PSMA-PET shows diagnostic accuracy in initial staging of prostate cancer

Findings from a recent study show that prostate-specific membrane antigen (PSMA)-PET may have diagnostic value in the initial staging of patients with intermediate- and high-risk prostate cancer.¹

The diagnostic accuracy of PSMA-PET in detecting pelvic lymph node involvement was 80.9%.

In total, the study included 122 patients with intermediate- and high-risk prostate cancer who were staged with ⁶⁸Ga-PSMA-11 PET/CT. Participants underwent either radical prostatectomy (n = 36) or radical prostatectomy plus pelvic lymph node dissection (n = 86). The median time between imaging and radical prostatectomy was 20 days, and the median time between imaging and biopsy was 34 days.

Overall, PSMA-PET was able to visualize the primary tumor in 96.7% of patients.

Nodal involvement was detected in 28.1% of patients (25 of 89) who underwent pelvic lymph node dissection. The diagnostic accuracy of PSMA-PET in detecting pelvic lymph node involvement was 80.9%. The sensitivity and specificity of PSMA-PET for pelvic lymph node involvement was 75% and 82.2%, respectively.

The diagnostic accuracy of PSMA-PET in detecting extracapsular extension was 68%, and 89.3% in detecting seminal vesicle infiltration. Overall, PSMA-PET detected extracapsular extension in 15 patients (7 true positives, 8 false positives), and seminal vesical infiltration in 26 patients (15 true positives, 11 false positives).

The investigators also found a positive correlation between prostate specific antigen (PSA) levels and SUV_max, suggesting that elevated PSA levels were linked with increased uptake of the PSMA tracer (Spearman's r: 0.303; P < .001). Significantly higher SUV_max values were observed among patients with a PSA level greater than 20 ng/mL, a Gleason score of 7b or higher, an ISUP grade above 2, and extracapsular extension.

Specifically, patients with a PSA level greater than 20 ng/mL demonstrated a median SUV_max of 15.3, compared with 8.9 among those with a PSA less than 20 ng/mL. There was a weak positive correlation between these values (Spearman’s r = 0.303; P < .001). Similarly, those with a Gleason score of 7b or higher and an ISUP grade greater than 2 demonstrated a median SUV_max of 11.6, compared with 8.8 among those with a Gleason score of 7a or lower and an ISUP grade of 2 or lower (P = .034).

There were no differences in SUV_max when patients were stratified by intermediate or high-risk or other histopathological variables.

“The SUV_max values were significantly greater in patients with criteria of high risk,” the authors noted. “This suggests that semiquantitative parameters, such as SUV_max, could play an important role in the evaluation of tumor aggressiveness in a pre-surgical setting.”

Despite these findings, they also cautioned, “The limitations of our study include its retrospective nature, the lack of comparison with other imaging methods, the exclusion of patients with metastatic disease, and the evaluation of the findings based on patients and not individual lesions.”

Reference

1. Rosales JJ, Antar VB, Mínguez F, et al. Comparison of staging using [⁶⁸Ga]Ga-PSMA-11 PET/CT and histopathological results in intermediate- and high-risk prostate cancer patients treated with radical prostatectomy and pelvic lymph node dissection. Rev Esp Med Nucl Imagen Mol (Engl Ed). 2024:500076. doi:10.1016/j.remnie.2024.500076