According to the statement, Biden, 82, was diagnosed with cancer on Friday, May 16, upon a medical check after experiencing “increasing urinary symptoms.” It added that Biden’s cancer was characterized by a Gleason score of 9, with metastasis to the bone.

The Gleason score is a grading system for prostate cancer that rates tumors on a scale of six to 10. It is one of several diagnostic tools doctors use to understand a patient’s cancer and develop a treatment plan. Cancers on the low end of the scale grow slowly and are less likely to spread.