Question explored with the scientific record
Conversation so far
- 1 Can psma pet scans show false positives
- 2 Which benign conditions most commonly cause PSMA PET uptake?
- 3 Can bph show up as prostate cancer on bi parametric MRIs and PMSA pet scans
- 4 But what if circulating psa is low ie. 3.5 for 77 year old male
Answered on this page ↓
But what if circulating psa is low ie. 3.5 for 77 year old male
PSMA PET can detect prostate cancer even when PSA is low, but false positives from other PSMA-avid tissues are a real concern.
The evidence shows PSMA PET detects prostate cancer at PSA levels well below 3.5 ng/mL. One meta-analysis found positive PET rates of 66% for PSA 1.0-1.99 ng/mL and 91% for PSA 0.2-0.99 ng/mL [4]. A 2021 study found PSMA-PET frequently detected recurrence in patients with rising PSA below the Phoenix threshold (PSA nadir + 2 ng/mL), well within your range [2]. The tracer binds prostate-specific membrane antigen overexpressed in cancer cells [8, 9].
But PSMA is not exclusive to prostate cancer. A 2016 case report documented a PSMA-avid pancreatic neuroendocrine tumor in a 75-year-old man with a very low PSA of 0.36 µg/L [1]. A 2018 report found a primary lung adenocarcinoma positive on PSMA PET in a patient with rising PSA after prostatectomy [5]. PSMA expression also occurs in thyroid tumor vasculature [3]. These are documented false-positive sources.
The retrieved studies did not include a systematic review of false-positive rates across all non-prostatic tissues, so the overall frequency is not clear from this evidence. One 2018 comparison study included 36 patients and found PSMA PET detected lesions in 75% of patients with recurrent prostate cancer, versus 53% for choline PET [6]. Another small feasibility study showed that inflammatory lung lesions can also take up PSMA [7].
My call: PSMA PET can yield true-positive findings at PSA 3.5 in a 77-year-old man, but false positives from other PSMA-avid tissues (lung, pancreas, thyroid, inflammation) are a real possibility. The PSA level alone does not rule out a false positive. Confidence: moderate, limited by the absence of a large systematic review of false-positive rates from this retrieval.
Sources used 9
-
Prostate-Specific Membrane Antigen (PSMA) Avid Pancreatic Neuroendocrine Tumor
This study presents a case of a 75-year-old man with a history of prostate cancer who was found to have a PSMA-avid pancreatic neuroendocrine tumor, highlighting the potential for false-positive PSMA uptake in imaging.
DOI: 10.1097/RLU.0000000000001308 -
Detection of Recurrent Prostate Cancer Using Prostate-specific Membrane Antigen Positron Emission Tomography in Patients not Meeting the Phoenix Criteria for Biochemical Recurrence After Curative Radiotherapy
PSMA-PET frequently detected prostate cancer recurrence in patients with rising PSA below the Phoenix threshold after curative radiotherapy, calling into question whether this threshold remains adequate in the PSMA-PET era.
DOI: 10.1016/j.euo.2020.01.002 -
PSMA expression by microvasculature of thyroid tumors – Potential implications for PSMA theranostics
Endothelial PSMA expression in thyroid tumor vasculature is common but highly heterogeneous across tumor types, being more prevalent in RAIR/high-grade cancers and suggesting PSMA-targeted imaging/therapy potential with important pitfalls from non-thyroid PSMA expression and den…
DOI: 10.1038/s41598-017-05481-z -
Sensitivity, Specificity, and Predictors of Positive 68 Ga–Prostate-specific Membrane Antigen Positron Emission Tomography in Advanced Prostate Cancer: A Systematic Review and Meta-analysis
This systematic review and meta-analysis evaluates the diagnostic performance of 68 Ga-PSMA PET imaging in detecting metastatic prostate cancer, highlighting its sensitivity and specificity in relation to pre-PET PSA levels.
DOI: 10.1016/j.eururo.2016.06.021 -
Primary Lung Adenocarcinoma With 68Gallium Prostate-Specific Membrane Antigen-PET/CT Scan Avidity in a Patient on Surveillance After Prostatectomy
This case report discusses a 76-year-old patient with prostate cancer who, after prostatectomy and rising PSA levels, was found to have a primary lung adenocarcinoma detected via PSMA PET/CT scan, highlighting the importance of differentiating between prostatic lung metastases a…
DOI: 10.1016/j.clgc.2018.03.009 -
68Ga-PSMA and 11C-Choline comparison using a tri-modality PET/CT-MRI (3.0 T) system with a dedicated shuttle
Prospective intrasubject comparison of 68Ga-PSMA PET/CT versus 11C-Choline PET/CT for detecting recurrent prostate cancer using a tri-modality PET/CT-MRI (3.0 T) system with a dedicated shuttle, showing higher lesion detection and tumor-to-background ratios for PSMA and demonstr…
DOI: 10.1186/s41824-018-0027-1 -
Enhancing PSMA-uptake with androgen deprivation therapy – a new way to detect prostate cancer metastases?
A small feasibility study in five men with biochemical recurrence of prostate cancer tested whether a single low-dose androgen deprivation therapy (degarelix) could increase PSMA uptake on 68Ga-PSMA PET/CT and thus improve detection of metastases; two patients showed increased u…
DOI: 10.1590/S1677-5538.IBJU.2018.0305 -
Prostate-specific membrane antigen expression is greatest in prostate adenocarcinoma and lymph node metastases
This study investigates the expression of prostate-specific membrane antigen (PSMA) in prostate adenocarcinoma and lymph node metastases, finding that PSMA is expressed in all benign and malignant prostatic tissues, with the highest expression in primary cancer.
DOI: 10.1016/S0090-4295(98)00278-7 -
Prostate‐specific membrane antigen (PSMA) protein expression in normal and neoplastic tissues and its sensitivity and specificity in prostate adenocarcinoma: an immunohistochemical study using mutiple tumour tissue microarray technique
This study investigates the expression of prostate-specific membrane antigen (PSMA) in normal and neoplastic tissues, demonstrating its sensitivity and specificity in diagnosing prostate adenocarcinoma (PaC) using a multiple tumour tissue microarray technique.
DOI: 10.1111/j.1365-2559.2007.02635.x