Robb, K.A., Bennett, M.I., Johnson, M.I., Simpson, K.J., & Oxberry, S.G. (2008). Transcutaneous electric nerve stimulation (TENS) for cancer pain in adults. Cochrane Database of Systematic Reviews, 3, CD006276.

To determine the effectiveness of transcutaneous electric nerve stimulation (TENS) in management of cancer-related pain and to provide guidance for optimal parameters of TENS for pain relief

Databases searched were The Cochrane Library, MEDLINE, Embase, CINAHL, AMED, PEDro, and PsycINFO. Hand-searching of reference lists of articles retrieved was also done.

MeSH terms were Neoplasms [*complications]; Pain [etiology;*therapy] Randomized controlled trials as Topic; Transcutaneous Electric Nerve Stimulation (TENS) [*methods] Adults; Humans. An extensive listing of search strategies and terms for each database used are provided.

Studies were included in the review if they

• Were a randomized controlled trial (RCT) where the control group was either receiving no treatment or no active stimulation/placebo
• Evaluated TENS administered with a standard device that delivered mono or biphasic electrical currents
• Reported on TENS delivery that provided a strong but comfortable sensation in either the area where pain was present or over nerve bundles proximal to the site of pain
• Reported on adult patients with cancer-related pain
• Reported pain outcomes.

Studies were excluded if they

• Compared TENS with active treatment
• Used percutaneous electrical stimulation
• Evaluated TENS delivered at a reported intensity that was mild or barely perceptible.

The search identified 36 studies from 1975 to 2008, and reference lists identified an additional 7 studies. Only two studies met all inclusion criteria. Study quality was assessed using the Oxford Quality Scale (Jadad scale).

• The final sample of two studies included in the review encompassed a total of 54 patients: 41 entered in one study and 13 in the other.
• All patients were 18 years of age or older and had experienced persistent cancer-related pain for three months or longer.
• One study was done in patients receiving palliative care at the end of life.

The majority of studies initially retrieved from the search were eliminated due to design that was either not an RCT or where clinical results were not reported. No meta-analysis could be done due to the small sample size with final studies included. In one study, TENS was compared to sham TENS in women. The only outcome measure with significant differences between groups was one dimension of a patient satisfaction questionnaire. In the other study, there were no significant differences between groups.

No conclusions regarding the effectiveness of TENS could be made due to the lack of studies that met criteria.

This review was limited by the inclusion criteria that TENS had to be compared to no treatment. The ethics of having such a control or placebo group in patients with chronic pain and in end-of-life care is questionable, and the inability to find enough studies that met this strict criteria is not surprising. Results were inconclusive due to lack of suitable RCTs.

There is little data to demonstrate effectiveness of TENS for cancer-related pain. In patients with chronic pain, the insistence upon a placebo control group in an RCT is not reasonable and appropriate, and such limitations will not serve to advance knowledge in this area. Additional research with adequate sample sizes is needed in this area.