⁶⁸Ga-PSMA PET-CT in patients with newly diagnosed high- risk prostate cancer

Objectives Accurate staging of patients with high-risk prostate cancer is an ongoing imaging challenge being essential for appropriate treatment planning. ⁶⁸Ga-PSMA (Prostate- Specific Membrane Antigen) is a novel PET tracer recently introduced in imaging of prostate cancer. Publications have shown high diagnostic accuracy for its use in patients with biochemical failure after treatment. The aim of the current study was to assess its use in patients with high-risk cancer at diagnosis.

Methods ⁶⁸Ga-PSMA PET-CT was performed in 53 patients with newly diagnosed prostate cancer, Gleason score 7or higher. The study is retrospective. In 46 patients the treatment approach was available at the medical records.

Results All 53 patients had increased ⁶⁸Ga-PSMA uptake at the prostate. In only 17 patients (32%) uptake was localized only to the prostate gland. In 12 patients PET-CT findings suggested capsular involvement, in 6, seminal vesicles involvement and in 3, uptake was not separated from the rectum or urinary bladder wall. Thirty eight patients (72%) had increased lymph node uptake. In 28 patients nodal uptake was detected only in the pelvis (5 perirectal, 20 iliac chains, 3 superior rectal), in 7 also in retroperitoneal nodes and in 3 in mesenteric nodes. Three patients had nodal uptake also above the diaphragm. In 12 patients (23%) skeletal increased uptake was identified; intramedullary =1, cortical and intramedullary=2, and cortical =9. In 4 of the 12 patients the bone was the only site of uptake other than the primary tumor site. There was a single patient with uptake in lung nodules suggestive of metastasis. Of the 46 patients in whom we had treatment data, only 12 had surgery (26%); 10 patients with localized prostate uptake (in 3 with combination of radiation (R) and hormonal therapy (H)) and 2 with uptake also in pelvic lymph node dissected at surgery. In 25 patients (54%) treatment included R+H, seven patients received only hormonal therapy and two patients received chemotherapy.

Conclusions Patients presenting with high risk prostate cancer often have locally advanced disease, nodal involvement and remote metastasis mainly in bone. ⁶⁸Ga-PSMA PET-CT study allows staging having a potential impact on individual tailoring of treatment approach. ⁶⁸Ga-PSMA PET-CT findings may have a role in selection of patients which may benefit from treatment with ¹⁷⁷Lu-PSMA