Gallium-68 (68Ga)-Labelled Prostate-Specific Membrane Antigen Positron Emission Tomography/Computed Tomography in the Initial Staging of High-Risk Prostatic Adenocarcinoma: Reclassification to Oligometastatic Disease and Change in Treatment Intent.

Authors

Carlos Paul Villalba-Meneses, Adriana P Noboa, Veronica Marcela Villegas-Paredes

Published in

Cureus. Volume 18. Issue 9. Pages e116379. Epub Sep 16, 2026.

Abstract

Prostate cancer is among the most frequently diagnosed malignancies worldwide. In high-risk disease, conventional imaging underestimates nodal and skeletal extent, so treatment intent may be defined on incomplete staging. Positron emission tomography (PET) with gallium-68 (68Ga)-labelled prostate-specific membrane antigen (PSMA) ligands has shown superior diagnostic accuracy in this setting. A 69-year-old man, Eastern Cooperative Oncology Group (ECOG) performance status 0, presented with urinary symptoms and a rising prostate-specific antigen, from 18.2 to 34.1 ng/mL, with a doubling time under three months. Multiparametric magnetic resonance imaging (MRI) showed a Prostate Imaging-Reporting and Data System (PI-RADS) 5 lesion with extraprostatic extension, and biopsy of 12 cores (six per lobe) demonstrated acinar adenocarcinoma, Gleason 8 (4+4), International Society of Urological Pathology (ISUP) grade group 4, with perineural invasion and involvement of five of six left-sided cores; all six right-sided cores were tumor-free. PET/computed tomography (CT) was performed on a digital Siemens Biograph Vision 450 (Erlangen, Germany) after intravenous administration of 110.63 MBq (2.99 mCi) of 68Ga-PSMA imaging and therapy (I&T), with acquisition at 70 minutes and a delayed thoracic study. Images were read using the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) V2 criteria with molecular imaging Tumor, Node, Metastasis (miTNM) staging. With background references of standardized uptake value normalized to lean body mass (SUL) 1.2 for blood pool, 4.0 for liver, and 20.1 for parotid gland, the left-lobe prostatic lesion showed SUL 10.6, PSMA-expressing tumor volume (PSMA-TV) 10.09 cc, and PSMA total lesion (PSMA-TL) 53.23, with a PRIMARY score of 4. A 15 mm left internal iliac node with SUL 6.9, an 8 mm para-aortic node with SUL 3.2, and a 6 mm blastic lesion in the right sixth anterior costal arch with SUL 1.4, rising to 1.5 on delayed imaging, were identified. Whole-body tumor burden was PSMA-TV 15.09 cc and PSMA-TL 60.9. Staging was miT3a, miN1, miM1a, and unifocal miM1b, the latter based on an indeterminate bone lesion. The original treatment plan, prostate and pelvic radiotherapy with short-course androgen blockade and locoregional curative intent, was replaced by androgen deprivation with enzalutamide, prostate and pelvic radiotherapy, and stereotactic body radiotherapy to the para-aortic node and the costal lesion. Prostate-specific antigen fell to 0.15 ng/mL at three months and to undetectable levels at the six-month assessment. Molecular imaging reclassified disease regarded as high-risk localized as presumed low-volume oligometastatic and changed treatment intent from locoregional curative to intensified systemic therapy with metastasis-directed radiotherapy, with an early deep biochemical response on follow-up, which does not by itself establish durable oncological control.

PMID:
42890995
Bibliographic data and abstract were imported from PubMed on 18 Oct 2026.

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