Acupuncture for clinical improvement of endometriosis‑related pain: a systematic review and meta‑analysis

Endometriosis is a chronic gynecologic condition characterized by the presence of endometrial tissue outside the uterine cavity, affecting between 10-15% of women of reproductive age. This condition causes chronic inflammation, severe pelvic pain, and can lead to infertility, significantly impacting patients' quality of life. Conventional treatments include analgesics, anti-inflammatories, hormonal therapy, and surgery, but they often have limited efficacy and considerable side effects, with discontinuation rates of 25-50% due to adverse reactions such as bleeding, weight gain, and depression.

This study represents a comprehensive meta-analysis that evaluated 14 randomized clinical trials involving 793 patients to determine the efficacy of acupuncture in treating endometriosis-related pain. The researchers conducted a systematic search across eight international databases, including PubMed, EMBASE, and Cochrane, identifying studies that used acupuncture exclusively as an intervention, distinguishing it from previous reviews that included combination therapies.

The methodology included different acupuncture modalities: traditional body acupuncture, electroacupuncture, auricular therapy, warm needling, and fire needling. The most frequently used points were Zhongji (CV-3), Guanyuan (CV-4), and Qihai (CV-6) of the Ren meridian, and Sanyinjiao (SP-6) of the Spleen meridian. These points were selected for their anatomic location in the lower abdomen and their traditional therapeutic function in treating reproductive disorders and pain relief.

The results demonstrated significant efficacy of acupuncture across multiple outcomes. The primary analysis showed a substantial reduction in pain intensity (SMD = -1.10, 95% CI: -1.45 to -0.75, p<0.001), indicating a clinically relevant effect on pain control. The clinical response rate was higher in the acupuncture group (RR = 1.25, 95% CI: 1.09-1.44, p=0.02), suggesting that more patients experienced clinically meaningful improvement. Additionally, a reduction was observed in serum CA-125 levels, an inflammatory marker associated with endometriosis (SMD = -0.62, 95% CI: -1.15 to -0.08, p=0.024).

Subgroup analyses revealed important differences among acupuncture modalities. Auricular therapy demonstrated the best results for pain reduction, followed by body acupuncture and electroacupuncture. For clinical response rate, auricular therapy and warm needling showed superiority, while electroacupuncture and fire needling did not show statistically significant differences compared to controls. These findings suggest that different techniques may have variable efficacy, guiding the selection of the most appropriate modality for each patient.

Proposed mechanisms for the effects of acupuncture include modulation of prostaglandins, β-endorphins, dynorphins, and substance P, all involved in pain perception and transmission. Acupuncture has also been shown to regulate endocrine function through modulation of estrogen receptors, influence the immune response by reducing inflammatory cytokines, and improve local blood circulation. Animal model studies have confirmed these mechanisms, showing normalization of electrolytes and reduction of inflammatory markers after acupuncture treatment.

The clinical implications are substantial, offering robust evidence for the use of acupuncture as an effective and safe treatment for endometriosis-related pain. Acupuncture presents significant advantages as an alternative or adjunct to conventional treatments, especially considering its favorable safety profile and absence of significant side effects. The results suggest that acupuncture may be considered first-line treatment for patients who do not tolerate or do not respond adequately to pharmacologic therapy.

Despite the promising results, the study has important limitations that should be considered in clinical interpretation. Most of the included studies were single-center with relatively small samples, and many did not adequately implement blinding and allocation concealment, potentially introducing bias. Heterogeneity among studies was considerable for some outcomes, reflecting differences in study populations, treatment protocols, and assessment criteria. In addition, long-term follow-up was limited, preventing conclusions about the durability of therapeutic effects.

Future studies should address these limitations through multicenter trials with larger samples, standardized protocols, and prolonged follow-up to confirm the sustained efficacy of acupuncture in the treatment of endometriosis.