Abstract
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Objectives: Prostate-specific membrane antigen (PSMA) is overexpressed on almost all types of prostate cancer cells, making it an ideal target for the diagnosis and treatment of prostate cancer. Both of radionuclide 68Ga and 18F labeled PSMA PET imaging has high sensitivity and specificity to prostate cancer[1-3]. PSMA PET may be a useful tool to identify and define malignant lesions prior to prostate biopsy[1,3,4]. The previous study has shown that the latter provides better image quality and ability to display small lesions[5]. The purpose of our study was to explore the feasibility and accuracy of prebiopsy 18F-DCFPyL PET/CT or PET/MRI and ultrasound (PET/CT-US or PET/MRI-US) fusion guided prostate biopsy for intraprostatic PET positive lesion.
Methods: A total of 55 (mean age = 67, range = 49-84 years) patients with isolated concentrated radioactive (PET positive) lesions on prostate 18F-DCFPyL PET/CT or PET/MRI (Biograph mMR, Siemens Healthcare, Erlangen, Germany) were included to undertake PET/CT-US or PET/MRI-US fusion targeted prostate biopsy. The biopsy was performed with the bk Predictive Fusion prostate biopsy system (Bikai medical technology (Shanghai) co., LTD). First, the 18F-DCFPyL PET/CT or PET/MRI images were imported into the bk Predictive Fusion prostate biopsy system and an SUVmax value of 2.5 was used to delineate the boundary of PET positive lesions. The SUVmax, SUVmean and volume of lesions were also recorded. Then the delineated lesions were fused with transrectal ultrasound images acquired during prostate biopsy. 1-4 needle biopsies were performed at each PET positive lesion, a typical case was shown in figure 1 (The white area (short arrow) is the boundary of the prostate, the pink area (long arrow) is targeted biopsy area, and the long white line represented the puncture needle which reached the target biopsy area). The biopsy pathological findings were used as the gold standard for diagnosis, and the lesions with Gleason scores≥7 were considered as clinically significant prostate cancer.
Results: Among all the 55 patients 41 patients received PET/CT and 23 patients received PET/MRI. 9 patients underwent both PET/CT and PET/MR sequentially. The average volume of the target biopsy area was 3.68 ± 2.18 cm3 (0.7cm3-9.82cm3), the average SUVmax was 15.47 ± 12.25 (4.36-59.34), and the average SUVmean was 7.07 ± 4.68 (3.39-30.30). According to histopathology, fusion targeted biopsy identified 51 of 55 (94.4%) patients as prostate cancer. A total of 178 needle biopsies were performed and 146 samples were malignant resulting an accuracy of 82.0%. Among the 51 prostate cancer patients, 47 (92.2%) cases were clinically significant prostate cancer (13 cases of Gleason scores= 3+4,16 cases of Gleason scores= 4 + 3,10 cases of Gleason scores= 4 +4, 1 case of Gleason scores= 5 + 3, 7 cases of Gleason scores= 4+5), and 4 cases were of no clinical significance (Gleason scores=3+3). 9 patients underwent 18F-DCFPyL PET/CT and PET/MRI successively. 7 of the patients showed abnormal MR signal (short T2 signal, high DWI signal, decreased ADC value) at the site of PET positive lesions, a typical case was shown in figure 2, and the subsequently pathologically confirmed prostate cancer. The other 2 patients showed normal MR signal at the sites of PET positive lesions, a typical case was shown in figure 3, and the subsequent biopsy confirmed prostatic hyperplasia and prostatitis.
Conclusions: 18F-DCFPyL PET/CT-US or PET/MRI-US guided prostate biopsy can detect prostate cancer with a very high positive rate (94.4%). In addition, PET/MR may reduce the number of unnecessary prostate biopsies in some patients with PET positive and MRI negative lesions, and it is expected to further improve the prostate biopsy efficiency. But for patients with pacemakers or claustrophobia, 18F-DCFPyL PET/CT-US guided prostate biopsy remains a relatively ideal option.