What Is Prostate Cancer? Symptoms, Causes, Diagnosis, Stages, and Treatment

Prostate cancer is a disease in which cells in a man’s prostate gland grow out of control. The prostate is a small, walnut-sized gland below the bladder. It makes some of the fluid found in semen. Many prostate cancers grow slowly and stay inside the gland for years. Some grow faster, spread to other parts of the body, and need active treatment.

What Happens in the Prostate When Cancer Starts?

A side-by-side medical diagram comparing a healthy normal prostate gland with early prostate cancer. The image shows the bladder, rectum, and urethra, highlighting that early cancer cells grow on the outer edge of the prostate without blocking urine flow.
Understanding how prostate cancer starts: The diagram on the left shows a healthy prostate with normal urine flow. The diagram on the right shows early cancer cells forming a small lump on the outer edge of the gland, away from the urine tube (urethra).

The prostate is a small gland that helps make fluid for semen. When cancer starts, some prostate cells stop following the normal rules of growth and repair.

How Normal Prostate Cells Become Cancer Cells

Every cell in the body has DNA. DNA carries instructions that tell a cell when to grow, divide, repair itself, and die. Sometimes these instructions become damaged. These changes are called mutations.

When mutations build up in prostate cells, the cells may stop behaving normally. Healthy cells grow old and die when they should. Cancer cells do not. They keep dividing and making more abnormal cells. Over time, these extra cells can form a lump of tissue called a tumor.

Why Prostate Cancer Often Grows Slowly

Most prostate cancers do not appear overnight. They usually take many years to grow. Prostate cells often divide more slowly than cells in many other parts of the body. Even after they become cancer cells, many still grow at a slow pace.

Because of this, some prostate cancers never cause symptoms or serious harm during a man’s lifetime. Doctors often call these cancers slow-growing or indolent. Many men with slow-growing prostate cancer live for many years and die from other causes, not from prostate cancer.

Why Some Prostate Cancers Become Dangerous

Not all prostate cancers behave the same way. Some have more serious DNA changes. These cancers may grow faster and become aggressive.

Aggressive cancer cells can break away from the main tumor. They can move through the blood or lymph vessels. Lymph vessels are small channels that carry fluid through the body. If cancer cells reach other areas, such as bones, lymph nodes, liver, or lungs, they can start growing there. This spread is called metastasis. Metastasis is what makes prostate cancer more dangerous.

Comparison of Prostate Cancer Behavior Types

How the Cancer Behaves Growth Speed Early Symptoms Typical Medical Approach
Slow-Growing (Indolent) Takes many years to grow and often stays inside the prostate. Usually none. The body may function normally. Active Surveillance: Doctors monitor it closely with PSA tests, exams, MRI scans, and sometimes repeat biopsies. Treatment starts only if the cancer changes.
Fast-Growing (Aggressive) Grows faster and may spread beyond the prostate. May cause urinary changes, blood in urine or semen, or bone pain if advanced. Active Treatment: Doctors may use surgery, radiation, hormone therapy, chemotherapy, targeted therapy, or other treatments.

Where Does Prostate Cancer Usually Begin?

To understand prostate cancer, it helps to know where it usually starts inside the prostate. The prostate is made of different areas called zones.

The Outer Zone of the Prostate and Cancer Risk

Most prostate cancers start in the outer part of the prostate. Doctors call this the peripheral zone. This area sits closest to the rectum and makes up much of the prostate gland.

A normal adult prostate is often about the size of a walnut. It is usually about 4 centimeters (1.6 inches) wide and weighs about 20 grams (0.7 ounces), though size can vary. About 70% of prostate cancers begin in the peripheral zone.

Because this zone is near the rectum, a doctor may feel part of it during a digital rectal exam. The exam can sometimes find a hard area, lump, or change in shape. However, it cannot rule out prostate cancer by itself because some cancers cannot be felt.

Why Prostate Cancer May Not Affect Urination Early

The urethra is the tube that carries urine from the bladder out of the body. It passes through the middle of the prostate. Most prostate cancers start away from this central tube, in the outer zone.

Because of this, early prostate cancer often does not press on the urethra. Urine flow may stay normal. A man can have early prostate cancer for years without noticing any change in urination.

How Cancer Can Grow Beyond the Prostate

If an aggressive cancer keeps growing, it may reach the edge of the prostate. The prostate has an outer layer of tissue around it. Cancer can grow through this layer and move into nearby areas.

The seminal vesicles are small glands behind and above the prostate. They help make semen. Prostate cancer can spread into the seminal vesicles. It can also grow toward nearby tissues, such as the bladder, rectum, pelvic wall, or nearby lymph nodes.

What Are the Most Common Prostate Cancer Symptoms?

Prostate cancer symptoms depend on the size of the tumor and whether the cancer has spread. Early prostate cancer often causes no symptoms at all.

Why Early Prostate Cancer Often Has No Symptoms

In the early stages, prostate cancer usually does not cause pain or warning signs. The tumor is often too small to affect nearby tissues. Since it usually starts in the outer part of the prostate, it may not block urine flow.

A man can feel healthy and still have prostate cancer. For this reason, prostate cancer is often found through PSA testing, imaging, or biopsy, not through symptoms.

Urinary Symptoms That May Need Testing

If a tumor becomes large, or if cancer starts closer to the urethra, it may narrow the urine passage. This can make it harder for the bladder to empty.

Possible urinary symptoms include:

  • Passing urine more often
  • Waking up at night to urinate
  • Trouble starting urination
  • A weak urine stream
  • A urine stream that starts and stops
  • Feeling that the bladder has not fully emptied

These symptoms do not always mean cancer. Benign prostate enlargement and prostate inflammation can cause similar symptoms. Testing is needed to find the cause.

Symptoms That May Suggest Advanced Prostate Cancer

Advanced prostate cancer can cause symptoms in other parts of the body. Prostate cancer most often spreads to bones. This can cause deep, ongoing pain in the hips, lower back, ribs, or other bones.

Other possible signs of advanced disease include:

  • Blood in the urine
  • Blood in the semen
  • Unexplained weight loss
  • Severe tiredness
  • Swelling in the legs if lymph flow is blocked

What Causes Prostate Cancer?

The exact cause of prostate cancer is not known in every case. It usually develops when DNA changes build up in prostate cells over time. Some risk factors make prostate cancer more likely.

Age and Prostate Cancer Risk

Age is the strongest risk factor for prostate cancer. The disease is rare in men under 40. Risk rises after age 50 and is highest in older men.

Many prostate cancers are found in men aged 65 or older. As the body ages, prostate cells have had more time to divide and collect DNA changes. Over many years, these changes can lead to cancer.

Family History and Inherited Risk

Family history can raise a man’s risk. A man has a higher risk if his father, brother, or son has had prostate cancer. The risk is higher if more than one close relative had prostate cancer or if the cancer was diagnosed at a young age.

Some inherited gene changes can also increase risk. Changes in the BRCA1 or BRCA2 genes are best known for raising breast and ovarian cancer risk, but they can also increase prostate cancer risk in men. Other inherited gene changes may also play a role.

Risk also differs by ancestry. Men of African ancestry have a higher risk of prostate cancer and are more likely to develop aggressive disease. The reasons are complex and may include genetics, access to care, social factors, and other health differences.

Lifestyle Factors That May Influence Risk

Daily habits may affect prostate cancer risk and outcomes, although the link has not been established conclusively. A diet high in red meat, processed meat, and high-fat dairy, and low in vegetables and fruit, may be linked with higher risk in some studies.

Obesity is more clearly linked with worse prostate cancer outcomes. Men with obesity may be more likely to develop aggressive prostate cancer and may have a higher risk of the cancer returning after treatment.

Healthy habits cannot guarantee prevention, but they support overall health. These include staying active, keeping a healthy weight, eating a balanced diet, and not smoking.

How Is Prostate Cancer Found and Diagnosed?

Prostate cancer is usually found through a step-by-step process. Doctors may use PSA blood testing, a prostate exam, MRI scans, and biopsy. A biopsy is the only way to confirm the diagnosis.

PSA Blood Test as a First Clue

PSA stands for prostate-specific antigen. It is a protein made by prostate cells. Both normal prostate cells and prostate cancer cells can make PSA.

A PSA test measures the amount of PSA in the blood. PSA is commonly reported as nanograms per milliliter, written as ng/mL. Some labs report the same value as micrograms per liter, written as µg/L. These units are equivalent: 1 ng/mL equals 1 µg/L.

A raised PSA does not always mean cancer. PSA can rise because of prostate enlargement, prostate inflammation, infection, recent procedures, age, and some medicines. However, a high or rising PSA can be an important clue that more testing may be needed.

MRI and Biopsy Before Diagnosis Is Confirmed

If the PSA is high, rising, or concerning, doctors may recommend a multiparametric MRI scan, often called mpMRI. This scan makes detailed pictures of the prostate. It can show areas that look suspicious for cancer.

If the MRI shows a suspicious area, or if other findings are concerning, a prostate biopsy may be done. During a biopsy, a doctor removes small samples of prostate tissue with a thin needle. Samples may be taken from the suspicious area and from other parts of the prostate.

A biopsy is the only way to confirm prostate cancer.

Pathology Results That Confirm Cancer

The biopsy samples are sent to a laboratory. A pathologist examines the tissue under a microscope.

Healthy prostate cells usually appear organized. Cancer cells often look crowded, uneven, and disorganized. If the pathologist sees cancer, the report will confirm the diagnosis. The report also gives important details about how aggressive the cancer looks.

How Is Prostate Cancer Staged and Graded?

After prostate cancer is confirmed, doctors need to know how far it has spread and how aggressive it looks. This is done through staging and grading.

Stage Shows Where the Cancer Is

Staging describes where the cancer is in the body. It shows whether the cancer is still inside the prostate, has spread nearby, or has spread to distant areas.

Doctors often use stages 1 to 4.

  • Stage 1 means the cancer is small and only inside the prostate. It may not be felt during a prostate exam.
  • Stage 2 means the cancer is still inside the prostate but may be larger or involve more of the gland.
  • Stage 3 means the cancer has grown through the outer edge of the prostate or into nearby tissues, such as the seminal vesicles.
  • Stage 4 means the cancer has spread to nearby lymph nodes or to distant parts of the body, such as bones, liver, or lungs.

Grade Shows How Aggressive the Cancer Looks

Grading shows how abnormal the cancer cells look under the microscope. It helps predict how quickly the cancer may grow or spread.

Doctors use the Gleason scoring system. The pathologist looks at the two most common cancer cell patterns and gives each a score from 3 to 5. These two numbers are added together. Most prostate cancers found on biopsy have Gleason scores from 6 to 10.

  • A Gleason score of 6 is low grade. The cells look more like normal prostate cells and usually grow slowly.
  • A Gleason score of 7 is intermediate grade. These cancers may grow more quickly than low-grade cancers.
  • Gleason scores of 8 to 10 are high grade. These cells look very abnormal and are more likely to grow and spread.

Many reports also use Grade Groups from 1 to 5. Grade Group 1 is the least aggressive. Grade Group 5 is the most aggressive.

Risk Groups Help Guide Treatment Choices

Doctors combine the PSA level, Gleason score or Grade Group, stage, MRI results, biopsy findings, and overall health to place the cancer into a risk group. These groups may be very low, low, intermediate, high, or very high risk.

Risk groups help guide treatment. Low-risk prostate cancer may be watched closely with active surveillance. Higher-risk cancer often needs active treatment. This approach helps avoid overtreatment for slow cancers while treating aggressive cancers early.

What Are the Main Treatment Options for Prostate Cancer?

There is no single best treatment for every man with prostate cancer. Treatment depends on the cancer’s risk group, stage, grade, PSA level, age, overall health, and personal preferences.

Monitoring Low-Risk Prostate Cancer

For many men with low-risk prostate cancer, active surveillance is often a good option. This means the cancer is monitored closely instead of treated right away.

Active surveillance may include regular PSA tests, prostate exams, MRI scans, and repeat biopsies. The goal is to avoid side effects from treatment unless the cancer shows signs of growing or becoming more aggressive.

This is different from ignoring the cancer. Active surveillance is a planned medical approach with regular follow-up.

Treating Cancer Confined to the Prostate

If prostate cancer is still inside the prostate but has a higher risk of growing, treatment may aim to cure it.

One option is radical prostatectomy. This surgery removes the whole prostate gland and some nearby tissue. In some cases, nearby lymph nodes are also removed.

Another option is radiation therapy. External beam radiation uses high-energy rays from outside the body to kill cancer cells. Brachytherapy is internal radiation. It places small radioactive seeds or sources in or near the prostate.

Some men may have radiation with hormone therapy. The best choice depends on the cancer features and the person’s overall health.

Treating Cancer That Has Spread

If prostate cancer has spread outside the prostate to distant areas, treatment needs to work throughout the body.

Prostate cancer cells often depend on male hormones called androgens, especially testosterone, to grow. Androgen deprivation therapy, or hormone therapy, lowers or blocks these hormones. This can slow cancer growth and shrink tumors.

Other treatments may include chemotherapy, newer hormone-blocking tablets, targeted therapy, immunotherapy, radiopharmaceutical therapy for cancer in the bones, and medicines to protect bone health. Treatment is chosen based on the cancer type, test results, symptoms, and previous treatments.

What Is the Outlook After a Prostate Cancer Diagnosis?

A prostate cancer diagnosis can be frightening. However, the outlook is often very good, especially when the cancer is found before it spreads.

Why Many Men Live for Years After Diagnosis

Many prostate cancers grow slowly. When prostate cancer is found while still localized or regional, the five-year relative survival rate is very high, above 99%.

This does not mean every case is the same. Survival depends on the stage, grade, PSA level, response to treatment, age, and other health problems. Still, many men with prostate cancer live for many years after diagnosis.

Why Stage and Grade Matter More Than Fear

The word cancer can cause fear, but prostate cancer is not one single disease. A small, low-grade cancer inside the prostate is very different from a high-grade cancer that has spread.

The most important details are the PSA level, biopsy result, Gleason score or Grade Group, MRI findings, and stage. These facts help the medical team choose the safest and most useful care plan.

How Follow-Up Tests Track the Cancer Over Time

Follow-up testing is important after any prostate cancer plan, including active surveillance, surgery, radiation, or hormone therapy. PSA blood tests are often used to track the cancer over time.

After the prostate is removed, PSA usually falls to a very low or undetectable level. After radiation, PSA usually falls more slowly and settles at a low level. A rising PSA may mean that more testing is needed. Regular follow-up helps doctors find changes early and adjust treatment if needed.

Written by Chris Morais, MSc, MPhil, PhD — Making complex health information simple.

Sources & Further Reading

  1. National Cancer Institute. Prostate Cancer Treatment (PDQ®)–Patient Version. Bethesda, MD: National Institutes of Health. Available from: https://www.cancer.gov/types/prostate/patient/prostate-treatment-pdq
  2. American Cancer Society. About Prostate Cancer. Atlanta, GA: American Cancer Society. Available from: https://www.cancer.org/cancer/types/prostate-cancer/about.html
  3. Centers for Disease Control and Prevention. Prostate Cancer. Atlanta, GA: CDC. Available from: https://www.cdc.gov/cancer/prostate/index.htm
  4. Mayo Clinic. Prostate cancer: Symptoms & causes. Rochester, MN: Mayo Foundation for Medical Education and Research. Available from: https://www.mayoclinic.org/diseases-conditions/prostate-cancer/symptoms-causes/syc-20353087
  5. Urology Care Foundation. What is Prostate Cancer? Linthicum, MD: American Urological Association. Available from: https://www.urologyhealth.org/urology-a-z/p/prostate-cancer
  6. Harvard Health Publishing. Prostate Cancer: A guide to identification and treatment. Boston, MA: Harvard Medical School. Available from: https://www.health.harvard.edu/a-to-z/prostate-cancer-a-to-z
  7. World Health Organization. Cancer. Geneva: WHO. Available from: https://www.who.int/news-room/fact-sheets/detail/cancer
  8. National Health Service. Prostate cancer. London: NHS. Available from: https://www.nhs.uk/conditions/prostate-cancer/
  9. Johns Hopkins Medicine. Prostate Cancer. Baltimore, MD: The Johns Hopkins University. Available from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/prostate-cancer

Note: External links were verified when published but may change over time, which is beyond our control.

Disclaimer: This educational content does not constitute medical advice. Always consult a qualified physician or urologist for personal health concerns or diagnostic decisions.

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