How can we overcome cancer pain?

Cancer is a major disease affecting Australians, and represents one of the major underlying causes of death.1 The term cancer includes a variety of different diseases (such as malignant solid tumours, sarcomas, Hodgkin’s lymphoma and leukaemias) characterised by disordered cell growth and reproduction. It is estimated that cancer accounts for approximately 28% of all Australian deaths each year. Furthermore, cancer related illnesses create significant morbidity, disability and account for a considerable proportion of public health expenditure in Australia.1 Lung cancer, colorectal cancer and breast cancer are the leading specific types of cancer contributing to Australia’s total burden of disease. Chronic pain is a frequent complaint of oncology patients and an important aspect of palliative care management. This article focuses on the incidence and clinical features of cancer pain and suggests strategies to address this issue.

Prevalence

In 2004-05, approximately 2% of the population (about 390,000 people) reported that they currently had a medically diagnosed neoplasm. Of these people, 87% reported that they had a malignant neoplasm (cancer) and 14% reported that they had a benign neoplasm or neoplasm of an uncertain nature.¹

Incidence

Data from cancer registries show that prostate cancer is the most common registered cancer in males (11,191 new cases diagnosed in 2001), followed by colorectal cancers, lung carcinoma and melanoma. In females breast cancer is the most common newly diagnosed registrable cancer (11,791 new cases diagnosed in 2001), followed by colorectal carcinoma, colon cancer and melanoma.¹

Cancer pain

Chronic pain is a well recognised complication of various forms of cancer and creates substantial burdens for patients and carers. Pain may include nociceptive, neuropathic and mixed forms, the latter two creating significant challenges in cancer pain management.² Despite its prevalence, little data is currently available about the extent of the pain suffered by cancer patients. A population-based study was recently conducted in the Netherlands to obtain reliable information about the prevalence and severity of pain in cancer patients (all phases) and clinical predictors of pain.³ A representative sample of cancer patients were recruited from a cancer registry. Pain was assessed by the Brief Pain Inventory (BPI) and adequacy of pain treatment by the Pain Management Index (PMI). This study found that 55% of the 1,429 respondents had experienced pain in the past week and 44% of these patients reported moderate to severe pain (BPI score 4). Pain management treatment was inadequate in 42% of cancer pain patients. Positive predictors of pain were lower education level, more advanced disease and haematological (excluding non-Hodgkin lymphoma), gastro-intestinal, lung, or breast malignancies.³

Neuropathic cancer pain

Neuropathic pain is broadly defined as pain caused by lesions or dysfunction of the peripheral or central nervous systems.⁴ In cancer, neuropathic pain is predominantly caused by tumour infiltration or compression of the peripheral or central nervous system.⁵ Cancer treatments including radiotherapy, surgery and chemotherapeutic agents may also contribute to painful neuropathies.⁵ In addition, debilitated cancer patients may be prone to development of diseases such as herpes zoster and subsequent post-herpetic neuralgias.⁶

Patients with cancer may experience neuropathic pain as a continuous burning, shooting or electric sensations (continuous dysesthesias) or sudden episodes of sharp, stabbing, shooting, knife-like pain (lancinating or paroxysmal pain).⁵ Neuropathic pain may be debilitating, distressing and generally difficult to treat. Neuropathic pain syndromes are therefore one of the major problems of cancer pain treatment. Recognition of appropriate pain syndromes is essential for the adequate management of cancer pain. In a recent survey of 593 cancer patients seeking pain relief, 32 presented with neuropathic and 181 had mixed nociceptive and neuropathic pain syndromes.²

Managing neuropathic cancer pain

The effectiveness of opioids in the management of intractable pain such as neuropathic pain is controversial.² Adjuvant analgesics play an essential role in the management of neuropathic pain.⁵ However, antidepressants (including tricyclics) may be associated with significant side effects that limit their use.⁴

International and Australian treatment algorithms in primary care suggest the gabapentinoids such as gabapentin (Neurontin) and its structural analogue pregabalin (Lyrica) have proven evidence-based efficacy in the treatment of neuropathic pain and lack serious adverse effects.⁷ The theory behind their efficacy is centred on the reduction of neuronal hyperexcitability.⁴ Pregabalin would appear to be superior to gabapentin because of its linear pharmacokinetics, linear dose response, faster onset of pain relief and reduction in sleep disturbance (within the first week of therapy), as well as having an effective starting dose of 75mg twice daily.⁷ Pregabalin may therefore be an effective first line agent for the management of neuropathic pain,^8,9 however, its specific use in cancer pain settings is still emerging.

Successful treatment of neuropathic pain in cancer patients requires a multidisciplinary approach.⁴ Adjuvant analgesics should always be used in combination with an appropriate supportive therapeutic relationship and non- pharmacological treatments.

Conclusions

Cancer pain management is an ongoing challenge in palliative and primary care settings. Neuropathic forms of pain are common and frequently require additional adjuvant analgesic therapies.^2,5 Research into neuropathic pain treatments is currently ongoing; however novel agents such as anticonvulsant treatments have recently shown promise (particularly in the management of diabetic neuropathies and post-herpetic neuralgias). Medical professionals are encouraged to remain up to date with emerging therapies and ongoing research into the management of cancer pain.

References

Australian Bureau of Statistics. Cancer in Australia: A Snapshot, 2004-05 issue 4822.0.55.001; available [online] at URL: http://www.abs.gov.au/ausstats/abs@.nsf/mf/4822.0.55.001
Grond S, et al. Assessment and treatment of neuropathic cancer pain following WHO guidelines. Pain 1999; 79(1): 15-20; available [online] at URL: http://www.sciencedirect.com/
van den Beuken-van Everdingen MH, et al. High prevalence of pain in patients with cancer in a large population-based study in the Netherlands. Pain 2007; available [on-line] at URL: http://www.pain-initiative.com/
Helme R. Drug treatment of neuropathic pain. Australian Prescriber 2006; 29(3): 72-5; available [online] at URL: http://www.australianprescriber.com/upload/pdf/articles/803.pdf
World Health Organisation document: The essential adjuvant analgesics for neuropathic pain; available [on-line] at URL: http://www.whocancerpain.wisc.edu/eng/15_2/essential.html
Insinga RP, Itzler RF, Pellissier JM. Acute/subacute herpes zoster: healthcare resource utilisation and costs in a group of US health plans. Pharmacoeconomics. 2007; 25(2): 155-69; available [on-line] at URL: http://www.ncbi.nlm.nih.gov/
LYRICA^(R) Product Information; available [on-line] at URL: www.Lyrica.com.au
Finnerup NB et al. Algorithm for neuropathic pain treatment: an evidence based proposal. Pain. 2005; 118: 289-305; available [online] at URL: http://www.ncbi.nlm.nih.gov/
SPHERE. Positive management of persistent pain – neuropathic pain treatment algorithm and diagnostic questionnaire; available [online] at URL: http:/www.spheregp.com.au/index.htm