Treatment for metastatic hormone-sensitive prostate cancer is risk-classified according to the number of bone metastases. In the CHAARTED trial, 4 or more are defined as high volume. Recognizing ≥4 bone metastases at the time of diagnosis is an important indicator when selecting treatment. Conventional bone scintigraphy is used as a modality for detecting bone metastases, but currently, the use of SPECT, DWIBS, PET, etc. is increasing. In this study, we will examine the risk factors of ≥4 bone metastases patients, and for high-risk patients, we will proceed with bone metastasis diagnosis using new image.

Of the 782 men who underwent prostate biopsy at Showa University Hospital from January 2017 to December 2021, 524 were diagnosed with prostate cancer. Of the above, 452 patients who underwent MRI and bone scintigraphy were the subjects of this study. MRI and bone scans were evaluated by the same radiologist.

Twenty people died from prostate cancer. A significant difference was observed in the number of bone metastases (<4 vs ≥4) in cause specific survival (HR 18.36, p < 0.01, 95% CI (7.428 – 45.363)). PSA, ISUP grade group, PIRADS score, MRI tumor length, and pathological tumor length at biopsy were significantly associated with ≥4 bone metastasis in logistic regression.

PSA, ISUP grade group, PIRADS score, MRI tumor length, and pathological tumor length at biopsy were significantly associated with ≥4 bone metastasis at initial diagnosis of prostate cancer. We considered that we proceeded with bone metastasis diagnosis using new image for the patients who had risk factors.