Percutaneous transgluteal Ga-68 PSMA PET/CT guided prostate biopsy: Is it the future?

Introduction: Prostatic cancer is the most common non-cutaneous malignancy in men and the second leading cause of cancer-related mortality. A trans-rectal ultra-sonographic guided biopsy from the prostate is done to establish a pathological diagnosis in patients with abnormal digital rectal examination or increased serum PSA levels having a sensitivity of 39-52% even after rebiopsy. Moreover, a higher number of cores is associated with higher morbidity. Ga-68 PSMA-PET/CT has documented role in staging and follow-up evaluation of prostate cancer. The study was planned to evaluate the PSMA-PET/CT-guided biopsy from a PSMA-expressing prostatic lesion through the trans-gluteal approach to avoid the rectal penetration.

Methods: In the present study, we prospectively recruited patients with clinical suspicion of prostate cancer (serum PSA >4ng/dl), either biopsy-naïve or negative TRUS-guided biopsy. All the patients underwent whole-body Ga-68 PSMA-PET/CT-imaging. Two qualified nuclear medicine physicians reviewed PET/CT imaging. A focal PSMA avid lesion in the prostate was considered PET-positive. No or inhomogenous PSMA expression was considered as PET negative. The PET-positive patients underwent PET-guided prostatic biopsies through the trans-gluteal approach using an automated-robotic arm to place the needle to target prostatic lesions. Society of interventional radiology consensus guidelines was followed for the procedures. The location of tracer uptake in the prostate, SUVmax, miPSMA score, visual analysis score (VAS) for pain, procedure-related complication, and histopathology were documented. Urine culture reports at 48 hours after the procedure was also evaluated.

Results: A total of 96 patients (biopsy-naïve 52; TRUS-GB 44) were enrolled. In these patients, the mean PSA level was 18.0 ±13.3 (range 4.3-59.7) ng/dl). Of these, 72/96 (75%) patients were PET-positive with mean SUV max 19.1 ±13.9. Of them, 43 were biopsy-naïve, and 29 had negative TRUS guided biopsy. The lesions were located anteriorly in 20, posteriorly in 12, laterally in 30 and central in 8 patients. All the PET-positive patients underwent PET/CT-guided prostatic biopsy. Biopsy was technically feasible in 70/72 procedures, and retrieved specimens were adequate for pathological analysis. Two patients had a non-representative sample and a repeat biopsy was done, which demonstrated representative specimen. Histopathology demonstrated prostate cancer in 70 patients and chronic prostatitis in the remaining two patients. The procedure demonstrated a diagnostic yield of 100%. In the TRUS-GB group, 29/44 patients had prostate cancer and 8/29 (27%) had clinically significant prostate cancer (Gleason score ≥ 7). Minor complications (hematuria, hematospermia and gluteal pains) were noted in ten patients. Non of the patient required hospital admission. The mean VAS was 2.5 ±1.8 (> 5 in six). A statistically significant correlation was noted between SUVmax and miPSMA score (rho= 0.765; P<0.0001), PSA and miPSMA-score (0.484; P=0.0004), as well as PSA and SUVmax of the lesion (rho= 0.475; P=0.0006). The intensity of pain was not related to the depth of the lesion (rho= -0.129; P=0.37). None of the patients developed fever or post-procedural infection.

Conclusions: The present study demonstrated that transgluteal PSMA PET/CT-guided prostatic biopsy is feasible, safe, and has excellent diagnostic yield. This approach is highly practical in patients with prior negative TRUS-guided biopsies. It also negates the chance of inoculation of the prostate with rectal flora, thus reducing the morbidity due to bacterial infection. The findings pave the way for use of PSMA-PET/CT and guided prostate biopsy for early diagnosis of prostate cancer. Moreover, the potential risk of Covid-19 cross-infection with TRUS-GB due to fecal contamination can be avoided by this approach.