Transperineal prostate biopsy is a safe and effective method of diagnosing prostate cancer. When performed under local anaesthesia in an outpatient setting, it can cause significant pain, particularly during the periprostatic nerve block - the injection of local anaesthetic around the prostate. Better pain management during this procedure may improve patient comfort and encourage wider use of the transperineal approach.

Transcutaneous electrical nerve stimulation (TENS) is a non-invasive, low-cost method of pain relief that works by delivering mild electrical impulses through the skin. A preceding pilot study at our centre (n=84) found that TENS used alongside local anaesthesia was associated with significantly lower pain scores during periprostatic nerve block and biopsy sampling, with no device-related complications.

This study aims to confirm these findings in a larger, formally powered, triple-blind, randomized controlled trial. Participants will be randomly assigned to receive either active TENS or sham TENS (electrodes applied but no electrical current delivered) in addition to standard local anaesthesia. Neither the participant, the operating urologist, nor the nurse recording pain scores will know which group the participant is in.

Pain intensity will be assessed at four stages of the procedure using a 0-10 numeric rating scale. Participants will be followed up at 30 days after the biopsy.

This is a single-centre, prospective, randomized, triple-blind, sham-controlled, two-parallel-group superiority trial. The study builds on a preceding pilot study (TENS 1, n=84) which demonstrated large effect sizes for TENS-associated pain reduction during transperineal prostate biopsy under local anaesthesia.

Triple-blinding is achieved through a three-component procedure: amplitude titration is completed before the operating urologist enters the procedure room; a physical opaque screen is placed between the TENS device and the operative field; and participants are instructed not to verbalise device-related sensations during the procedure.

The primary outcome is NRS pain score during periprostatic nerve block, assessed within 30 seconds of completion of bilateral periprostatic infiltration by an independent outcome assessor blinded to allocation.

Exploratory outcomes include preoperative pain catastrophizing, preoperative anxiety (STAI-S), and the effect of prior biopsy experience on procedural pain.

Inclusion Criteria:

• Male patients aged 40 years or older
• Indication for prostate biopsy: elevated serum PSA (as per institutional protocol and EAU guidelines) or abnormal digital rectal examination (DRE)
• Suspicious lesion on multiparametric MRI classified as PI-RADS score 3 or higher (version 2.1)
• Scheduled for transperineal MRI-ultrasound fusion-guided prostate biopsy under local anaesthesia
• Ability to provide written informed consent

Exclusion Criteria:

• Prior treatment for prostate cancer (surgical, radiotherapy, hormonal or focal therapy)
• Contraindications to TENS: cutaneous damage or dermatologic conditions at electrode application sites; cardiac pacemaker or implantable cardioverter-defibrillator (ICD); uncontrolled cardiac arrhythmia or congestive heart failure; history of epilepsy or seizure disorder; metallic implants near the stimulation site; malignancy at or near the stimulation site
• Contraindications to transperineal biopsy: active urinary tract infection; bleeding disorder or ongoing anticoagulation not amendable to bridging; anatomical abnormalities preventing safe prostatic access
• Known allergy or intolerance to local anaesthetic agents or biopsy-related materials
• Severe comorbidities or unstable medical condition compromising procedural safety
• Inability to complete questionnaires
• Participation in another interventional clinical trial within 30 days prior to enrolment

De-identified individual participant data underlying the results reported in the primary publication will be made publicly available at the Open Science Framework (OSF) at the time of publication.

Beginning at time of publication, no end date.

Publicly available without restriction via Open Science Framework (OSF).

Triple-blind design. Participant blinding: identical electrode placement; device produces no sound and display is not visible. Care Provider (operating urologist) blinding: amplitude titration completed before operator enters room; opaque physical screen between device and operative field throughout procedure. Outcomes Assessor (Nurse B) blinding: independent nurse with no access to randomization list records all NRS scores. Investigator blinding: statistician receives data coded A/B until analysis lock. Only Nurse A (device operator) knows allocation.