Conventional imaging with computed tomography (CT), magnetic resonance imaging (MRI) and bone scans, are the current standard of care for imaging prostate cancer.¹Alipour R et al. Ther Adv Med Oncol. 2019;11. Accurate imaging primarily relies on nodal metastases size for detection.¹Alipour R et al. Ther Adv Med Oncol. 2019;11. However, a large proportion in prostate cancer nodal metastases are smaller than 8mm.¹Alipour R et al. Ther Adv Med Oncol. 2019;11. Radionuclide bone scans also lack sensitivity for detecting bone marrow lesions, a common site of distant metastases in prostate cancer.¹Alipour R et al. Ther Adv Med Oncol. 2019;11.

Prostate-specific membrane antigen (PSMA), a transmembrane protein with overexpression in prostate cancer cells, has emerged as a target molecule for imaging.²Maurer T et al. Nat Rev Urol. 2016;13(4):226-235. Small compounds labelling PSMA have been developed, including the ⁶⁸Gallium-labelled PSMA molecule that is now being investigated in PSMA PET-CT scanning.²Maurer T et al. Nat Rev Urol. 2016;13(4):226-235.

Results from the multicentre, two arm, randomised controlled proPSMA trial earlier this year reported PSMA PET-CT scans to be superior to conventional imaging for the primary staging of high-risk prostate cancer.³Hofman MS et al. The Lancet. 2020;395(10231):1208-1216. The study aimed to investigate if PSMA PET-CT could improve accuracy when compared to the combination of CT and bone scan.³Hofman MS et al. The Lancet. 2020;395(10231):1208-1216. The primary outcome was the accuracy of first-line imaging for identifying either pelvic nodal or distant-metastatic disease.³Hofman MS et al. The Lancet. 2020;395(10231):1208-1216. The PSMA PET-CT scans had a 27% absolute greater area under the curve (AUC) for accuracy than conventional imaging, which reflected the higher sensitivity and specificity of PSMA PET-CT.³Hofman MS et al. The Lancet. 2020;395(10231):1208-1216. Subgroups of patients with pelvic nodal and distant-metastatic disease also reflected these results.³Hofman MS et al. The Lancet. 2020;395(10231):1208-1216.

Recent data presented at the American Society for Radiation Oncology (ASTRO) Annual Meeting 2020 has also found that routinely collected clinical data can help identify men with high-risk prostate cancer most likely to benefit from regular PSMA PET scanning.⁴Ma MT. Presentation 58. Presented at American Society for Radiation Oncology Annual Meeting 2020. Available at: https://plan.core-apps.com/myastroapp2020/abstract/69f15c52-dce5-4388-ad8f-114043d836ca (Accessed 26 November 2020). A post-hoc analysis of 249 eligible patients with high- or very high-risk prostate cancer and who underwent a staging PSMA PET on a prospective trial found 22.9% of patients were upstaged by PSMA PET.⁴Ma MT. Presentation 58. Presented at American Society for Radiation Oncology Annual Meeting 2020. Available at: https://plan.core-apps.com/myastroapp2020/abstract/69f15c52-dce5-4388-ad8f-114043d836ca (Accessed 26 November 2020). Of patients with iN0 disease by CT or MRI, 18.9% of were found to have N1 disease by PSMA PET, and 10.6% of patients who had M0 disease by CT or bone scan were found to have M1 disease.⁴Ma MT. Presentation 58. Presented at American Society for Radiation Oncology Annual Meeting 2020. Available at: https://plan.core-apps.com/myastroapp2020/abstract/69f15c52-dce5-4388-ad8f-114043d836ca (Accessed 26 November 2020). Multivariate analysis indicated independent predictors of nodal and metastatic upstaging were higher percentages of positive cores at biopsy and higher Gleason score, and patients with positive cores ≥ 50% or with Gleason grade 4/5 would benefit most from a PSMA PET-CT.⁴Ma MT. Presentation 58. Presented at American Society for Radiation Oncology Annual Meeting 2020. Available at: https://plan.core-apps.com/myastroapp2020/abstract/69f15c52-dce5-4388-ad8f-114043d836ca (Accessed 26 November 2020).

The superior diagnostic accuracy of PSMA PET-CT over conventional imaging could change the standard of care for imaging in prostate cancer, and the results presented at the ASTRO Annual Meeting may help to stratify which patients would benefit most from this.