BACKGROUNDSubjective 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.

METHODSWe 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.

RESULTSRadiotherapy 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).

CONCLUSIONSThe 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.