Association between salivary α-amylase activity and pain relief scale scores in cancer patients with bone metastases treated with radiotherapy.

Subjective assessment tools such as visual analog scales (VAS) or pain scores are commonly used to evaluate the intensity of chronic cancer-induced pain. However, their value is limited in some cases. We measured changes in VAS pain scores and salivary α-amylase (sAA) concentrations in cancer patients receiving radiotherapy for bone metastases to ascertain the correlation between these measures.We enrolled 30 patients with bone metastases attending a single institution from June 2010 to March 2011. All patients with cancer-induced bone pain received radiation therapy (RT) at the same dose (30 Gy) and fractionation (3 Gy/fraction, 5 days/week) for palliative pain relief. We assessed heart rate (HR), systolic and diastolic blood pressures (DBP/SBP) and VAS pain scores before (d0) and after five (d5) and ten fractions (d10) of irradiation. sAA and salivary cortisol (SC) concentrations were measured using a portable analyzer and automated chemiluminescence analyzer, respectively.Radiotherapy markedly decreased VAS scores from (82.93 ± 9.29) to (31.43 ± 16.73) mm (P < 0.001) and sAA concentrations from (109.40 ± 26.38) to (36.03 ± 19.40) U/ml (P <0.001). Moreover, there was a significant correlation between these two indices (P <0.01, r = 0.541). HR decreased by 6.5% after radiotherapy, but did not correlate with VAS scores (P >0.05). SC concentrations and BP did not change significantly during the study (P >0.05).The significant correlation between sAA concentrations and VAS pain scores identified in these preliminary results suggests that this biomarker may be a valuable, noninvasive and sensitive index for the objective assessment of pain intensity in patients with cancer-induced bone pain.