Pain following cancer treatment
In addition to fatigue, pain is the most frequent persistent symptom in cancer survivors. Clear guidelines for both the diagnosis and treatment of pain in cancer survivors are lacking.
Classification of pain is important as it may facilitate more specific targeting of treatment, pharmalogical and non-pharmalogical. For example, pain education is an effective but underused strategy for treating cancer pain. Physiotherapy for cancer pain, patient-centered and founded on a mechanisms-based classification of pain, has previously been shown to yield positive findings.
Recently, a clinical method for classifying any pain as either predominant central sensitization pain, neuropathic or nociceptive pain was developed, based on a large body of research evidence and international expert opinion.
The classification of pain following cancer treatment entails two steps: (1) examining the presence of neuropathic pain; and (2) using an algorithm for differentiating predominant nociceptive or central sensitization pain.
Step 1 builds on the established criteria for neuropathic pain diagnosis (nervous system lesion identifiable, specific pain and hyperalgesia distribution and presence of sensory abnormalities), while step 2 applies a recently developed clinical method (see illustration) for classifying any pain as either predominant central sensitization pain, neuropathic or nociceptive pain to the cancer survivor population.
This study presents an overview of nociceptive, neuropathic and central sensitization pain following cancer treatment.
Nociceptive pain is defined as pain attributable to the activation of the peripheral receptive terminals of primary afferent neurons in response to noxious chemical, mechanical or thermal stimuli, or as pain arising from actual or threat of damage to non-neural tissue and is due to the activation of nociceptors.
Neuropathic pain is defined as pain caused by a primary lesion or disease of the somatosensory nervous system.
Central sensitization implies increased neuronal response to stimuli in the central nervous system (i.e. central hyperexcitability) and reduced pain modulation. Often, "illogical" pain patterns are seen, outside the area of nociception. Overall sensory hypersensitivity in cancer survivors can be tested using quantitative sensory testing (QST), or the Central Sensitization Inventory (CSI).
The study, which included a team of 15 authors from 13 different centers, 4 countries and 2 continents, applied this classification algorithm to the cancer survivor population.
To assess if pain is disproportionate to the extent of injury, knowledge of common sources of nociception in cancer survivors is required.
EMG, CT and MRI may be used to differentiate between nociceptive and neuropathic pain.
Plus, a multidimensional assessment of pain is warranted. This can be done using the Short-Form McGill Pain Questionnaire-2, tested in the cancer population.
Having collected these measurements, the algorithm can be used to determine the extent of central sensitization and consequent therapeutic intervention.
Want know more about this research group and its studies? You can find it at paininmotion.be!
> From: Nijs et al., Acta Oncol 55 (2016) 659-663(Epub ahead of print). All rights reserved to Informa UK Ltd. Click here for the Pubmed summary.