Oncology 101: The Fundamentals of Cancer
A comprehensive overview of the basic principles of oncology, from the biology of cancer to treatment modalities.
Part 5: Cancer Staging & Ecology
Understanding how cancer spreads and the environments it creates
The TNM Staging System
A universal system to classify the extent of cancer spread, guiding prognosis and treatment.
T
Tumor
Describes the size and extent of the primary tumor. A larger number (e.g., T4 vs. T1) indicates a larger or more invasive tumor.
N
Node
Indicates if the cancer has spread to nearby lymph nodes. N0 means no spread; N1, N2, etc., indicate increasing involvement.
M
Metastasis
Indicates if the cancer has metastasized to distant parts of the body. M0 means no metastasis; M1 means it has spread.
Example: A patient with a T1 N0 M0 stage has a small, localized tumor with a good prognosis. A T4 N2 M1 stage indicates a large, invasive tumor that has spread to lymph nodes and distant organs, representing a much more serious condition.
Cancer Ecology: The Seed, Soil, and Swamp
This paradigm views cancer not just as a disease of cells, but as a complex ecosystem.
Seed and Soil
Proposed by Stephen Paget in 1889, this hypothesis states that metastatic cancer cells (the "seeds") can only grow in specific, hospitable distant organs (the "soil").
- •Explains why certain cancers tend to metastasize to specific sites
- •Prostate cancer commonly spreads to bone
- •Breast cancer often metastasizes to liver, lung, bone, and brain
- •Colon cancer frequently spreads to liver
The Cancer Swamp
The primary tumor creates its own hostile ecosystem—hypoxic, acidic, and nutrient-poor.
- •Harsh environment drives evolution of aggressive cancer cells
- •Hypoxic (low oxygen) conditions
- •Acidic pH from altered metabolism
- •Nutrient depletion from rapid growth
- •Pressures cells to escape (metastasize) in search of better environment
Oligometastasis: A State of Limited Metastatic Disease
A theory that a less aggressive "laid back" form of metastasis exists, where patients have only a few metastatic lesions and may still be curable.
Oligometastasis (Limited)
- •Primary tumor is less harsh
- •Fewer, less aggressive CTCs are shed
- •Distant organs are less hospitable "soil"
- •Result: Few, treatable metastatic lesions
Widespread Metastasis (Aggressive)
- •Primary tumor is a harsh "cancer swamp"
- •Many, aggressive CTCs are shed
- •Distant organs are fertile "soil"
- •Result: Numerous, difficult-to-treat lesions