Comparison of current screening methods in prostate cancer staging

Objective: Prostate cancer is ranked 2nd among the most common cancers in men and 6th among the causes of cancer-related deaths. Prostate cancer most commonly metastasizes to the skeletal system and lymph nodes. Bone scintigraphy is the most commonly used method to screen for bone metastases. Pelvic MRI and CT are used to screen for lymph node metastasis. Since prostate cancer cells show intense PSMA expression, bone metastases can be detected with high diagnostic accuracy by Ga68 PSMA Pet/Bt examination. Our aim is to compare the effectiveness of bone scintigraphy and Ga68 PSMA Pet/Bt in skeletal system screening in patients followed up for prostate cancer and to prevent unnecessary additional imaging methods. Materials and Methods: The data of 148 patients who underwent Ga68 PSMA PET/CT and bone scintigraphy at Zonguldak Bülent Ecevit University Faculty of Medicine, Department of Nuclear Medicine, between 2015 and 2023 for initial staging before treatment, staging during biochemical recurrence after curative treatment, or for metastatic evolution and control during follow-up if it was metastatic at the time of initial diagnosis were retrospectively examined from the hospital data system. These imaging results were interpreted by the faculty members of Zonguldak Bülent Ecevit University Faculty of Medicine Hospital, Department of Nuclear Medicine. Patients with a maximum interval of 120 days between two imaging studies were included in the study. In Ga68 PSMA PET/CT and bone scintigraphy reports, the locations and numbers of skeletal system metastases were evaluated comparatively and reported as present, absent and suspicious. The patients' 2005 modified Gleason scoring, PSA values and DRE findings were obtained, minimum 6-month and maximum 48-month PSA follow-ups along with the treatments they received after these examinations were noted, our goal was to understand which imaging method is more effective in predicting metastasis and to understand these methods' false positivity rates. Results: Data of 148 patients that underwent bone scintigraphy and Ga68 PSMA PET/CT imaging were retrospectively examined. Ga68 PSMA PET/CT and bone scintigraphy were taken in 89 (60.13%) of 148 patients at the time of diagnosis, for metastatic screening before treatment and in 59 (39.86%) patients during follow-up due to biochemical recurrence after treatment. Bone scintigraphy and Ga-68 PSMA PET/CT findings were reported differently in 31 of the 148 patients included in the study. In 117 patients, both imaging methods were reported to be similar. In 26 patients whose bone scintigraphy and Ga68 PSMA PET/CT findings were reported to be different, no metastasis was detected in the Ga-68 PSMA PET/CT performed after the bone scintigraphy was reported as suspicious, while in 5 patients metastasis was detected on Ga68 PSMA PET/CT despite there being no involvement in the bone scintigraphy. In 53 patients no metastasis was detected in both imaging methods, and in 64 patients, metastasis was detected in both imaging methods. If Ga68 PSMA PET/CT is accepted as the gold standard in showing bone metastases, the sensitivity rate of bone scintigraphy is 64/69 (92.75%), the specificity rate is 53/79 (67.08%), and the positive predictive value is 64/90 (71%). 11) negative predictive value was found to be 53/58 (91.37%). Ga68 PSMA PET/CT was found to be superior to bone scintigraphy in accurately predicting bone metastasis. 90 patients with metastasis detected on bone scintigraphy were divided into low, medium and high risk groups. When the bone scintigraphy positivity results were evaluated according to risk groups, it was seen that the high risk group gave true positive results at a statistically significant level (p: 0.001>). Conclusions: Accurate detection of metastasis status of patients followed up for prostate cancer is important for treatment planning. Bone scintigraphy is the most common and low-cost method used to screen for skeletal system metastases. However, due to the high false-positivity rate and the inability to fully identify suspicious lesions, additional examinations are required and this delays the treatment of patients. Ga68 PSMA PET/CT is more prominent in terms of accurately detecting bone metastases and other metastatic lesions in prostate cancer, and this seems more promising in terms of treatment planning.