How Does Cancer Spread? A Look at Metastatic Cancer

by Sarah Carpenter


Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body. But how and why does this happen? We will explore how cancer spreads, what causes cancer cell growth, the science behind it and the risks associated with metastasis. We’ll also touch on what can be done to slow the spread of cancer including treatment options like chemotherapy, radiation and surgery.

What Is Metastatic Cancer?

The process by which cancer cells spread to other parts of the body is called metastasis. Cancer that spreads is called metastatic cancer, often referred to as stage IV cancer. When observed under a microscope and tested in other ways, metastatic cancer cells have features like that of the primary cancer and not the cells in the place where the metastatic cancer is found. This is how doctors can tell that it is cancer that has spread from another part of the body.

How Does Cancer Spread?

Cancer cells spread through the body in a series of steps including:

  • Step 1. Growing into or invading nearby normal tissue.
  • Step 2. Moving through the walls of nearby lymph nodes or blood vessels.
  • Step 3. Traveling through the lymphatic system and bloodstream to other parts of the body.
  • Step 4. Stopping in small blood vessels at a distant location, invading the blood vessel walls and moving into the surrounding tissue.
  • Step 5. Growing in this tissue until a tiny tumor forms.
  • Step 6. Causing new blood vessels to grow which creates a blood supply that allows the metastatic tumor to continue growing.

Most of the time, spreading cancer cells die at some point in this process. As long as conditions are favorable for the cancer cells at every step, some of them can form new tumors in other parts of the body. Metastatic cancer cells can also remain inactive at a distant site for many years before they begin to grow again, if at all.

The Causes of Cancer Cell Growth and the Science Behind It
Cancer is caused by changes (mutations) to the DNA within cells. The DNA inside a cell is packaged into a large number of individual genes — each of which contains instructions telling the cell what functions to perform and how to grow and divide. Errors in the instructions can cause the cell to stop its normal function and may allow a cell to become cancerous. A gene mutation can instruct a healthy cell to:

  • Allow rapid growth. A gene mutation can tell a cell to grow and divide more rapidly. This creates many new cells that all have the same mutation.
  • Fail to stop uncontrolled cell growth. Normal cells know when to stop growing so that there is the right number for each type of cell. Cancer cells lose the controls (tumor suppressor genes) that tell them when to stop growing. A mutation in a tumor suppressor gene allows cancer cells to continue growing and accumulating.
  • Make mistakes when repairing DNA errors. DNA repair genes look for errors in a cell’s DNA and make corrections. A mutation in a DNA repair gene may mean that other errors aren’t corrected, leading cells to become cancerous.

These mutations are the most common ones found in cancer. However, many other gene mutations can contribute to causing cancer. Gene mutations can occur for several reasons, for instance:

  • Gene mutations you’re born with. You may be born with a genetic mutation inherited from your parents. This type of mutation accounts for a small percentage of cancers.
  • Gene mutations that occur after birth. Most gene mutations occur after you’re born and aren’t inherited. Instead, they occur during normal cell growth. Several forces can cause gene mutations, such as smoking, radiation, viruses, cancer-causing chemicals (carcinogens), obesity, hormones, chronic inflammation and a lack of exercise.

The gene mutations you’re born with, and those that you acquire throughout your life work together to form cancer. For instance, if you’ve inherited a genetic mutation predisposing you to cancer, that doesn’t mean you’re certain to get cancer. Instead, you may need one or more other gene mutations to cause cancer. Your inherited gene mutation could make you more likely than other people to develop cancer when exposed to a certain cancer-causing substance.

Risk Factors for Cancer Cell Growth

A risk factor increases a person’s chance of developing cancer or having it come back after it is first treated. Factors known to increase your risk of cancer include:

Getting older is the most significant overall risk factor for cancer. As your age increases, your possibility of having it increases. Look at the statistics – there are fewer than 25 cases of cancer per 100,000 people for age groups under 20, about 350 cases per 100,000 people aged 45-49, and more than 1,000 cases per 100,000 people 60 and older.

Habits and Lifestyle
Certain lifestyle choices increase your risk of cancer. Smoking, drinking more than one drink a day for women and up to two drinks a day for men, excessive exposure to the sun or frequent blistering sunburns, being obese and having unsafe sex can contribute to cancer. You can change these habits to lower your cancer risk — though some habits are easier to change than others.

Family History
Only a small portion of cancers are due to an inherited condition. If cancer is common in your family, it’s possible that mutations are being passed from one generation to the next. You might be a candidate for genetic testing to see whether you have inherited mutations that might increase your risk of certain cancers. Remember that having an inherited genetic mutation doesn’t necessarily mean you’ll get cancer.

Health Conditions
There are several health conditions that can increase your chances of getting cancer. Let’s take a look at them:

  • Obesity – excess body fat can lead to colorectal, post-menopausal breast, uterine, esophageal, kidney, and pancreatic cancers
  • Ulcerative colitis – the inflammation and cell replacement associated with this condition can become a mutation that leads to cancer
  • Viral infections – all of these are linked with certain types of cancer: human papillomavirus (HPV), hepatitis, epstein-barr virus, Kaposi’s sarcoma-associated herpes virus, human t-cell leukemia virus, Merkel cell polyomavirus
  • Inherited gene mutations – gene changes passed down to you from your parents can make it more likely that you get certain types of cancer
  • Hormonal imbalances – excess estrogen can cause cancer of the uterus (endometrial cancer)

The environment around you may contain harmful chemicals that can increase your cancer risk. Even if you don’t smoke, you might inhale secondhand smoke if you go where people smoke or if you live with someone who smokes. Chemicals in your home or workplace (such as asbestos and benzene) also are associated with an increased risk of cancer.

Although risk factors often influence cancer development, most do not directly cause cancer. Some people with several risk factors never develop cancer while others with no known risk factors do. Knowing your risk factors and discussing them with your doctor may help you make more informed lifestyle and healthcare choices.

How To Slow the Spread of Cancer

There are many types of cancer treatment, and the types of treatment you receive will depend on the type of cancer with which you have been diagnosed and how advanced it is. Here are some types of cancer treatment you might receive that can slow the spread:

  • Biomarker Testing for Cancer Treatment: Biomarker testing is a way to look for genes, proteins and other substances (called biomarkers or tumor markers) that can provide cancer information. Biomarker testing can help you and your doctor choose a cancer treatment.
  • Chemotherapy: Chemotherapy is a cancer treatment that uses drugs to kill cancer cells.
  • Hormone Therapy: Hormone therapy is a treatment that slows or stops the growth of breast and prostate cancers that use hormones to grow healthy cells.
  • Hyperthermia Treatment: Hyperthermia is a treatment in which body tissue is heated to as high 113 ℉ to help damage and kill cancer cells with little or no harm to normal tissue.
  • Immunotherapy: Immunotherapy is a cancer treatment that helps your immune system fight cancer.
  • Photodynamic Therapy: Photodynamic therapy uses a drug activated by light to kill cancer and other abnormal cells.
  • Radiation Therapy: Radiation therapy is a type of cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors.
  • Stem Cell Transplant: Stem cell transplants are procedures that restore stem cells that grow into blood cells in people who have had theirs destroyed by high doses of chemotherapy or radiation therapy.
  • Surgery: When used to treat cancer, surgery is a procedure in which a surgeon removes cancerous tumors from your body.
  • Targeted Therapy: Targeted therapy is a type of cancer treatment that targets the changes in cancer cells that help them grow, divide and spread.

Visit Yosemite Pathology

Since 1948, our laboratory has provided superior and comprehensive diagnostics in anatomic pathology in the Western United States. The broad range of specialties practiced by our dedicated pathologists in the cancer field includes those of the breast, skin, thyroid, gastrointestinal system, among others. Visit us today for cancer screenings, preventative care and treatment.

Sarah Carpenter is a freelance writer whose portfolio spans the industries of healthcare, higher education and entertainment. Find out more at her website.

National Cancer Institute – Metastatic Cancer: When Cancer Spreads
Mayo Clinic – Cancer
American Society of Clinical Oncology – Breast Cancer- Metastatic: Risk Factors
National Cancer Institute – Age and Cancer Risk
National Cancer Institute – Types of Cancer Treatment