Gallium-68-labeled prostate-specific membrane antigen (Ga-PSMA) positron emission tomography (PET)/computed tomography (CT) is a valuable diagnostic tool for the detection of bone metastases in patients with prostate cancer (PCa). However, bone scintigraphy (BS) with technetium-labeled diphosphonates is cheap and widely available for the same patient population. PSMA PET comes with a cost, and financial constraints in the present economic environment may require its more selective use. In this study, we aimed to compare the diagnostic performance of BS with Ga-PSMA PET/CT for the detection of bone metastases in patients with PCa and correlate the results with various clinical and biochemical variables.
Ninety-five patients who underwent Ga-PSMA PET/CT and BS within 3 months for newly diagnosed or recurrent PCa were extracted from our database. Lesion, region and patient-based analyses were performed. Clinical and imaging follow-up was used as the reference test. Results were compared with tumor grade, serum prostate-specific antigen (PSA), and alkaline phosphatase (ALP) values.
On the patient-based analysis, 75% (42/56) and 98.2% (55/56) of the patients with bone metastases were correctly diagnosed by BS and Ga-PSMA PET, respectively. In 26/95 patients with equivocal lesions on BS, Ga-PSMA PET correctly reclassified skeletal involvement in 11 and excluded metastases in 15 patients BS missed bone metastases in 3 patients. The true-positive rate of BS in patients with serum ALP ≥ 120U/L and PSA ≥ 50 ng/ml was 95.8% and 87.5 respectively.
Ga-PSMA is superior to BS for the evaluation of metastatic disease in patients with PCa. However, BS can also detect bone metastases in patients with PCa with a minimum sensitivity of 75%. Biochemical data are helpful to select patients with a high pretest probability who should undergo BS first as a part of the initial workup from an economic point of view. Due to its higher cost, Ga-PSMA PET should be performed in a selective group of patients when BS results are inconclusive or metastasis-directed therapy is planned.
Annals of nuclear medicine. 2020 Sep 25 [Epub ahead of print]
Meltem Caglar, Murat Tuncel, Egemen Yildiz, Erdem Karabulut
Department of Nuclear Medicine, Medical Faculty, Hacettepe University, Sıhhiye, 06100, Ankara, Turkey., Department of Nuclear Medicine, Medical Faculty, Hacettepe University, Sıhhiye, 06100, Ankara, Turkey. ., Department of Biostatistics, Medical Faculty, Hacettepe University, Ankara, Turkey.