The role of (⁶⁸Ga)PSMA I&T in biochemical recurrence after radical prostatectomy: detection rate and the correlation between the level of PSA, Gleason score, and the SUV_max

The aim of the study was to retrospectively evaluate the recurrence detection rate of Gallium-68-prostate-specific membrane antigen [(⁶⁸Ga)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_max values, and detection rates.

This retrospective study included 107 patients who underwent radical prostatectomy and who underwent (⁶⁸Ga)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 (⁶⁸Ga)PSMA I&T, and SUV_max values were recorded for all patients.

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_max (per patient SUV_max) 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_max 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 (⁶⁸Ga)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 (⁶⁸Ga)PSMA I&T and who were administered luteinizing hormone-releasing hormone (LHRH) agonists were found to have statistically significantly higher ppSUV_max 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.

In the present study, (⁶⁸Ga)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 (⁶⁸Ga)PSMA I&T will become increasingly common.