Prostate cancer is the uncontrolled growth of cells in the prostate, a gland in the male reproductive system just below the bladder. Early prostate cancer usually causes no symptoms. As the cancer develops, one or more tumors can damage nearby organs causing erectile dysfunction, blood in the urine or semen, and trouble urinating. For some patients, the cancer eventually spread to other areas of the body, particularly the bones and lymph nodes. There, tumors cause severe bone pain, leg weakness or paralysis, and eventually death.
Most cases of prostate cancer are detected after screening tests – typically blood tests for levels of prostate-specific antigen (PSA) – indicate unusual growth of prostate tissue. A definitive diagnosis requires a biopsy of the prostate, which is examined by a pathologist under a microscope. If cancer is present, the pathologist assigns a Gleason score of 6 to 10, with higher scores representing a more dangerous cancer disease. Medical imaging is performed to look for cancer spread outside the prostate. Based on the Gleason score, PSA levels, and imaging results, a cancer case is assigned a stage 1 to 4. Higher stage signifies a more advanced, more dangerous disease. Prostate cancer is different from all other common cancers in that as many as three out of four patients have more than one primary cancer focus. The different tumor foci have different properties, including sets of somatic mutations, which complicates the diagnostics and prognostication of the disease.
Most prostate tumors remain small and cause no health problems. These are managed with active surveillance, monitoring the tumor with regular tests to ensure it has not grown. Tumors more likely to be dangerous can be destroyed with radiation therapy or surgically removed by radical prostatectomy. Those whose cancer returns or has already spread beyond the prostate, are treated with hormone therapy that reduces levels of the androgens (male sex hormones) that prostate cells need in order to survive. This halts tumor growth for a while, but eventually cancer cells grow resistant to this treatment. This most-advanced stage of the disease, called castration-resistant prostate cancer, is treated with continued hormone therapy alongside the chemotherapy drug docetaxel. Prostate cancer prognosis depends on how far the cancer has spread at diagnosis and on particular biological properties of the cancer cells. Most men are diagnosed with tumors confined to the prostate; 99% of them survive more than 10 years from their diagnoses. Tumors that have metastasized to distant body sites are most dangerous, with five-year survival rates of 30–40%.
The risk of developing prostate cancer increases with age; the average age of diagnosis is 67. Those with a family history of prostate cancer are more likely to have prostate cancer themselves. Each year 1.2 million cases of prostate cancer are diagnosed, and 350,000 die of the disease, making it the second-leading cause of cancer and cancer death in men. One in eight men is diagnosed with prostate cancer in his lifetime, while one in forty dies of the disease. Prostate tumors were initially thought to be rare, with an 1893 report describing just 50 cases in the medical literature. As surgery became more common, prostate tumors were found in surgical specimens from enlarged prostates. Surgery and radiation therapy methods to treat the disease were developed over the course of the 20th century. Major work describing prostate tumors' need for male sex hormones, and the subsequent development of hormone therapies for prostate cancer, earned Charles B. Huggins the 1966 Nobel Prize in Physiology or Medicine, and Andrzej W. Schally the 1977 Nobel Prize in Physiology or Medicine.
Signs and symptoms
Most cases of prostate cancer are diagnosed through screening tests, when tumors are too small to cause any symptoms. As a tumor grows beyond the prostate, it can damage nearby organs causing erectile dysfunction, blood in the urine or semen, or trouble urinating – often frequent urination and slow or weak urine stream. More than half of men over age 50 experience some form of urination problem, typically due to issues other than prostate cancer such as benign prostatic hyperplasia (non-cancerous enlargement of the prostate).
Advanced prostate tumors often metastasize to nearby bones of the pelvis and back; there they can cause fatigue, unexplained weight loss, and back or bone pain that does not improve with rest. Metastases can damage the bones around them, and around a quarter of those with metastatic prostate cancer develop a bone fracture. Growing metastases can also compress the spinal cord causing weakness in the legs and feet, or limb paralysis.
