Highlight
Bone is one of major metastatic site in patients with genitourinary (GU) cancer.
Accurately predicting survival of patients with bone metastasis (BM) is essential.
This external validation study proved high predictive accuracy of B-FOM score.
B-FOM score is a simple scoring model based on five prognostic factors.
B-FOM score is higher accurate tool comparing to other previously reported scores.