Nuclear medicine

The researches find that the To compare the accuracy of 68Gallium prostate-specific membrane antigen positron emission tomography/computed tomography; (68Ga-PSMA PET/CT) with mpMRI in detecting and localising primary prostate cancer when compared with radical prostatectomy (RP) pathology. Therefore Retrospective review of men who underwent 68Ga-PSMA PET/CT and mpMRI for primary prostate cancer prior to RP across four centres between 2015 and 2018.

68Ga-PSMA PET/CT

Patients undergoing imaging for recurrent disease or prior to non-surgical treatment were excluded. They defined pathological index tumour as the lesion with highest ISUP Grade Group (GG) on RP. Our primary outcomes were rates of accurate detection and localisation of RP index tumour using 68Ga-PSMA PET/CT or mpMRI. Because They define tumour detection as imaging lesion corresponding with RP tumour on any imaging plane; and localisation as imaging lesion matching RP index tumour in all sagittal; axial and coronal planes.

Secondary outcomes included localisation of clinically significant and transition zone index tumours. They defin clinically significant disease as GG 3-5. They used descriptive statistics and Mann-Whitney U test to define and compare demographic and pathological characteristics between detected; missed and localised tumours using either imaging modality. Therefore They use the McNemar test to compare detection and localisation rates using 68Ga-PSMA PET/CT and mpMRI.

Significant and transition

Recent years have seen a significant shift in the diagnostic landscape of localised prostate cancer. Multiparametric MRI (mpMRI) is now a well-established tool in the assessment of primary tumours, and has demonstrated high sensitivity and excellent negative predictive values for clinically significant disease (1), leading to increasing uptake of pre-biopsy mpMRI
and targeted prostate biopsy (2-4).

Contemporary diagnostic biopsy; therefore, relies on precise identification of index tumour location on imaging. An index tumour is conventionally regarded as the focus of intra-prostatic cancer with highest grade; and  carries important clinical implications from a prognostic standpoint (5). Moreover, knowing index tumour location adds value to diagnostic and therapeutic approaches, including target biopsy and treatment.

Focus of intra-prostatic cancer

Despite its accuracy; some concerns remain around underestimation of tumour size and identification of transition zone lesions using mpMRI (6,7). 68Gallium labelled prostate-specific membrane antigen positron emission tomography (68GaPSMA PET) has emerged as a viable staging tool alongside mpMRI (8,9). PSMA is a transmembrane protein found on prostatic cells and overexpressed in prostate cancer (10); and targeting this using 68Ga-PSMA PET/CT has shown promise in accurately re-staging recurrent disease (11,12) and improving detection of lymph node metastases when compared with mpMRI (13-15).

Still, beyond evidence for its utility in advanced disease, the added potential of PSMA PET/CT in detecting and characterising primary prostate cancer lesions remains to be fully explored (16,17); along with any clinical benefit it offers over
mpMRI.