Pilot Study to Evaluate the Effect of Aromatase Inhibitor Therapy on Pain Threshold in Breast Cancer Patients

Patients rated the intensity of each pressure sensation using a 0 to 100 numerical rating scale (0 = no pain, 100 = worst pain imaginable). Pain50 was defined as the amount of applied pressure in kilograms per square centimeter that evoked a pain intensity rating of 50 out of 100. Pain50 was assessed at baseline, 3 months, and 6 months. Change in Pain50 with estrogen depletion was determined.

To assess conditioned pain modulation, pressure equivalent to the patient's Pain50 was applied to the non-dominant thumbnail for 30 seconds (test stimulus), and the patient rated the intensity of the pressure on a 0-100 pain scale at 10 second intervals. Ten minutes later pressure (conditioning stimulus) was continuously applied to the dominant thumbnail for 60 seconds at the same Pain50 intensity. After 30 seconds, the test stimulus was again applied to the non-dominant thumbnail for 30 seconds and the patient rated the intensity every 10 seconds. Conditioned pain modulation magnitude was calculated as the difference (second minus first) in the mean of the 3 pain ratings to the test stimulus applied prior to and during the conditioning stimulus. Conditioned pain modulation was assessed at baseline, 3 months, and 6 months. Change over that time period was assessed. Higher conditioned pain modulation values indicate less efficient conditioned pain modulation.

Patients completed 4 measures at baseline, before aromatase inhibitor therapy initiation. (1) Depression: Center for Epidemiologic Studies-Depression, scores 0-60, higher scores reflect more depression. (2) Pain: 7 day Pain Diary, scores 0-10, higher scores reflect more pain. (3) Fatigue: Multidimensional Fatigue Inventory, scores 4-20, higher scores reflect more fatigue. (4) Sleep: Medical Outcomes Study-Sleep, scores 0-100, higher scores reflect worse sleep. Persistence with aromatase inhibitor therapy was assessed at the 6 month timepoint. Mean baseline values for each measure were calculated for the cohort that persisted with aromatase inhibitor therapy and the cohort that was non-persistent.

Estradiol is being assessed using an ultrasensitive gas chromatography tandem mass spectroscopy-based assay. The lower limit of detection of the assay is 0.625 pg/ml. For patients whose serum estradiol concentrations were below the lower limit of detection, the value of 0.625 pg/ml was used to calculate the mean estradiol concentration and standard deviation at both baseline and 3 months.