January 26, 2016 by Beth Gilbert, Clinical Pain Advisor
Calmare therapy (CT) may be an effective option for treating cancer-related neuropathic pain (CNP), according to a pilot study published in issue of theEuropean Journal of Oncology Nursing.1
Also known as scrambler therapy, the novel, noninvasive approach consists of applying surface electrodes around the surface of painful areas to ‘scramble’ afferent pain signals and replace them with synthetic ‘non-pain’ information.
The open-label study included 20 patients with the 3 most common causes of CNP: chemotherapy-induced peripheral neuropathy (CIPN; n=6), metastatic bone pain (n=7), and post-surgical neuropathic pain (n=7).
CT was applied for 40 minutes each day for 10 consecutive days; up to 2 days could be skipped at weekends. The primary endpoint was pain score, as evaluated on an 11-point numerical rating scale (NRS). Other measures included the Brief Pain Inventory (BPI) and opioid consumption.
Results at 1 month showed that CT yielded a 50% decrease in mean pain scores from baseline (3.7 vs 7.4, P < .001); 15 patients (75%) experienced a 30% or greater decrease in pain (30% – 50%, 45%; >50%, 30%). Pain relief was significant across pain subtypes, including CIPN (3.1 vs 6.1, P =.027), metastatic bone pain (3.1 vs 7.4, P = .018), and post-surgical neuropathic pain (5.2 vs 8.5, P = .028).
The approach was also associated with significant improvements in all 7 domains of the Brief Pain Inventory (BPI, P <.001 to P = .016)), and decreased use of opioid rescue therapy (P = .050). Half the patients treated expressed slight to moderate satisfaction with CT, while the other half remained neutral.
“The most important thing to note is that, without adding medications or increasing doses of existing prescriptions, this treatment provided patients with clinically significant relief, as 75% of patients experienced a 30% or greater improvement in pain,” Bob Twillman, PhD, executive director of the American Academy of Pain Management, told Clinical Pain Advisor.
Further Research Needed
The pilot study is primarily limited by its small sample size and open-label nature. Although larger studies can be conducted, the open-label aspect is not likely to be amenable to manipulation, Dr Twillman said.
“It would be really nice to have a double-blind, placebo-controlled, randomized clinical trial, but the nature of [CT] doesn’t really lend itself to even a single-blind trial. Thus, we will need to see a series of replications using a similar design. At some point, it might be possible to examine whether using Calmare therapy could enable patients to taper doses of opioids and other medications previously used to treat their pain,” Dr Twillman said.
According to study author Jee Youn Moon, MD, PhD, from the department of anesthesiology and pain medicine at Seoul National University Hospital College of Medicine in the Republic of Korea, other potential study limitations include barriers to CT access and placebo effect.
“Even though we included cancer patients who had life expectancy of greater than 3 months and tolerable health conditions, it might have been difficult for debilitated cancer patients to visit the outpatient department to obtain Calmare therapy for consecutive days, 2 weeks at a time,” Dr Moon pointed out.
“In addition, our study was not controlled for a possible placebo effect, although the pain reductionwas greater than that seen in previous placebo-controlled trials of cancer-related pain or chronic non-cancer pain,” he added.
Dr Moon also noted the need to investigate the effect of CT on specific symptoms, such as allodynia, hyperalgesia, tingling, and numbness. Studies are currently in development to evaluate the duration of CT efficacy in patients with various types of pain, and to determine its mechanism of action.
Multimodal Approach Remains Best
Similar devices, such as transcutaneous electrical nerve stimulation (TENS) units, have proven relatively ineffective in the treatment of pain conditions, Edward Michna, MD, anesthesiologist and director of pain clinical trials at Brigham and Women’s Hospital, and associate professor of anesthesia at Harvard Medical School in Boston Massachusetts, told Clinical Pain Advisor.
There is a possibility that Calmare therapy may decrease pain but not completely eliminate it. The best approach will continue to be a multimodal combination of medications, psychotherapy, and adjuvant therapies, Dr Michna added.
Although TENS was recently dropped from Medicare coverage, likely due to limited efficacy, this study suggests that there may be very good reasons to revisit that decision in certain circumstances, Dr Twillman pointed out.
“If this therapy is proven effective and covered by insurance companies, it could potentially revolutionize the treatment of cancer-related neuropathic pain. It could obviate the need to use opioids and other medications, with their potentially severe side effects, to treat this type of pain,” Dr Twillman concluded.
Lee SC, Park KS, Moon JY, et al. An exploratory study on the effectiveness of “Calmare therapy” in patients with cancer-related neuropathic pain: A pilot study. European Journal of Oncology Nursing. 2016;21:1-7. http://dx.doi.org/10.1016/j.ejon.2015.12.001.February 1, 2016