Cancer Pain — Causes, WHO Analgesic Ladder & Management Guide — Symptoms, Causes & Treatment | MyMedicPlus

Cancer pain is pain caused by cancer or its treatment, affecting 50-80% of cancer patients and 70% of those with advanced disease. It is one of the most feared consequences of cancer but is often undertreated due to opiophobia, inadequate assessment, and poor palliative care access. Cancer pain can be nociceptive (from tissue damage — somatic or visceral), neuropathic (from nerve injury by tumour or treatment), or mixed. The WHO analgesic ladder, developed in 1986, provides a framework for stepwise pain management and, when properly applied, adequately controls 80-90% of cancer pain. Despite effective treatments being available, cancer pain remains globally undertreated — the WHO estimates that 80% of people with cancer pain in low- and middle-income countries cannot access adequate opioid analgesia due to regulatory barriers, poor opioid availability, and insufficient palliative care infrastructure. This represents a profound global health inequity. The goal of cancer pain management is not merely pain reduction, but enabling the patient to maintain functional capacity and quality of life throughout the cancer journey and end of life.

Tumour-related pain: bone metastases (most common — causes severe pain from periosteal stretching, fractures), nerve compression or invasion (neuropathic pain), visceral distension (from hepatomegaly, bowel obstruction, ascites), skin or soft tissue invasion, and raised intracranial pressure from brain metastases. Treatment-related pain: chemotherapy-induced peripheral neuropathy (CIPN — tingling/burning in hands and feet from taxanes, platinums, vinca alkaloids), post-surgical pain, radiation mucositis, post-mastectomy pain syndrome, and steroid withdrawal. Concurrent conditions (arthritis, infection) can worsen pain in cancer patients. Cancer-induced bone disease — osteolytic lesions causing trabecular destruction — triggers local prostaglandin release, nerve growth factor upregulation, and direct nerve fibre sensitisation, creating a uniquely complex pain state with both inflammatory nociceptive and neuropathic components. Radiation-induced brachial and lumbosacral plexopathies cause chronic neuropathic pain appearing months to years after treatment. Opioid-induced hyperalgesia (paradoxical increase in pain sensitivity with increasing opioid doses) is an important treatment challenge.

Cancer pain varies widely in character depending on the cause: somatic pain is well-localised and aching (bone metastases); visceral pain is diffuse, cramping, or pressure-like (liver capsule distension, bowel obstruction); neuropathic pain is burning, electric shock-like, stabbing, or associated with allodynia (pain from non-painful stimuli) and hyperalgesia. Pain is assessed using numeric rating scales (0-10), descriptive scales, or multidimensional tools (Brief Pain Inventory). Breakthrough pain — transient severe pain superimposed on controlled background pain — affects 50-90% of cancer pain patients and requires rapid-onset analgesics. Total pain concept (Cicely Saunders) recognises that cancer pain has physical, psychological, social, and spiritual dimensions — all of which must be assessed and addressed for adequate relief. Deafferentation pain (from nerve destruction by tumour) causes spontaneous burning, shooting pain and allodynia that is often refractory to standard analgesics and requires specialist neuropathic pain treatment.

Comprehensive pain assessment includes: pain location and radiation; character (aching, burning, sharp, stabbing); intensity (numeric rating scale); temporal pattern (constant, intermittent, breakthrough); aggravating and relieving factors; impact on function and sleep; and previous analgesic history and response. Examination identifies the pain source and neurology. Imaging (CT, MRI, bone scan, PET) identifies the underlying cause (bone metastases, nerve compression, visceral disease). Neurological examination guides neuropathic pain diagnosis. The Edmonton Symptom Assessment Scale (ESAS) and palliative care assessment tools provide comprehensive symptom evaluation. The Brief Pain Inventory (BPI) quantifies pain intensity and functional interference and is the most widely validated tool for cancer pain assessment in clinical trials and practice. Palliative care assessment includes not only pain scores but also functional status (ECOG/Karnofsky scale), nutritional status, quality of life measures, and carer burden assessment to guide comprehensive symptom management planning.

WHO Analgesic Ladder: Step 1 — paracetamol and/or NSAIDs (ibuprofen, naproxen, diclofenac) for mild pain; Step 2 — weak opioids (codeine, tramadol, dihydrocodeine) added for moderate pain not controlled by Step 1; Step 3 — strong opioids (oral morphine, oxycodone, hydromorphone; transdermal fentanyl or buprenorphine patches for stable pain; subcutaneous syringe driver for terminal phase) for severe pain. Adjuvant analgesics: amitriptyline, gabapentin, pregabalin, duloxetine for neuropathic pain; bisphosphonates/denosumab for bone pain; corticosteroids for nerve compression/raised ICP; ketamine for complex refractory pain. Interventional: nerve blocks (coeliac plexus block for pancreatic cancer pain), intrathecal drug delivery, epidural analgesia, palliative radiotherapy (highly effective for bone metastases, providing relief in 60-70%). Palliative care team ensures holistic support. Ketamine infusions (sub-anaesthetic doses, 0.1-0.5 mg/kg/hour) provide opioid-sparing analgesia in complex cancer pain, particularly for neuropathic and opioid-resistant pain. Radioisotope therapy (radium-223 for bone-metastatic castrate-resistant prostate cancer) reduces bone pain and improves survival. Methadone, due to its dual mechanism (opioid agonist and NMDA antagonist), is effective for complex neuropathic cancer pain.

Uncontrolled cancer pain causes profound suffering, severe functional impairment, sleep deprivation, depression, anxiety, social isolation, and suicidal ideation. It reduces adherence to cancer treatment (patients may refuse further chemotherapy due to pain/side effects). Inadequate opioid prescribing and access to palliative care medicines remains a global health crisis — the WHO estimates 80% of people worldwide who need opioid pain medicines cannot access them. Unnecessary suffering at end of life is preventable with adequate palliative care resources and training. Pain crisis at home can lead to emergency hospital admissions and reduced quality of life in the final months.

Take analgesics regularly ('by the clock') rather than waiting for severe pain — regular dosing maintains constant blood levels and prevents pain peaks. Do not fear opioids — when used for cancer pain under medical supervision, addiction is rare (under 1%); dependence is different from addiction, and dependence is manageable. Breakthrough doses: have fast-acting opioid available for breakthrough pain episodes — typically 1/6 of the 24-hour regular dose. Complementary approaches for pain management: relaxation techniques, mindfulness, TENS (transcutaneous electrical nerve stimulation), heat/cold therapy, physiotherapy, and acupuncture — used alongside, not instead of, medical analgesics. Early palliative care referral improves not just symptom control but also survival.

If you have cancer and your pain is not adequately controlled — pain scoring above 4 out of 10, or pain that is preventing sleep, daily activities, or adherence to cancer treatment — contact your oncologist or palliative care team promptly; do not wait until your next scheduled appointment. Most hospitals have a palliative care or acute oncology advice line available 24 hours a day. Go to A&E or call 999 immediately for: sudden severe pain crisis; breathlessness with chest pain; new lower limb weakness, numbness, or loss of bladder or bowel control (possible spinal cord compression — an oncological emergency requiring urgent MRI and dexamethasone); or signs of opioid toxicity (extreme drowsiness, very slow or shallow breathing, pinpoint pupils — give naloxone if available, call 999). Early referral to specialist palliative care — ideally at diagnosis of advanced or metastatic cancer — improves pain control, quality of life, and should not be delayed until the terminal phase.