The role of (Ga)PSMA I&T in biochemical recurrence after radical prostatectomy: detection rate and the correlation between the level of PSA, Gleason score, and the SUV.

Objective: The aim of the study was to retrospectively evaluate the recurrence detection rate of Gallium-68-prostate-specific membrane antigen [(Ga)PSMA] imaging and therapy (I&T) positron emission tomography/computed tomography (PET/CT) at different PSA levels, which enables early detection of patients with radical prostatectomy. We also aimed to compare Gleason scores, used drugs (LHRH analogs and antiandrogens), PSA levels with SUV values, and detection rates.

Method: This retrospective study included 107 patients who underwent radical prostatectomy and who underwent (Ga)PSMA I&T PET/CT imaging between January 2015 and December 2018 for the early detection of recurrence. The PSA values, Gleason scores, treatments, lesions detected on (Ga)PSMA I&T, and SUV values were recorded for all patients.

Results: Patients with a median PSA level of 1.22 ng/mL were divided into seven groups according to the PSA values. The lowest lesion detection rate was found to be 7/16 patients (43.8%) when the PSA was < 0.2 ng/ml, and the highest lesion detection rate was found to be 33/33 patients (100%) when the PSA was > 3.5 ng/ml. There was a positive correlation between PSA level and ppSUV (per patient SUV) value of the patients with lesions (p < 0.001 and r = 0.49). As the Gleason score increased, the lesion detection rates also increased and there was a significant correlation between these values (p < 0.001 and r = 0.360). A positive correlation was determined between the Gleason scores and ppSUV values in patients with lesions (p = 0.007 and r = 0.302). A statistically significant correlation was found between bicalutamide use and lesion detection on (Ga)PSMA I&T (p < 0.001). A similar relationship was also determined in patients undergoing maximal androgen blockade (MAB) (p = 0.003). Patients determined with lesions on (Ga)PSMA I&T and who were administered luteinizing hormone-releasing hormone (LHRH) agonists were found to have statistically significantly higher ppSUV values than those who were not administered LHRH agonists (p < 0.001). In binary logistic regression test, when PSA levels and Gleason scores were selected as continuous variables, both PSA levels and Gleason scores were demonstrated as significant covariates (p = 0.006 and p = 0.022) for lesion detection; by contrast, bicalutamide and MAB were not found as significant factors.

Conclusion: In the present study, (Ga)PSMA I&T was found to be quite successful in determining lesions in the biochemical recurrence, which is consistent with the findings of other I&T studies and studies conducted with different PSMA ligands. Thus, it can be considered that the use of (Ga)PSMA I&T will become increasingly common.