Cancer Pain

Definition

Cancer pain is a complex, multidimensional symptom resulting from tumor growth, treatment, or associated complications. It can be nociceptive, neuropathic, or mixed in origin and significantly affects quality of life.

Epidemiology

• Affects up to 70–80% of patients with advanced cancer
• Pain prevalence higher in metastatic and terminal-stage disease
• Commonly under-treated globally, particularly in low-resource settings
• Pain can be a presenting symptom in certain cancers (e.g., pancreatic, bone, head and neck)
• Significant psychosocial burden on patients and caregivers

Etiology

• Direct tumor invasion causing tissue, bone, nerve, or organ compression
• Treatment-related causes: surgery, chemotherapy, radiotherapy, immunotherapy
• Procedural pain: biopsies, catheter placement, interventions
• Inflammatory mediators released by tumor cells
• Neuropathic mechanisms: nerve injury or infiltration

Pathophysiology

• Nociceptive pain: activation of somatic or visceral nociceptors by tumor or inflammation
• Neuropathic pain: injury or compression of peripheral or central nerves
• Mixed pain: combination of nociceptive and neuropathic mechanisms
• Central sensitization: amplification of pain signaling in the spinal cord and brain
• Psychosocial factors: anxiety, depression, and fear can exacerbate pain perception