Cancer-related pain, which always manifests as severe and intractable pain, is the most disruptive cancer-related event to the cancer patient’s quality of life [
1,
2]. The overall prevalence of pain in patients with cancer had been reported as > 50% [
2]. In a 2014 systematic review of 19 studies, the pooled prevalence of breakthrough cancer-related pain was 59.2%, which ranged from 39.9% in outpatient clinics to 80.5% in hospices [
3]. A Cochrane systematic review published in 2015 reported that 40% of patients with early or intermediate stage cancer and 90% with advanced cancer suffer from moderate or severe pain [
4]. Although the World Health Organization (WHO) has given more attention to control cancer pain for several decades, under-treatment of cancer pain has been widely documented [
5]. To date, opiate drugs remain the gold standard for treating moderate to severe pain or breakthrough pain resulting from cancer and are recommended strongly for treating cancer pain [
6]. Nevertheless, long-term use of opioid drugs extensively inhibits the immune system [
7] by leading to T lymphocyte apoptosis [
8], inhibiting activation of T lymphocyte proliferation and secretion of IL-2 [
9,
10]. Opioid-induced immunosuppression has become the most significant drug-induced medical problem or side effect of opiate drug administration [
11]. In addition, chronic pain (including cancer pain) also has an inhibitory effect on the immune system [
12]. At present, an overwhelming majority of cancer patients are simultaneously bothered by both cancer-related pain and opioid-induced immunosuppression.
Acupuncture has been accepted worldwide given its effectiveness in treating various pains. A systematic review published recently demonstrated that acupuncture is effective in relieving cancer-related pain, particularly malignancy-related and surgery-induced pain [
13]. Acupuncture plus drug therapy is more effective than conventional drug therapy alone for cancer-related pain [
14]. Transcutaneous electrical nerve stimulation (TENS) has been widely used in acute or chronic pain, is effective in 67% of different types of pain [
15], and may be a novel treatment for cancer bone pain [
16]. However, the analgesic effects of TENS for chronic pain or cancer pain are obscure due to a lack of suitable randomized controlled trials (RCTs) [
17,
18]. Transcutaneous electrical acupoint stimulation (TEAS), also called acupuncture-like TENS or acupuncture-type TENS, is a novel therapy combined acupoint stimulation and TENS technique. TEAS has become more popular than acupuncture worldwide given its non-invasive feature. Moreover, it has been reported that the analgesic effect of TEAS was similar to acupuncture on postoperative surgical pain relief in gynecologic oncology patients [
19]. Previous clinical studies also demonstrated a positive effect of TEAS analgesia in patients with labor pain and postoperative pain [
20‐
23]. However, there is no direct evidence on the effect of TEAS on cancer-related pain. Moreover, acupuncture and TEAS has immunomodulatory effects [
24,
25], but whether TEAS combined with opioid drugs will helpful to improve immune function and reduce other opioid-related side effects remains unclear. Rigorously designed and large multicenter RCTs are required to assess the value and potential advantage of TEAS in the management of cancer-related pain.