Time point-independent tumor positivity of 68Ga-PSMA-PET/CT pre- and post-biopsy in high-risk prostate cancer

Abstract

Abstract Objective Prostate-specific membrane antigen (PSMA)-PET/CT imaging has gained increasing clinical importance for the detection and staging of high-risk primary prostate cancer (PCa). However, it is unclear whether the routine practice of prostate biopsy obscures the image finding of PSMA-PET/CT. This study aimed to compare the tumor positivity rate of PSMA-PET/CT performed pre- (PSMA-PET/CTpre) and post-biopsy (PSMA-PET/CTpost) in high-risk PCa patients. Patients and methods We matched 58 PSMA-PET/CTpost with 58 PSMA-PET/CTpre studies for primary detection of high-risk PCa according to clinical characteristics. Three subgroups of PSMA-PET/CTpost were defined by the intervals after biopsy (≤ 1 week, 1 ~ 2 weeks, and 2 ~ 5 weeks). Tumor positivity rates were determined, and SUVmax of primary tumors were compared separately for the two main groups and the related subgroups. Malignant prostate tissues from 20 of these patients were examined by immunohistochemical analysis of PSMA. In addition, the values of PSMA-PET/CTpre and PSMA-PET/CTpost in assessing seminal vesicle invasion (SVI) were evaluated in patients who underwent radical prostatectomy. Results All the primary tumors were positive on PSMA-PET/CTpost and PSMA-PET/CTpre imaging, resulting in a patient-based positivity rates of 100% (58/58) in both groups. All examined IHC results (20/20) confirmed the high-level expression of PSMA. SUVmax of primary tumors did not differ between the two main groups (16.1, IQR 9.8–26.6 vs. 16.5, IQR 11.0–26.7, p > 0.05). Subgroup analysis of PSMA-PET/CTpost (≤ 1 week, 1 ~ 2 weeks, and 2 ~ 5 weeks) also showed no significant difference in tumor SUVmax (15.8, IQR 9.5–22.2; 17.8, IQR 9.8–29.2; and 15.4, IQR 10.1–30.3. p > 0.05). PSMA-PET/CTpost and PSMA-PET/CTpre exhibited similar value in SVI detection as well. Conclusions The tumor positivity rate was consistently high for PSMA-PET/CT pre- and post-biopsy. A prior biopsy does not seem to affect the tumor positivity rate of PSMA-PET/CT in high-risk PCa.