrease the number of unnecessary rebiopsies in an inexpensive and safe manner.

Keywords: Cáncer de próstata; Insuline growth factor-1; Obesidad; Obesity; Prostate cancer; Rebiopsia; Rebiopsy.