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Incorporating 68Ga‑PSMA PET/CT imaging findings with clinical information improves detection of clinically significant prostate cancer in men with elevated PSA in the “grey zone” of 4-10 ng/mL, investigators report. Another research team suggests that some men aged 80 years and older with high PSA levels can avoid prostate biopsy altogether based on 68Ga‑PSMA PET/CT results. A third set of researchers examined the false-positive rate of PSMA PET to assess whether it can reliably replace prostate biopsy.
Reducing Overdiagnosis
In a study of 81 men (mean age 64 years) with total PSA levels of 4-10 ng/mL, 29 men had clinically significant prostate cancer based on transrectal ultrasound/magnetic resonance imaging (MRI)/PET fusion-guided biopsy and 52 did not. The clinically significant prostate cancer group had smaller prostate volumes (median 31.40 mL), lower free to total PSA ratios (median, 0.12), higher PSA densities (median 0.21 ng/mL2), and higher PI-RADS scores (PI-RADS 3-5 in 86.21% vs 55.8%) compared with the group with nonsignificant cancer.
A prediction model incorporating 68Ga-PSMA PET/CT maximal standardized uptake value, prostate volume, and free to total PSA ratio demonstrated the highest area under the curve (AUC, 0.927) for detecting prostate cancer, Shuo Hu, PhD, of Xiangya Hospital, Central South University, Changsha in Hunan, China, and colleagues reported in Cancer Imaging. The diagnostic sensitivity and specificity of the prediction model were 86.21% and 86.54%, respectively.
PSA alone, multiparametric MRI alone, and 68Ga-PSMA PET/CT alone had AUCs of 0.585, 0.652, and 0.850, respectively.
“This combined analysis has important clinical significance for reducing unnecessary prostate biopsies because of the improvement in specificity,” Dr Hu and colleagues wrote.
Avoiding Unnecessary Biopsy
In a separate study published in the Journal of Nuclear Medicine, investigators examined 100 consecutive patients aged 80 years and older who were referred for PSMA PET/CT with or without a preimaging biopsy. The median PSA level was 22.6 ng/mL, with 53% and 13% of patients having a PSA level above 20 and 100 ng/mL, respectively.
According to 68Ga-PSMA-11 PET/CT results, 36, 25, and 39 patients had localized, locally advanced, and advanced disease, respectively – indicating that all 100 patients had prostate cancer, Einat Even-Sapir, MD, PhD, of Tel Aviv Sourasky Medical Center and Tel Aviv University in Israel, and colleagues reported.
Of the 100 patients, 34 were referred for 68Ga-PSMA-11 PET/CT on clinical suspicion only and did not undergo biopsy. They were more frequently older (median age 87 vs. 82 years), with poor performance status scores (Eastern Cooperative Oncology Group performance status 2 or higher in 23.5% vs 1.5%), and had higher median PSA (57 vs 15.4 ng/mL) compared with the biopsied group.
“It seems that PSMA PET/CT is highly likely to identify and stage PCa in patients at least 80 y old with a PSA level of at least 20 ng/mL, even without histopathologic confirmation,” Dr Even-Sapir’s team wrote.
The investigators proposed a treatment algorithm for patients at least 80 years old who have high PSA or urinary symptoms or bone pain and undergo PSMA PET/CT. Men suspected to have advanced disease probably will not need biopsy. Men with localized or locally-advanced disease suitable for aggressive therapies should consider biopsy.
In this cohort, most patients with advanced disease on imaging received hormonal therapy whether or not they underwent biopsy. Biopsy-naïve men with localized/locally-advanced disease, however, were less likely than biopsied men to receive definitive therapies. The radiation therapy rate, for example, was 2.9% vs 53.0%, respectively.
“Advanced disease identified on PSMA PET/CT can be considered confirmatory of PCa and serve as a criterion to initiate hormonal therapy, potentially waiving the need for preimaging biopsy in frail patients,” the investigators concluded.
Biopsy-Free Radical Prostatectomy?
“For PSMA-PET, the expression of prostate-specific membrane antigen (PSMA) in benign prostatic hyperplasia (BPH) tissue and its related positive reaction, which can reduce the specificity of diagnosis, are the crucial concerns affecting the imaging diagnosis of PCa as well as the feasibility of biopsy-free [radical prostatectomy],”Yi Cai, MD, of Xiangya Hospital, Central South University, in Changsha City, China, and colleagues wrote in The Journal of Urology.
In their retrospective study of 89 men with benign prostatic hyperplasia, the investigators found that the false positive rate of PSMA-PET in detecting prostate cancer was 30%. Using the maximum standardized uptake value (SUVmax) excluded men with benign prostatic hyperplasia and grade group 1 cancer with an AUC of 0.86, they reported. An optimal SUVmax cutoff value of 15 had 100% specificity but 41% sensitivity. By comparison, using both PET score and mpMRI PI-RADS criteria of 4-5 in diagnosing clinically significant prostate cancer among 94 men yielded 100% specificity with 49% sensitivity.
“Currently, biopsy-free RP is still in its infant stage and its application must be approached with great caution,” according to Dr Cai’s team.
References
Yang J, Li J, Xiao L, et al. 68Ga-PSMA PET/CT-based multivariate model for highly accurate and noninvasive diagnosis of clinically significant prostate cancer in the PSA gray zone. Cancer Imaging. 2023;23(1):81. doi:10.1186/s40644-023-00562-x
Kesler M, Cohen D, Levine C, et al. Staging prostate cancer with 68Ga-PSMA-11 PET/CT in the elderly: Is preimaging biopsy imperative? J Nucl Med. 2023;64(7):1030-1035. doi:10.2967/jnumed.122.265371
Tang W, Tang Y, Qi L, et al. BPH-related false positive of PSMA-PET in the diagnosis of prostate cancer: the Achilles’ heel of biopsy-free radical prostatectomy? J Urol. Published online August 30, 2023. doi:10.1097/JU.0000000000003680
This article originally appeared on Renal and Urology News
