Bennett 2010.

Methods	Randomised, placebo‐controlled crossover feasibility study Randomised to active then placebo TENS or placebo then active TENS Sample size: 24 patients randomised, 19 received both applications, 10 in active then placebo arm, 9 placebo then active arm Active or placebo TENS applied to site of bone pain by a medical researcher for continuous 60 minute period After 2 to 7 days placebo or active then applied for 60 minutes Outcome measures recorded at baseline, after 30 minutes and sixty minutes by the patient and research nurse observer both of whom were blinded, telephone follow up after 48 hours. Patient satisfaction and preference questionnaires on completion of study. SF‐MPQ completed before and after active/placebo TENS application
Participants	Patients with cancer referred to specialist palliative care services in 2 UK cities Inclusion criteria: over 18 years of age, diagnosis of any cancer with bone metastases, radiological evidence of bone metastases, estimated survival of more than 4 weeks, pain intensity of at least 3 out of 10 on NRS at rest and /or movement Exclusion criteria: unable to complete patient related information on entry, no ongoing cancer and TENS contraindicated as per UK Chartered Society of Physiotherapists Guidance for the Clinical Use of Electrophysical Agents, significant change (increase or decrease in opioid dose of 30% or more or addition or removal of co analgesic) to analgesic medication within 48hours of baseline Mean age (years) 72 (median 74 range: 40‐9) Male: 18, female: 6 Primary cancer: prostate (n = 12), breast (n = 5), lung (n = 3), thyroid (n = 1), renal (n = 1). other (n = 1) ECOG performance: 1 (n = 3), 2 (n = 11), 3 (n = 9), 4 (n = 1) Previous and current treatment: radiotherapy (n = 19), bisphosphonates (n = 8), strong opioids (n = 21), paracetamol (n = 15) NSAID (n = 7) strong opioid and paracetamol or NSAID (n = 16) Median 193 days between radiotherapy and randomisation Dropouts: After 1st treatment (n = 5) withdrawal due to deteriorating performance status unrelated to TENS (n = 3), withdrawal due to pain during TENS (n = 2), pain during active TENS (n = 1), pain during placebo (n = 1)
Interventions	Single channel TENS device and 2 self adhering hypoallergenic gel pads approximately 5 x 5 cm in size placed between 5 and 10 cm apart over area of pain on an area of skin in good condition without signs of altered sensation Parameters: continuous pulse pattern, pulse width: 200 microseconds, pulse frequency 80Hz, intensity increased until TENS sensation strong but comfortable Duration; 2 x 60 min, once placebo, once active, 2‐7 days between treatments
Outcomes	NRS pain relief and pain intensity, VRS pain relief and pain intensity at baseline 30 minutes and 60 minutes, SF‐MPQ before and after application, after second application: patient satisfaction questionnaire (TENS beneficial, TENS easy to use, most impact at rest or on movement), which application provided most benefit, which outcome scale best represented experience of pain intensity and relief
Notes	Quality: 4
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "patients were randomized via the Clinical Trials Research Unit (University of Leeds) central randomization system, using stratified permuted block randomization"
Allocation concealment (selection bias)	Low risk	Comment: A "central randomization system" was used.
Blinding (performance bias and detection bias) All outcomes	High risk	Quote: 'After both TENS applications had been completed, 11 out of 19 patients thought that placebo TENS was used in the study and of these 11 patients, 10 correctly identified the placebo. Blinding was judged by the research nurse observer to have been successfully concealed to them in 15 of 19 patients (i.e. the patient did not reveal the sensation that they were experiencing)." "The medical researcher applying the TENS device was not blind to the intervention but did not take part in patient assessments."
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "After both TENS applications had been completed, 11 out of 19 patients thought that placebo TENS was used in the study and of these 11 patients, 10 correctly identified the placebo. Blinding was judged by the research nurse observer to have been successfully concealed to them in 15 of 19 patients (i.e. the patient did not reveal the sensation that they were experiencing)."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "The medical researcher applying the TENS device was not blind to the intervention but did not take part in patient assessments." "Blinding was judged by the research nurse observer to have been successfully concealed to them in 15 of 19 patients (i.e. the patient did not reveal the sensation that they were experiencing)." Comment: the research nurse observer was the assessor and may have been unblinded in some participants
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Five patients withdrew from the study after first treatment. Three were withdrawn by their clinician due to deteriorating performance status (deemed unrelated to the TENS application) and 2 patients withdrew because of increased pain during TENS application: 1 following active TENS and 1 following placebo TENS." Comment: all those who did complete were excluded from primary analysis. The missing outcome data are balanced in numbers between intervention groups with similar reasons for missing data across groups
Selective reporting (reporting bias)	Low risk	Comment: although the protocol was not available, the study reports on all pre‐specified and relevant outcomes