How Cancer Harms the Body: Local Invasion, Systemic Effects, and Metastasis

Local/Regional Effects

• Mass Effect: Compression/obstruction of organs, ducts, vessels, nerves (e.g., biliary obstruction, SVC syndrome, cord compression).
• Invasion: Destruction of normal tissue architecture and function.
• Ulceration/Bleeding: Mucosal tumors (GI, GU, aerodigestive).

Systemic/Paraneoplastic Effects

• Cytokine-Mediated: Cachexia (TNF-α, IL-1, IL-6 → anorexia, muscle/fat wasting), fever, anemia of chronic disease.
• Hormonal: Ectopic hormone production (e.g., PTHrP → hypercalcemia; ACTH → Cushing's; ADH → SIADH).
• Autoimmune: Paraneoplastic syndromes (anti-Hu, Yo, Ri, Ma2 → encephalitis, cerebellar degeneration, neuropathy).
• Coagulopathy: Trousseau's syndrome (mucin-secreting adenocarcinomas → migratory thrombophlebitis).

Metastatic Spread

• Lymphatic → nodal → distant nodes.
• Hematogenous → liver, lung, bone, brain (organ-specific tropism).
• Transcoelomic → peritoneal carcinomatosis.

Treatment Toxicity

Chemotherapy, radiation, immunotherapy, surgery add iatrogenic morbidity (myelosuppression, neuropathy, cardiotoxicity, second cancers).