Transcutaneous Electric Nerve Stimulation (TENS) for cancer pain in adults
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To establish the effectiveness of TENS in the management of cancer‐related pain in adults.
Background
The World Health Organisation has estimated that four million people in the world suffer from cancer pain. There are many reasons why a patient with cancer may experience pain and these include pain associated with the disease, pain associated with the cancer treatments and any associated co‐morbid conditions. The mainstay of cancer pain management has predominantly used the biomedical approach including drug therapy, medical or surgical treatments (Turk 1998). However, It is clear that cancer‐related pain is complex and multidimensional and there is a definite need for a multi‐disciplinary team approach, utilising non‐pharmacological and innovative approaches. Physical treatments such as electrical stimulation may have a role for a significant number of patients (Simpson 2000).
Transcutaneous electrical nerve stimulation (TENS) is a non‐invasive therapeutic intervention which has been widely used for many years to manage a range of acute and chronic pain problems (Johnson 2002; Walsh 1997). TENS is used in a variety of clinical settings and has gained popularity with both patients and healthcare professionals of different disciplines. TENS devices have many advantages in that they are portable, easy to use, have relatively few side‐effects or contra‐indications and allow the user autonomy over their pain control.
There are several types of TENS application which are used in clinical practice but the two most common are 1) high frequency, low intensity (conventional) TENS and 2) low frequency, high intensity (acupuncture‐like) TENS. More recent developments of TENS have evolved with the aim of improving the efficacy of TENS and these include 'burst' and 'modulated' modes of stimulation. The clinical use of conventional TENS is underpinned by the gate control theory of pain (Melzack 1965) which suggests that there is a 'gating' mechanism in the dorsal horn of the spinal cord which can control nociceptive signals and ultimately influence the pain experience. In summary, the stimulation of large diameter (A‐beta) afferent fibres is thought to 'close the gate' and reduce the perception of pain. Acupuncture‐like TENS mainly stimulates A‐delta and C fibres and is therefore thought to achieve pain control mostly through the descending pain suppression system. In essence, acupuncture‐like TENS is thought to help to close the gateway of pain transmission and hence result in a reduction in pain.
There are currently five Cochrane Systematic Reviews addressing the use of TENS for non‐cancer pain (Carroll 2001; Khadilkar 2005; Osiri 2000; Proctor 2005) as well as excellent review articles (Bjordal 2003; Johnson 2001; Reeve 1996). There is some controversy over the use of TENS in chronic pain, with most review papers citing the need for further research using large multi‐centre RCTs. The single available review in cancer pain addresses non‐drug approaches for symptoms related to cancer and includes the evidence on TENS for pain management (Pan 2000). Although experts in the field suggest that TENS has an important role in the management of cancer‐related pain (Filshie 2000) it is clear that there is currently no guidance for clinicians on the use of TENS for oncology and palliative care patients. The clinical benefit of TENS for cancer patients with pain remains controversial. A Cochrane review of TENS in acute pain is currently being undertaken (Walsh 2006).
The aim of this Cochrane review is to determine the effectiveness of TENS in the management of cancer‐related pain and to provide guidance for healthcare professionals and patients on the optimal parameters of TENS for best pain relief.
Objectives
To establish the effectiveness of TENS in the management of cancer‐related pain in adults.
Methods
Criteria for considering studies for this review
Types of studies
All randomised controlled trials (RCTs) (crossover and parallel design) investigating the use of TENS for the management of cancer‐related pain in adults where the control (placebo) group is clearly defined and is either:
1) no active stimulation or,
2) no treatment.
No trials only comparing TENS with active treatment will be included.
Types of participants
Participants will be 18 years of age or older. They will have experienced cancer‐related pain unspecified or persistent cancer treatment related pain, or both, for greater than or equal to three months after any anti‐cancer treatment has concluded. Pain will be classified based on commonly used verbal rating scales or pain interference scales. All levels of pain at baseline will be included in our primary analysis. We intend to review pain described as moderate or above at baseline as part of our subgroup analysis, assuming data allows this.
Types of interventions
Only studies that evaluate transcutaneous not percutaneous electrical stimulation for the management of cancer pain will be included. A "standard TENS device" delivers monophasic or biphasic pulsed electrical currents in the mA range.
We consider Conventional TENS as administered using any TENS device which delivers a "strong but comfortable" electrical sensation either
i) in an area of pain which is sensate, or
ii) over nerve bundles proximal to the site of pain.
Any parameters of treatment which result in this will be considered, as will any duration and frequency of treatment. TENS is typically delivered using at least two surface electrodes; however, studies involving single electrical probes (i.e. TENS pens) will also be included. This may also involve the placement of electrodes over an area of pain that co‐incidentally includes acupuncture points. Our definition of appropriate TENS delivery also includes use of Neuromuscular Electrical Stimulation devices (NMES) and Interferential current devices. Given the above physiological criteria, TENS delivered at intensities reported to be "barely perceptible" or "mild" will be excluded.
Types of outcome measures
The primary outcome measure is patient reported pain using validated scales (e.g. visual analogue scales, numerical rating scales).
Secondary outcome measures can include any of the following:
-
patient satisfaction,
-
function,
-
range of movement,
-
quality of life,
-
mood,
-
pain coping,
-
sleep,
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analgesic consumption,
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hospital attendance and other healthcare interventions e.g. physiotherapy visits, hospice admissions,
-
adverse events ‐ major and minor.
Ideally outcome measures should be taken before, during and after stimulation. However, we will not exclude those trials where this is not done. We intend to perform subgroup analyses on outcomes of greater than or equal to 30% reduction in pain from baseline should data allow this.
Search methods for identification of studies
The Cochrane Library, MEDLINE, EMBASE, CINAHL, PsychINFO, AMED and PEDRO physiotherapy databases are to be searched. Detailed search strategies will be developed for each database searched, based on the strategy for MEDLINE but revised appropriately for each database. Various foreign language databases will also be searched with the terms outlined below. Reference lists of eligible trials will also be reviewed to identify further studies. Relevant randomised controlled trials will be identified using the following search strategy combined with the Cochrane Sensitive Search Strategy for RCTs {as published in Appendix 5b in the Cochrane Reviewers' Handbook for systematic reviews (Alderson 2004)}:
MEDLINE search (1950 to present) ‐ via Dialog Datastar:
1. TRANSCUTANEOUS ADJ ELECTRIC ADJ NERVE ADJ STIMULATION
2. TRANSCUTANEOUS‐ELECTRIC‐NERVE‐STIMULATION.DE.
3. TNS
4. PERCUTANEOUS ADJ ELECTRIC ADJ NERVE ADJ STIMULATION
5. ELECTRIC ADJ STIMULATION ADJ THERAPY
6. ELECTRIC‐STIMULATION‐THERAPY.DE.
7. ELECTRIC ADJ STIMULATION
8. ELECTROSTIMULATION
9. ELECTROANALGESI$
10. ELECTROTHERA$
11. ELECTROMAGNETI$
12. INTERFERENTIAL
13. REBOX
14. CODETRON
15. LIKON
16. 1 OR 2 OR 3 OR 4 OR 5 OR 6 OR 7 OR 8 OR 9 OR 10 OR 11 OR 12 OR 13 OR 14 OR 15
17. CANCER$
18. NEOPLASMS#.W..DE.
19. TUMOUR$
20. TUMOR$
21. ONCOLO$
22. CARCINOMA$
23. MALIGNAN$
24. 17 OR 18 OR 19 OR 20 OR 21 OR 22 OR 23
25. PAIN$
26. PAIN#.W..DE.
27. PAIN ADJ MEASUREMENT
28. PAIN‐MEASUREMENT.DE.
29. PAIN ADJ SCALE
30. 25 OR 26 OR 27 OR 28 OR 29
31. 16 AND 24 AND 30
Data collection and analysis
Study selection
Two review authors (SO, MB) will independently select the trials to be considered in the review following the literature searches as outlined above. We do not anticipate large numbers of trials and we will therefore not rely on abstracts alone to identify relevant articles based on our inclusion criteria. Disagreement about inclusion or exclusion of individual studies will be resolved by discussion between the review authors in the first instance. If this remains unresolved a third member of the review team will make the final decision (MJ).
Data extraction
For each included trial we will complete a data extraction sheet standardised for this review. Information to collect will include authors, participants, trial design, characteristics of interventions (TENS settings, application, treatment schedule, concurrent interventions), adverse effects and baseline and end of study outcomes. We anticipate that two pairs of review authors (MB, KS, MJ, HR) will complete data extraction. Differences between review authors will be resolved by referring back to the original article and establishing consensus. Additional information will be sought from authors of relevant trials if data is incomplete.
Analysis
The quality of the studies will be assessed independently by two review authors (MB, KS) using the validated five‐point Oxford Quality Scale (Jadad 1996). An overall score for each article is reached using this scale which considers the method of randomisation, blinding and the description of withdrawals or drop‐outs. Differences in scoring will be resolved by consensus.
Treatment effect measures
Data from the outcomes from each trial will be pooled where appropriate to arrive at an overall estimate of the effectiveness of TENS. Intention‐to‐treat data from the individual trials will be used when possible. Mean scores and standard deviations will be estimated if outcomes are reported in graphical form only. All data from individual trials will be entered in the RevMan 4.2 software programme. For continuous data, results will be presented as weighted mean differences (WMD). However, as we anticipate that many different pain scales may be used for the same outcome we will need to present this data using standardised mean differences (SMD). For dichotomous data, relative risk (RR) will be used.
Investigation of heterogeneity
Heterogeneity will be assessed using the Chi square test with further assessment (I2 test) as appropriate. Fixed Effect models will be used unless heterogeneity is significant, in which case Random Effects models will be used. Publication bias is unlikely to be assessed given such a small number of potential studies.
Subgroup and sensitivity analyses
Subgroup and sensitivity analyses will be attempted to determine the effects of the method of TENS application, methodological quality, patient characteristics and treatment duration on outcomes. We intend to perform sensitivity analysis removing trials that compare TENS to no treatment. Where the data allows, we also intend to perform subgroup analyses on outcomes of greater than or equal to 30% reduction in pain from baseline and on participants with pain scores of moderate or above at baseline.
