Table 1.

Summary of strengths of conventional imaging (PCWG2/3) and advantages and limitations of PSMA PET/CT.

Advantages of conventional imaging (PCWG2/3)	Advantages of PSMA PET/CT	Limitations of PSMA PET/CT
• CT, MRI and bone scan are widely available • Decades of experience in reporting and standardization (such as RECIST criteria for CT and PCWG criteria for progression on bone scan) despite limitations • Funded by healthcare providers in most countries	• Detection rate in prostate or prostatectomy bed comparable or higher than MRI • Detection of nodal metastasis not limited by size criteria • Higher detection rate for metastatic disease particularly in lower PSA range • Lower false-positive rate (nodal, osseous and visceral) • High negative predictive value for enlarged but not metastatic nodes • Nodal, osseous and visceral metastases measurable separately by volume which can be used for monitoring therapy response • Detection of primary or local recurrence, nodal, osseous and visceral disease on a single-imaging modality ‘one-stop shop’ with higher degree of confidence than conventional imaging • Detection of marrow disease before visible on bone scan or CT • Direct visualization of tumour rather than its secondary effect (osteoblastic activity or sclerosis), closing the lag time between (a) PSA progression and a positive scan and (b) PSA response and resolution of lesions on imaging	• Lesions (including prostatic, nodal or visceral) smaller than 4 mm could potentially be below PET resolution • No standardized criteria for reporting are widely recognized including measurement of total disease burden (nodal, osseous or visceral) • Possible ‘PSMA upregulation’ immediately following initiation of ADT or novel antiandrogens in mCRPC; timing and significance of these changes are not yet well defined • May not be ideal as a single modality in very advanced disease as PSMA expression may be lost; complementary role of FDG PET/CT is needed • Not yet funded by healthcare providers; cost is highly variable by jurisdictions (but not necessarily higher than conventional imaging) • Several similar but slightly different radiopharmaceuticals currently in use; results likely comparable

ADT, androgen-deprivation therapy; CT, computed tomography; FDG, fluorodeoxyglucose; mCRPC, metastatic castration-resistant prostate cancer; MRI, magnetic resonance imaging; PCWG2/3, Prostate Cancer Working Group 2/3; PET, positron-emission tomography; PSA, prostate-specific antigen; PSMA, prostate-specific-membrane antigen.