Relationship between PSA kinetics and Tc-99m HYNIC PSMA SPECT/CT detection rates of biochemical recurrence in patients with prostate cancer after radical prostatectomy.

Abstract

Prostate-specific antigen (PSA) levels should reflect or be proportional to the size and the metabolic activity of prostatic metastases. Moreover, a rapid change in PSA kinetics, either before or after treatment, is an indicator of poor prognosis after radical prostatectomy. Therefore, the purpose of this study was to investigate the effect of total PSA at the time of Tc-99m HYNIC PSMA SPECT/CT (trigger PSA), PSA velocity (PSAvel), and PSA doubling time (PSAdt) on the Tc-99m HYNIC PSMA SPECT/CT detection rate in prostate cancer patients who showed biochemical recurrence after radical prostatectomy during follow-up. In total, 208 patients who showed an increase in PSA were evaluable for this retrospective analysis covering November 2015 to March 2017. Data were available for calculation of PSAvel in 112 patients and for PSAdt in 157 patients. Logistic regression analysis was used to determine whether there was a relationship between the PSA levels and PSA kinetics and the rate of detection of relapse using Tc-99m HYNIC PSMA SPECT/CT. Tc-99m HYNIC PSMA SPECT/CT detected disease relapse in 151 of 208 patients (72.6%). The PSA level (P < 0.0001) and PSAdt (P = 0.0036) were significantly different between SPECT-positive patients (higher PSA level, shorter PSAdt) and SPECT-negative patients (lower PSA, longer PSAdt). ROC analysis showed that a PSA level of 1.30 ng/mL and a PSAdt of 2.9 months were optimal cut-off values. Patients with purely local recurrence had lower PSAvel and longer PSAdt values (P < 0.001). According to the multivariate analysis, a pathological positive SPECT/CT scan was associated with the PSA level (P < 0.001), PSAdt <6 months (P < 0.05), and Gleason scores (GSC) >7 (P < 0.05). The Tc-99m HYNIC PSMA SPECT/CT detection rate is influenced by trigger PSA, PSAdt, and PSAvel. Like PSA, PSAdt is an independent predictor of Tc-99m HYNIC PSMA SPECT/CT. PSAdt should be taken into account by physicians especially when PSA <1 ng/mL.