Sensory function and pain in a population of patients treated for breast cancer

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Chronic pain is often reported after surgery for breast cancer. This study examined pain and sensory abnormalities in women following breast cancer surgery. Sensory tests were carried out on the operated and contra-lateral side in 55 women with chronic pain after breast cancer treatment and in a reference group of 27 pain-free women, who had also undergone treatment for breast cancer. Testing included a numeric rating score of spontaneous pain, detection and pain threshold to thermal and dynamic mechanical stimuli and temporal summation to repetitive pinprick stimulation. The neuropathic pain symptom inventory was applied for participants with chronic pain. The mean age was 58.6 years for the pain patients and 60.6 years for the pain-free patients. Thermal thresholds were significantly higher on the operated side than on the contra-lateral side in both groups and side difference in warmth detection threshold was significantly higher in the pain group than in the pain-free group (mean 3.8 degrees C vs. 1.1 degrees C, P=0.01). The frequency of cold allodynia was higher in participants with pain than in pain-free participants (15/53 vs. 1/25, P=0.01), and the frequency of temporal summation evoked by repetitive pinprick was higher in participants with pain than in pain-free participants (23/53 vs. 2/25, P=0.0009). The frequency of dynamic mechanical allodynia did not differ significantly between the two groups. These findings suggest that chronic pain after surgery for breast cancer is associated with sensory hyperexcitability and is a neuropathic pain condition.