Oncology 101: The Fundamentals of Cancer • Topic 4 of 6
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Oncology 101: The Fundamentals of Cancer

A comprehensive overview of the basic principles of oncology, from the biology of cancer to treatment modalities.

Understanding Cancer Metastasis

The process that makes cancer truly dangerous

Metastasis is the process by which cancer cells spread from their original location to other parts of the body. It is responsible for approximately 90% of cancer-related deaths, making it the most critical aspect of cancer biology to understand. This module will take you through the complex journey of metastatic progression, from the initial steps of local invasion to the establishment of distant colonies.

A History of Metastasis Theory

1829 - Joseph Recamier

Coined the term "metastasis"

First to describe the spread of cancer from one part of the body to another.

1858 - Rudolf Virchow

Mechanical theory

Proposed that metastasis was mechanical: cancer cells simply broke off and got stuck in distant blood vessels.

1889 - Stephen Paget

Seed and Soil hypothesis

Introduced the "Seed and Soil" hypothesis, arguing that cancer cells ("seeds") can only grow in specific, hospitable organs ("congenial soil").

1928 - James Ewing

Anatomical route theory

Challenged Paget, suggesting metastasis was determined purely by the anatomical routes of blood and lymph flow.

1970s - Josh Fidler

Multi-step process synthesis

Synthesized all previous theories, demonstrating that metastasis is a multi-step process involving specific cancer cell capabilities and their interaction with the microenvironment.

The 8 Steps of the Metastatic Cascade

1
Primary Tumor Growth

Uncontrolled proliferation forms a tumor mass.

Cancer cells acquire the ability to grow and divide uncontrollably, forming the initial tumor.
2
Angiogenesis

Tumor induces new, leaky blood vessels.

The tumor secretes factors like VEGF to stimulate blood vessel formation, providing nutrients and oxygen.
3
EMT

Cells become mobile and invasive.

Epithelial-Mesenchymal Transition: cells lose adhesion and gain migratory properties.
4
Invasion

Mobile cells break through local tissue barriers.

Cancer cells invade surrounding tissue by breaking down the extracellular matrix.
5
Intravasation

Cancer cells enter blood or lymphatic vessels.

Invasive cancer cells breach vascular walls to enter the circulatory system.
6
Circulation & Survival

Cells survive the hostile circulatory environment.

Most circulating tumor cells die, but some survive mechanical stress and immune attacks.
7
Extravasation

Surviving cells exit circulation at distant sites.

Circulating tumor cells adhere to vessel walls and extravasate into target tissues.
8
Colonization

Establishment of secondary tumors.

Extravasated cells adapt to the new microenvironment and form metastatic colonies.

Why Metastasis is So Deadly

  • • Survival rates plummet: As shown in the chart, metastatic cancer has dramatically lower survival rates
  • • Treatment complexity: Metastatic disease is much harder to treat than localized cancer
  • • Multiple organ involvement: Cancer can spread to vital organs like liver, lungs, and brain
  • • Therapeutic resistance: Metastatic cells often develop resistance to treatments

Modern Understanding

  • • Multi-step process: Metastasis requires multiple molecular changes
  • • Seed and soil: Both cancer cell properties and organ environment matter
  • • Dormancy: Cancer cells can remain dormant for years before growing
  • • Therapeutic targets: Each step offers potential intervention points