Metastatic cancer: What happens when cancer spreads?

If you’ve recently received a cancer diagnosis, you may have heard the word “metastasis” or been asked by someone if your cancer has metastasized. But, what is metastasis? What does it mean for your cancer treatment? And is it curable?

We got details on metastasis from Jeffrey Gershenwald, M.D., a surgical oncologist who specializes in the care of patients with  melanoma and has contributed to the world’s leading guides on melanoma staging.

What is cancer metastasis?  

Cancer occurs when an abnormal cell inside the human body duplicates. Sometimes these cells form a mass called a tumor. When those cells spread from the original site they started in and spread to other places in the body, they’re called metastases. In other words, when cancer has metastasized, we mean it has spread. 

We classify cancer by where it starts, no matter where it spreads to. Breast cancer is cancer that started in the breast, and bladder cancer is cancer that started in the bladder. When bladder cancer spreads to a region like the liver, for example, the patient does not have liver cancer and bladder cancer. We consider the bladder cancer to be what’s called the primary cancer, and the liver to be the site of the metastases.

What stage is metastatic cancer?

It differs depending on the cancer type, but in most cases, cancer that has spread to distant organs is stage IV cancer. If cancer has spread to nearby lymph nodes or other close tissues, it’s generally stage III.

Is metastatic cancer curable?

Whether or not a cancer can be truly cured is not an easy question to answer. It depends on many different factors, and there’s not a one-size-fits-all response for metastatic cancer as a whole or for specific types of metastatic cancer. It’s true that cancer is easier to treat when it’s limited to just one mass and hasn’t spread, and it used to be very difficult to treat metastatic cancer. But we’ve made incredible advances in cancer treatment with new treatments and are finding new ways to treat metastatic cancer through clinical trials. As a result, we’re now able to treat metastatic disease so patients live longer and/or more comfortable lives. For example, stage IV melanoma used to be considered impossible to treat for most cancers, but thanks to immunotherapy and some other treatments, these patients are seeing no evidence of disease for several years.

How does cancer spread or metastasize?

There are a few ways cancer cells may spread. They may move directly into the nearby areas, or they might travel through the blood stream or the lymph node system to other parts of the body.

Where does cancer most commonly metastasize, or spread, to?

When cancer spreads to a nearby organ or body part, it is generally considered a “regional metastasis.” If cancer spreads far away from its original site, it’s considered a “distant metastasis.”

Researchers have been studying cancer and the way it spreads for decades. We’ve learned which cancers are more likely to have regional metastases and which ones are more likely to have distant metastases. For example, breast cancer is more likely to spread to the nearby lymph nodes – a regional metastasis. Melanoma, lung, breast and kidney cancer all carry a risk of spreading to the brain – a distant metastasis. In fact, an estimated 150,000 to 200,000 people are diagnosed with brain metastasis each year, compared to about 17,000 diagnoses for primary brain tumors.

Common sites where cancer spreads:

• Bladder cancer: bone, liver, lung
• Breast cancer: Bone, brain, liver, lung
• Colorectal cancer: Liver, lung
• Lung cancer: Adrenal gland, bone, brain, liver, other lung
• Melanoma cancer: Bone, brain, liver, lung, skin
• Thyroid cancer: Bone, liver, lung

Are there any symptoms of metastasis that patients should look for?

Symptoms of cancer metastasis depend on where the cancer has spread.

If a cancer spreads to the brain, a patient may experience dizziness, blurred vision, weakness or headaches.

If the cancer spreads to parts of the digestive system, patients may experience changes in bowel habits.

If you’ve recently been diagnosed with a localized cancer – one that hasn’t spread – your care team can tell you if your cancer is likely to spread and what symptoms to look for.

It’s important to share any symptoms you experience with your care team so you can catch metastases early. Early detection is key to successful cancer treatment. 

How is metastatic cancer diagnosed?

Often the care team’s first step after determining a cancer diagnosis it to determine if that cancer has spread and where it has spread to. This process is called “staging.” Sometimes staging is conducted through screenings and diagnostic imaging procedures, like MRIs, CT scans or PET scans. In these tests, the areas the cancer have spread to will “light up” or become apparent. Staging may also be conducted through biopsies, like blood tests and surgeries that show where cancer has spread. How many parts of the body the cancer has spread to determines the stage of the cancer. This will be different for each cancer type, and not all cancers require formal staging, but typically, the higher the stage, the more places the cancer has spread.

How is metastatic cancer treated?  

When cancer has spread, it typically is treated differently and more aggressively. Fortunately, we’ve made many advances in treating metastatic cancer. If your cancer has spread, it’s less likely that surgery will play a large role in your treatment. Instead, doctors will rely on treatments like chemotherapy, radiation, proton therapy or immunotherapy to treat metastatic cancer.

What advice do you have for patients with a new metastatic cancer diagnosis?

Treating metastatic cancer is complex. Find a multidisciplinary care team that has experience treating your specific cancer type. They’re more likely to be familiar with the latest in clinical trials and new treatments. New targeted therapies are improving and bringing hope to our patients. Finding the right care team with the right treatment can help cancer patients get more time and a better quality of life.

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