Spinal cord stimulation for cancer-related pain in adults

Cancer-related pain places a heavy burden on public health with related high expenditure. Severe pain is associated with a decreased quality of life in patients with cancer. A significant proportion of patients with cancer-related pain are under-treated.There is a need for more effective control of cancer-related pain. Spinal cord stimulation (SCS) may have a role in pain management. The effectiveness and safety of SCS for patients with cancer-related pain is currently unknown.

This systematic review evaluated the effectiveness of SCS for cancer-related pain compared with standard care using conventional analgesic medication. We also appraised risk and potential adverse events associated with the use of SCS.

We searched the following bibliographic databases in order to identify relevant studies: the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Libary (from inception to 2012, Issue 6); MEDLINE; EMBASE; and CBM (Chinese Biomedical Database) (from inception to July, 2012). We also handsearched relevant journals.

We planned to include randomised controlled trials (RCTs) that directly compared SCS with other interventions with regards to the effectiveness of pain management. We also planned to include cross-over trials that compared SCS with another treatment. We planned to identify non-randomised controlled trials but these would only be included if no RCTs could be found.

The initial search strategy yielded 430 articles. By scrutinising titles and abstracts, we found 412 articles irrelevant to the analytical purpose of this systematic review due to different scopes of diseases or different methods of intervention (intrathecal infusion system; oral medication) or aims other than pain control (spinal cord function monitoring, bladder function restoration or amelioration of organ metabolism). The remaining 18 trials were reviewed as full manuscripts. No RCTs were identified. Fourteen sporadic case reports and review articles were excluded and four before-and-after case series studies (92 participants) were included. Two review authors independently selected the studies to be included in the review according to the pre-specified eligibility criteria. A checklist for methodological quality of non-randomised controlled trials was used (STROBE checklist) and all review authors discussed and agreed on the inclusion of trials and the results of the quality assessment.

Four before-and-after case series studies (a total of 92 participants) met our criteria for inclusion. All included trials adopted a visual analogue scale (VAS) to evaluate pain relief. Heterogeneity existed in terms of baseline characteristics, electrode and stimulator parameters, level of implantation and route of implantation; data reporting was different among all trials. In two trials, pain relief was achieved in 76% (48/63) of patients at the end of the follow-up period. In the third trial, pre-procedure VAS was 6 to 9 (mean 7.43 ); the one-month post-implant VAS was 2 to 4 (mean 3.07); the 12-month post-implant VAS was 1 to 3 (mean 2.67). In the fourth trial, the pre-procedure VAS was 6 to 9 (mean 7.07); 1 to 4 (mean 2.67) at one-month; 1 to 4 (mean 1.87) at 12 months. Analgesic use was largely reduced. The main adverse events were infection of sites of implantation, cerebrospinal fluid (CSF) leakage, pain at the sites of electrodes, dislodgement of the electrodes and system failure, however, the incidence in patients with cancer could not be calculated. Since all trials were non-randomised controlled trials, they carried risk of all types of bias.

Current evidence is insufficient to establish the role of SCS in treating refractory cancer-related pain. Future randomised studies should focus on the implantation of SCS in patients with cancer-related pain.