Biden was having increasing urinary symptoms and was seen last week by doctors who found a prostate nodule. On Friday, he was diagnosed with prostate cancer and the cancer cells have spread to the bone, his office said in a statement.

When caught early, prostate cancer is highly survivable, but it is also the second-leading cause of cancer death in men. About one in eight men will be diagnosed over their lifetime with prostate cancer, according to the American Cancer Society.

Here are some things to know about prostate cancer that has spread.

What is the prostate gland?

The prostate is part of the reproductive system in men. It makes fluid for semen. It’s located below the bladder and it wraps around the urethra, the tube that carries urine and semen out through the penis.

How serious is Biden’s cancer?

Biden’s cancer has spread to the bone, his office said. That makes it more serious than localized or early-stage prostate cancer.

Outcomes have improved in recent decades and patients can expect to live with metastatic prostate cancer for four or five years, said Dr. Matthew Smith of Massachusetts General Brigham Cancer Center.

“It’s very treatable, but not curable,” Smith said.

What are the treatment options?

Prostate cancer can be treated with drugs that lower levels of hormones in the body or stop them from getting into prostate cancer cells. The drugs can slow down the growth of cancer cells.

“Most men in this situation would be treated with drugs and would not be advised to have either surgery or radiation therapy,” Smith said.

What is a Gleason score?

Prostate cancers are graded for aggressiveness using what’s known as a Gleason score. The scores range from 6 to 10, with 8, 9 and 10 prostate cancers behaving more aggressively. Biden’s office said his score was 9, suggesting his cancer is among the most aggressive.