Former President Joe Biden has been diagnosed with prostate cancer, his office has said. A statement issued by Biden's office on Sunday (May 18) revealed the 82-year-old was diagnosed after experiencing urinary issues. It said Biden has been diagnosed with an 'aggressive' form of the disease, which affects the prostate, and that the cancer has already spread to his bones. The news comes nearly a year after Biden was forced to drop out of the 2024 US presidential election over concerns about his health and age. The statement said: "Last week, President Joe Biden was seen for a new finding of a prostate nodule after experiencing increasing urinary symptoms. "On Friday, he was diagnosed with prostate cancer, characterised by a Gleason score of 9 (Grade Group 5) with metastasis to the bone. "While this represents a more aggressive form of the disease, the cancer appears to be hormone-sensitive which allows for effective management." Biden's office revealed his disease has a Gleason score of nine out of ten – but what is a Gleason score? And what does it mean for a cancer to be hormone-sensitive? The Gleason scoring system is a tool used to determine the severity of prostate cancer , the most common cancer affecting men. The aggressiveness score helps doctors to select appropriate treatments for patients and is calculated using samples of prostate cancer cells taken during a tumour biopsy. Different regions of the tumour can have different cancer cells present with different Grades – Grade one being the least aggressive and Grade five the most aggressive. An overall Gleason score by adding together the two most common grades. Patients with a Gleason score of six or less are considered low risk and may not require immediate treatment. According to Cancer Research UK, a Gleason score of nine or 10 means that "The cells look very abnormal. The cancer is likely to grow quickly." This score is deemed high-risk and advanced, indicating that Biden's cancer is very aggressive and will require extensive treatment. The five-year survival rate for metastatic prostate cancer, meaning it has spread to other parts of the body is 37 per cent, significantly lower than early-stage detection, according to the American Cancer Society (ACS). Treatment for advanced prostate cancer might include surgery, radiation therapy, hormone therapy and occasionally chemotherapy. Prostate cancers that are 'hormone-sensitive' need male sex hormones, such as testosterone, to grow, making this a key treatment. Hormone therapy works by either stopping the body from making testosterone, or by stopping testosterone from reaching cancer cells. This therapy is often used in conjunction with other treatments such as radiation or surgery, and has common side effects such as erectile dysfunction, weight gain, fatigue and osteoporosis, which causes bones to become brittle. For patients whose prostate cancer has spread to their bones, treatment typically aims to stop the cancer from spreading further and reducing symptoms, rather than curing the disease. Prostate cancer begins in the prostate, a small golf ball-sized gland below the bladder in the male reproductive system. The disease typically develops slowly over many years. It is often referred to as a 'silent killer' because symptoms do not usually appear until the prostate is large enough to affect the urethra – the tube carrying urine from the bladder out of the penis. Around 55,000 cases of prostate cancer are diagnosed each year in the UK. Most cases develop in men over the age of 50, with the disease more common in black men. The NHS says common symptoms of prostate cancer include: Prostate Cancer UK warns that the cancer can spread to other parts of the body, which may result in symptoms such as