Thermal Testing in Bone Pain (TiBoP)

Bone is the third most common site of metastatic disease, after liver and lung, with ~75 per cent of these patients suffering from related pain. Cancer-induced bone pain (CIBP) remains one of the major clinical challenges in palliative care, with a number of possible reasons for this. Bone pain can have a significant impact on physical, psychological and social functioning (and so overall quality of life). The mechanisms of CIBP are complex and may have unique characteristics that are different from neuropathic and inflammatory pain - this has clear implications for managing CIBP effectively. Current gold standard treatment for CIBP is palliative radiotherapy (XRT). Radiotherapy is the current standard treatment for CIBP, although only 55% of patients will achieve adequate analgesia from palliative radiotherapy, and this can take up to 6 weeks to work. There has been considerable interest in how clinical signs and symptoms in pain translate into underlying mechanisms, and how this may be used to direct treatment more effectively. The clinical assessment of somatosensory processing used for neuropathic pain can be extensive, and burdensome for frail patients.

The investigators have developed a modified assessment for use in patients with cancer, that can be used in a hospital setting. The investigators clinical pilot work used detailed phenotyping of CIBP, to try and better understand underlying mechanisms and detect changes in somatosensory processing. The investigators found that changes in temperature sensitivity may predict pain relief from XRT. Following on from this the investigators propose to develop a simple bedside tool, suitable for use in the community, which will potentially identify patients most likely to benefit from radiotherapy.

Development of this tool requires adequate validation and evaluation so that it can be used as an aid to deciding which patients are more likely to benefit from radiotherapy. In those patients unlikely to benefit, early identification would allow use of other symptom control strategies in the community, minimising the burden of unnecessary hospital attendance, and avoiding the acute pain flare that can occur with XRT.

The investigators hypothesis is that alterations in thermal sensitivity will reflect important changes in underlying pain neurobiology that will make that patient more, or less, likely to get effective analgesia from XRT. Assessment of CIBP There have been recommendations suggested for the use of pain measurement tools and methods in clinical practice to try and include the wider aspects of the pain experience (www.immpact.org). In patients with cancer, it is important to minimise any burden from assessment. We have therefore use a very a simple approach to try and capture the important elements of CIBP and its impact. This consists of a number of validated self report questionnaires (see below), plus a measurement of skin sensitivity to warm and cool (40°C, 25°C), as identified from our previous work as potential predictors of treatment response to XRT.

Self report measures include: the Brief Pain Inventory (BPI); The Short-Form McGill Pain Questionnaire (SF-MPQ-2); the Hospital Anxiety \& Depression Scale (HADS); the Distress Thermometer; the EORTC health-related quality of life questionnaire for bone metastases.

Patients with CIBP will be assessed prior to XRT, then at 2, 6 and 12 weeks after XRT.