Plasma ghrelin O‐acyltransferase (GOAT) enzyme levels show promise as a potential noninvasive biomarker for the detection of significant prostate cancer in individuals at risk for the disease, according to the results of a recent study published in the Journal of Cellular and Molecular Medicine (2018 Sept 6. Epub ahead of print).

Citing widespread criticism of the “overdiagnosis” of prostate cancer primarily as a result of prostate-specific antigen (PSA)-based screening, Raúl M. Luque, PhD, Associate Professor of Cell Biology, Department of Cell Biology, Physiology and Immunology, University of Córdoba, Spain, and colleagues asserted that there is a vital need for novel diagnostic and prognostic biomarkers of prostate cancer—especially significant prostate cancer—and sought to explore the potential of using plasma GOAT levels in this setting.

“[A]dditional accessible biomarkers should be implemented in daily clinical practice, especially those with a prognostic and predictive value of Sig PCa [significant prostate cancer] at the point of screening, which is the current greatest unmet clinical need, as this may reduce unnecessary interventions,” they said.

Plasma GOAT Levels Versus PSA Levels

The study by Dr Luque and colleagues included 3 cohorts (N = 312)—healthy individuals without suspected prostate cancer and a PSA <2.5 ng/mL (n = 65), patients with negative biopsy results who are at risk for prostate cancer (n = 64), and patients with positive biopsy results who are at risk for prostate cancer (n = 183).

Dr Luque and colleagues collected blood samples from all participants to determine and compare the levels of GOAT and PSA in their plasma. Plasma GOAT levels were evaluated with an ELISA kit, and in 2 cohorts (healthy controls versus patients with prostate cancer); significant prostate cancer was defined by a Gleason Score of 7 or higher. DeLong tests were used over the respective areas under the curves (AUC) to assess and compare performance. The performance of multivariate models based on these measures was then investigated, after the addition of complementary clinical variables.

Unveiling A New Biomarker for Prostate Cancer

Patients with prostate cancer had significantly higher plasma PSA levels than their healthy counterparts (6.35 ng/mL vs 0.69 ng/mL, respectively; P <.05). Plasma levels of GOAT were significantly higher among patients with prostate cancer and a positive biopsy than in those with a negative biopsy and with healthy patients. Although plasma GOAT and PSA levels were significantly elevated in patients with significant prostate cancer compared with patients with nonsignificant prostate cancer, these differences were statistically more significant for GOAT versus PSA levels (P = .002 vs P = .0145, respectively).

In addition, GOAT levels were associated with diagnoses of significant prostate cancer and were independent of traditional clinical variables (eg, PSA, age, and digital rectal exam). With regard to significant prostate cancer diagnosis, GOAT levels outperformed PSA levels in patients with PSA levels ranging from 3 ng/mL to 20 ng/mL (GOAT‐AUC = 0.612 vs PSA‐AUC = 0.494).

“Our results show, for the first time, that the measurement of plasma GOAT levels might represent a significantly better diagnostic marker than plasma PSA levels, exhibiting higher AUC, particularly on those individuals with PSA levels ranging 3‐10 ng/mL (the PSA grey‐zone) or 3‐20 ng/mL,” Dr Luque and colleagues concluded.—Janelle Bradley