Background: Certain types of cancer pain have remained hard to control even by highly skilled pain experts. Uncontrolled cancer pain can have severe effects on quality of life, physical functioning, and leads to psychological distress. From this perspective, nonpharmacologic modalities of treatment are important. Neuromodulatory techniques, such as transcutaneous electrical nerve stimulation and scrambler therapy (ST), have gained popularity in recent times. ST is a relatively new therapy that has been used for the management of cancer pain resistant to pharmacologic management. Several studies have shown that ST is an effective therapy for this type of pain.
Objectives: The aim of this study was to detect possible gaps in the literature regarding the efficacy of ST for cancer pain and formulate recommendations for research through a systematic review of the literature.
Study design: A systematic review of the literature was performed following the recommendations of the PRISMA Statement.
Methods: PubMed and EMBASE were searched for studies that met the inclusion criteria using a predetermined search strategy. Reference list of retrieved studies and Google Scholar were used to verify that no relevant studies had been omitted. Data were extracted from the studies with a data extraction sheet. A qualitative analyses of the extracted data was undertaken.
Results: Twenty-seven studies were retrieved. Ten were articles that were categorized as literature reviews, including 7 general literature reviews not following a specific review methodology, 1 editorial, and 2 systematic reviews. Seventeen were original studies, including 2 single-arm trials, 1 randomized controlled trial, 4 pilot trials, 4 case reports, 2 retrospective studies, and 4 prospective studies. By and large, the available literature supports the use of ST as an effective therapy for the management of refractory cancer pain. However, the level of evidence for its application to cancer pain is not particularly strong, and improvement in pain with ST may even be owing to a placebo effect.
Limitations: This study was not a meta-review. Because of the limited number of clinical trials on ST in cancer pain, such a meta-review could not meaningfully be performed.
Conclusions: Methodologically sound, large randomized control trials are needed in this area. However at this stage, ST may be considered a good option for cancer patients suffering from pain that does not respond to pharmacologic treatment.
Key words: Scrambler therapy, cancer, cancer pain, neuropathic pain, Calmare therapy, evidence, noninvasive pain treatment, chronic pain.