The researchers took a cohort of 430 men with a biochemical recurrence (PSA increase only) after failed prostatectomy. The men underwent observation until they experienced metastatic disease as determined by CT or bone scan. The researchers then evaluated the PSA at the time the men developed metastasis for those patients who developed metastatic disease.

PSA at metastasis was defined as the PSA value at the time of the first occurrence of metastasis. The median PSA at metastasis was calculated and the interquartile range (IQR) for the entire cohort of men with metastatic progression as well as across different strata of PSADT (?3 vs 3-9 vs 9