Why Does Cancer Relapse?
July 7, 2026Core Framework & Diagram Why Does Cancer Metastasize?
July 7, 2026
Why Does Cancer Metastasize?
Cancer's real lethality isn't growing at its origin — it's that it goes elsewhere
By the Editors 1-min read
Why do breast cancer patients ultimately die more often from lung failure or bone pain than from breast itself? Why, after most cancer surgeries are done 'cleanly,' are patients primarily worried not about the original tumor but where it may have gone?
Because cancer's true lethality is metastasis — the process by which cancer cells leave the primary tumor, travel through blood or lymphatic circulation, migrate to distant organs, and establish new tumors there. Approximately ninety percent of global cancer deaths come from metastatic disease, not the primary tumor.
Metastasis isn't random — it's a complex process requiring cancer cells to overcome dozens of biological checkpoints, with the immune system setting up barriers at every checkpoint. Understanding why some cancer cells can break through these barriers is the core of understanding cancer metastasis prevention and treatment.
KEY TAKEAWAYS
01
Metastasis is an extremely inefficient but once successful extremely lethal process: among millions of CTCs entering blood, only approximately 0.01% form clinical metastatic lesions; but ninety percent of cancer deaths come from metastasis rather than the primary tumor.
02
EMT is metastasis's first step, granting migratory capacity while simultaneously via shared transcription factors (SNAIL etc.) synchronously enhancing immune evasion capacity — the most metastatically capable cancer cells are simultaneously hardest for the immune system to recognize.
03
CTCs face powerful NK cell elimination in blood (average lifespan ~2.5 hours); using a 'platelet coat' to evade NK cells is the primary protection strategy. Low-dose aspirin blocking platelet-CTC binding correlates with reduced metastasis risk in multiple cancers — mechanistically sound but not yet standard recommendation.
04
The Pre-metastatic Niche (PMN) discovery means: before cancer cells arrive at distant organs, the primary tumor has already 'remodeled' the target organ through exosomes and distant signals — anti-metastasis prevention strategies targeting PMN formation are an important research frontier.
05
Organ-specific metastasis has clear molecular mechanisms providing precise molecular targets for anti-metastasis treatment: breast cancer → bone CXCR4-CXCL12 axis; colorectal cancer → liver physical portal vein drainage; bisphosphonates and RANKL inhibitors break bone lysis positive feedback.
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