Metastasis

• Metastasis is the spread of cancer cells from the primary tumor to distant parts of the body.
• The process involves several steps, including invasion, intravasation, circulation, extravasation, and colonization.
• Metastatic cancer can present with varied symptoms depending on the secondary tumor sites.
• Treatment options aim to control disease progression, alleviate symptoms, and improve quality of life.

What is Metastasis?

Metastasis refers to the process by which cancer cells detach from a primary tumor and travel through the bloodstream or lymphatic system to form new tumors in other organs or tissues. This spread is a hallmark of advanced cancer and is responsible for the majority of cancer-related deaths. When cancer metastasizes, the secondary tumors are made of the same type of cancer cells as the original tumor, even if they are located in a different part of the body. For example, breast cancer that spreads to the lungs is still considered metastatic breast cancer, not lung cancer. The ability of cancer cells to metastasize is a complex biological phenomenon involving multiple genetic and cellular changes. These changes allow cancer cells to acquire characteristics that enable them to invade surrounding tissues, survive in new environments, and proliferate to form secondary tumors. The presence of metastasis often indicates a more advanced stage of cancer.

The Process of Cancer Metastasis

Understanding how cancer metastasizes involves recognizing a multi-step cascade, often referred to as the metastatic cascade. This intricate process begins when cancer cells at the primary tumor site acquire the ability to invade surrounding healthy tissue. They then penetrate the walls of nearby blood vessels or lymphatic vessels, a process known as intravasation. Once inside these circulatory systems, the cancer cells travel through the body, often encountering immune cells and other challenges. During circulation, many cancer cells perish, but some manage to survive by forming clumps or by evading immune detection. These surviving cells eventually adhere to the walls of blood vessels or lymphatic vessels in distant organs and exit the circulation, a step called extravasation. Finally, these disseminated cancer cells establish themselves in the new tissue, proliferate, and form a new tumor, a process known as colonization. The specific organs where cancer cells metastasize often depend on the type of primary cancer and the unique characteristics of the cancer cells themselves. Common sites for metastasis include the bones, lungs, liver, and brain.

Recognizing and Managing Metastatic Cancer

The symptoms of metastatic cancer can vary widely depending on the location of the secondary tumors. For instance, cancer that has spread to the bones might cause pain, fractures, or high calcium levels. Lung metastases can lead to shortness of breath, cough, or chest pain, while liver metastases might cause jaundice, abdominal pain, or fatigue. Brain metastases can result in headaches, seizures, or neurological deficits. It is crucial for individuals with a history of cancer to be aware of new or worsening symptoms and report them to their healthcare provider promptly.

• Bones: Pain, fractures, numbness or weakness if near the spinal cord.
• Lungs: Persistent cough, shortness of breath, chest pain.
• Liver: Abdominal pain, jaundice (yellow skin/eyes), nausea, loss of appetite.
• Brain: Headaches, seizures, dizziness, changes in vision or speech.

Metastasis treatment options are typically aimed at controlling the disease, alleviating symptoms, and improving the patient’s quality of life, as metastatic cancer is often not curable. Treatment strategies are highly individualized and depend on the type of primary cancer, the location and extent of metastasis, previous treatments, and the patient’s overall health. Common approaches include systemic therapies such as chemotherapy, targeted therapy, immunotherapy, and hormone therapy, which work throughout the body to kill cancer cells or stop their growth. Localized treatments like radiation therapy or surgery may be used to manage specific metastatic sites, reduce pain, or prevent complications. Clinical trials also offer access to innovative new treatments. Patients should always discuss all potential treatment options with their oncology team to determine the most appropriate course of action.