Bennett, M.I., Johnson, M.I., Brown, S.R., Radford, H., Brown, J.M., & Searle, R.D. (2010). Feasibility study of transcutaneous electrical nerve stimulation (TENS) for cancer bone pain. Journal of Pain, 11, 351–359.

To determine the feasibility of conducting a larger phase III trial to investigate the effectiveness of TENS for control of cancer-related bone pain

Patients were randomized to receive either active TENS at the first application and placebo TENS at the second application, or vice versa. Researchers responsible for outcome assessments were blinded to patient group. Placebo TENS was delivered using devices that were identical in appearance but delivered no current output. Patients were informed that sometimes they would feel a tingling sensation and sometimes they might not feel this. Patients were instructed not to tell the research observer any sensations they were feeling. Pain intensity measures were obtained at baseline, then repeated after 30 and 60 minutes of TENS application. Patients returned for the second TENS application two to seven days later and experienced an identical procedure. TENS application was given using a single channel device, and placement was based on recommendations for conventional TENS of the International Association for the Study of Pain. Pain was assessed at rest and on a patient-specified movement. Patients continued their current pain medication regimen.

• The study reported on a sample of 24 randomized patients, with 19 analyzed.
• Mean patient age was 72 years, with a range of 40–91 years. 
• The sample was 75% male (18) and 25% female (6). 
• The majority of patients had prostate cancer. Additional types included breast, lung, thyroid, and renal.
• All patients had radiologic evidence of bone metastases, pain rated as at least 3 on a 10-point rating scale, and an expected survival of longer than four weeks.
• Most (87%) were being treated with strong opioids, including morphine, fentanyl, or oxycodone, 79% had previous radiotherapy, and 33% had received biophosphonates.
• The most common sites of painful bone metastases were pelvis, lumbosacral spine, and lower limbs.
• The majority of patients had an Eastern Cooperative Oncology Group performance status of 1 or 2.
• Patients were on stable pain medication regimens.

• Multisite
• Outpatient setting in the United Kingdom

A randomized, controlled, double-blind, crossover design was used.

• Numerical pain rating scale (1–10)
• Verbal rating scale (four categories from no pain to severe pain)
• Short Form McGill Pain Questionnaire (SF-MPQ)
• Patient satisfaction questionnaire designed by authors regarding benefit, ease of use, and impact on pain or rest

The mean pain change in pain intensity score for active TENS was –0.84 compared with placebo TENS of –2.16. The mean change with movement was –2.32 for active TENS compared with placebo change of –2.0. at one hour. The mean pain relief on movement was higher with active TENS. The difference in proportion of patients who reported good or very good pain relief on movement with active TENS by verbal ratings was 36.8% (95% CI 7.5–66.2%). There were no clear patient preferences between active and placebo TENS. Three patients experienced adverse events, increased pain with TENS application, that were deemed likely to be or definitely related to TENS use.

TENS has the potential to provide improved pain relief on movement in patients with bone pain.

The study had a small sample, with less than 30 patients.

The purpose of this study was to determine feasibility and use findings to plan for a phase III study, rather than to determine intervention effect. Findings suggest that TENS may be more effective in pain relief on movement than for pain relief at rest for bone pain. Findings also showed an effect on the measure of pain relief, but not on the measure of pain intensity. This suggests that pain relief measurement may be more useful in clinical trials than just measurement of pain severity at given points in time.