When everything is functioning as it should, you may not spend a lot of time thinking about your prostate, the walnut-sized gland that sits below the bladder and in front of the rectum. Found only in men, it surrounds the urethra—the tube through which both urine and semen pass—and plays an important role in the male reproductive system, producing the fluid that makes up part of semen.

But when something goes wrong with the prostate, it can cause worrying symptoms. Men may have a hard time starting the flow of urine, need to urinate more frequently than usual, and have a weak urinary stream. These and other symptoms are often caused by an enlarged prostate gland, but they can also result from prostate cancer, which, after skin cancer, is the most common form of cancer in men.

Prostate cancer most commonly occurs in men over age 65 and is rare in those under 40. The National Cancer Institute estimates that in 2021, nearly 250,000 men will be diagnosed with the disease and around 34,000 men will die from it. Around one out of every eight men will be diagnosed with it during their lifetime.

Though prostate cancer is common, the good news is that there are many treatments for it. If caught at an early stage, it has a good prognosis and, in some cases, can be cured.

Prostate cancer occurs when cells in the prostate gland grow and divide uncontrollably. Over time, these cells can form a mass of tissue called a tumor. In many cases, tumors are benign, meaning they are not cancerous and do not spread to other parts of the body. Sometimes, though, tumors are malignant, or cancerous. The cells that make up malignant tumors are capable of invading nearby tissues and spreading to distant parts of the body.

Prostate cancer usually grows and progresses slowly, though in some cases, it spreads aggressively and rapidly. In its early stages, when the cancer is small and has not invaded neighboring tissues or spread to other parts of the body, prostate cancer typically does not cause any symptoms. As it progresses and the tumor enlarges, however, symptoms may begin to develop. Cancer cells may break away from the tumor in the prostate and spread to the lymph nodes and other parts of the body. This is known as metastatic cancer. When prostate cancers metastasize, they often spread to the bones of the pelvis, ribs, or backbone where they can cause pain and other symptoms.

The strongest risk factors for prostate cancer include:

• Age (prostate cancer is rare in men under age 40 and risk goes up with increasing age)
• Family history of prostate cancer

Studies have identified other factors that may increase the risk for prostate cancer. These include:

• Having certain inherited genetic mutations including BRCA1, BRCA2, CHEK2, ATM, and PALB2 among others
• Lynch syndrome
• Diet (consuming high levels of dairy products, processed foods, calcium, and alcohol may increase risk)
• Obesity
• Cigarette smoking
• Exposure to certain chemicals such as Agent Orange
• Sexually transmitted infections (e.g., human papillomavirus (HPV), gonorrhea)

Early-stage prostate cancer often does not cause symptoms. When symptoms develop, they may include:

• Weak urinary stream
• Increased frequency of urination (especially at night)
• Increased urge to urinate
• Difficulty starting urination
• Urinary stream that starts and stops
• Inability to completely empty bladder of urine
• Blood in the urine or semen
• Pain during urination
• Pain in the back, pelvis, or hips
• Erectile dysfunction

Prostate cancer screening tests are used to detect cancer at an early stage, before symptoms begin. The prostate-specific antigen (PSA) blood test—the main screening test for prostate cancer—measures the level of PSA, a protein produced by the prostate gland, in the blood. PSA levels may be elevated in men who have prostate cancer. Doctors may also perform a digital rectal exam (DRE) to examine the prostate. In this procedure, the doctor inserts a gloved finger into the patient’s rectum and feels the prostate to check for abnormalities.

If a PSA blood test or DRE detect an abnormality, the doctor will order additional tests such as a biopsy or imaging tests to determine if the patient has prostate cancer.

Screening may be offered to men starting around age 50 or 55, though those who are at higher risk for prostate cancer may begin screening testing at age 40 or 45. Men should talk to their doctors about the risks and benefits of screening tests.

To begin diagnosis, your doctor will review your medical history, ask you about your symptoms, and whether you have any risk factors for prostate cancer. They will also perform a physical exam that usually involves a DRE.

Some additional tests are necessary for diagnosis. You may need to have a PSA blood test, even if you’ve had one within the past few weeks. Your doctor may also order one or more imaging tests such as an ultrasound. A biopsy, however, is necessary to definitively diagnose prostate cancer. One common method for performing a prostate biopsy is known as transrectal biopsy. In this procedure, a doctor will use MRI- or ultrasound-imaging to guide a thin needle to the prostate through the rectum. Using the needle, they will collect a small piece of prostate tissue. A pathologist then analyzes the tissue sample under a microscope to check for the presence of cancer cells.

If a doctor diagnoses prostate cancer, they will grade and stage the cancer. Grading and staging are done to determine the extent of the cancer, make a prognosis, and determine the best course of treatment.

• Grading. A pathologist will give the cancer a grade based on how abnormal the cancer cells look under a microscope. A cancer’s grade is used to predict how aggressively it is likely to spread. The lower the grade, the less likely the cancer is to spread aggressively.
• Stage. Doctors stage prostate cancer based on its grade, PSA test results, and additional imaging tests such as bone scan, computed tomography (CT) scan, or positron emission tomography (PET) scan. These imaging tests may involve the use of a small dose of radioactive material called a radiotracer to improve detection of cancer that has spread to the bones or elsewhere in the body. A lymph node biopsy may also be necessary. Doctors assign the cancer to a stage, usually numbered between I and IV. The lower the stage, the less extensive the cancer is and the better the prognosis.

Treatments for prostate cancer include:

• Active surveillance. Rather than provide immediate treatment, the cancer is monitored over time. This approach may be used for small, slow growing cancers, especially in older men. It requires regular checkups with a doctor for PSA, DREs, and other tests.
• Surgery. A prostatectomy, or the surgical removal of the prostate gland, may be an option for cancer that is localized to the prostate. In some cases, a surgeon will perform a type of surgery known as transurethral resection of the prostate (TURP). In TURP, the surgeon uses a tool called a resectoscope to remove prostate tissue through the urethra. Surgical removal of the lymph nodes may also be necessary to determine if cancer has spread to them.
• Radiation therapy. This treatment kills and damages cancer cells by exposing them to radiation. The radiation may be given via a machine located outside the body. This is known as external beam radiation therapy (EBRT). A similar technique called stereotactic body radiation therapy (SBRT) precisely delivers high doses of radiation to the prostate. Radiation can also be given using brachytherapy, a technique in which small radioactive “seeds” are implanted in the prostate. 
• Hormone therapy. Prostate cancer cells use hormones, called androgens, to grow. A type of hormone therapy called androgen deprivation therapy (ADT) is used to reduce androgen levels or block them from working, thereby slowing or stopping the growth of cancer cells. This may be accomplished with drugs, other hormones, and/or by the surgical removal of the testicles (which produce androgens).
• Chemotherapy. Chemotherapy uses drugs to destroy and damage cancer cells.
• Targeted therapy. This treatment uses drugs designed to target specific components of cancer cells that are not found in healthy cells.
• Immunotherapy. Immunotherapy drugs stimulate or suppress the patient’s own immune system to help it better fight cancer.
• Cryotherapy. In cryotherapy, a doctor inserts needles into the prostate. Cold gases are delivered to the prostate through the needles, resulting in the destruction of cancer cells.

The outlook for a man with prostate cancer varies based on a number of factors including the stage and grade of the cancer, how well it responds to treatments, and the man’s age and overall health. The prognosis is good for cancer that is confined to the prostate or has spread only to nearby tissues. At these stages of prostate cancer, the five-year survival rate is 100%, and in many cases, the cancer can be cured. Men with prostate cancer that has metastasized, or spread to distant parts of the body, however, have a poorer prognosis.