Regional Anesthesia-Analgesia

Targeting the mu-Opioid Receptor for Cancer Treatment

PURPOSE OF REVIEW

Opioids are still the most effective and widely used treatments for acute and chronic pain in cancer patients. This review focuses on the impact of opioids and mu-opioid receptors (MOR) on tumor progression and providing new ideas for targeting the MOR in cancer treatment.

RECENT FINDINGS

Studies estimated that opioids facilitate tumor progression and are related to the worse prognosis in cancer patients. As the primary receptor of opioids, MOR is involved in the regulation of malignant transformation of tumors and participating in proliferation, invasion, metastasis, and angiogenesis. MOR may be a new molecular marker of malignant tumors and thus become a new target for cancer therapy, which may be beneficial to the outcomes of cancer patients.

Paravertebral anaesthesia with or without sedation versus general anaesthesia for women undergoing breast cancer surgery

BACKGROUND

Breast cancer is one of the most common cancers among women. Surgical removal of the cancer is the mainstay of treatment; however, tumour handling during surgery can cause microscopic dissemination of tumour cells and disease recurrence. The body's hormonal response to surgery (stress response) and general anaesthesia may suppress immunity, promoting tumour dissemination. Paravertebral anaesthesia numbs the site of surgery, provides good analgesia, and blunts the stress response, minimising the need for general anaesthesia.

OBJECTIVES

To assess the effects of paravertebral anaesthesia with or without sedation compared to general anaesthesia in women undergoing breast cancer surgery, with important outcomes of quality of recovery, postoperative pain at rest, and mortality.

SEARCH METHODS

On 6 April 2020, we searched the Specialised Register of the Cochrane Breast Cancer Group (CBCG); CENTRAL (latest issue), in the Cochrane Library; MEDLINE (via OvidSP); Embase (via OvidSP); the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal; and ClinicalTrials.gov for all prospectively registered and ongoing trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) conducted in adult women undergoing breast cancer surgery in which paravertebral anaesthesia with or without sedation was compared to general anaesthesia. We did not include studies in which paravertebral anaesthesia was given as an adjunct to general anaesthesia and then this was compared to use of general anaesthesia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted details of trial methods and outcome data from eligible trials. When data could be pooled, analyses were performed on an intention-to-treat basis, and the random-effects model was used if there was heterogeneity. When data could not be pooled, the synthesis without meta-analysis (SWiM) approach was applied. The GRADE approach was used to assess the certainty of evidence for each outcome.

MAIN RESULTS

Nine studies (614 participants) were included in the review. All were RCTs of parallel design, wherein female patients aged > 18 years underwent breast cancer surgery under paravertebral anaesthesia or general anaesthesia. None of the studies assessed quality of recovery in the first three postoperative days using a validated questionnaire; most assessed factors affecting quality of recovery such as postoperative analgesic use, postoperative nausea and vomiting (PONV), hospital stay, ambulation, and patient satisfaction. Paravertebral anaesthesia may reduce the 24-hour postoperative analgesic requirement (odds ratio (OR) 0.07, 95% confidence interval (CI) 0.01 to 0.34; 5 studies, 305 participants; low-certainty evidence) compared to general anaesthesia. Heterogeneity (I² = 70%) was attributed to the fixed dose of opioids and non-steroidal analgesics administered postoperatively in one study (70 participants), masking a difference in analgesic requirements between groups. Paravertebral anaesthesia probably reduces the incidence of PONV (OR 0.16, 95% CI 0.08 to 0.30; 6 studies, 324 participants; moderate-certainty evidence), probably results in a shorter hospital stay (mean difference (MD) -79.39 minutes, 95% CI -107.38 to -51.40; 3 studies, 174 participants; moderate-certainty evidence), and probably reduces time to ambulation compared to general anaesthesia (SWiM analysis): percentages indicate vote counting based on direction of effect (100%, 95% CI 51.01% to 100%; P = 0.125; 4 studies, 375 participants; moderate-certainty evidence). Paravertebral anaesthesia probably results in higher patient satisfaction (MD 5.52 points, 95% CI 1.30 to 9.75; 3 studies, 129 participants; moderate-certainty evidence) on a 0 to 100 scale 24 hours postoperatively compared to general anaesthesia. Postoperative pain at rest and on movement was assessed at 2, 6, and 24 postoperative hours on a 0 to 10 visual analogue scale (VAS). Four studies (224 participants) found that paravertebral anaesthesia as compared to general anaesthesia probably reduced pain at 2 postoperative hours (MD -2.95, 95% CI -3.37 to -2.54; moderate-certainty evidence). Five studies (324 participants) found that paravertebral anaesthesia may reduce pain at rest at 6 hours postoperatively (MD -1.54, 95% CI -3.20 to 0.11; low-certainty evidence). Five studies (278 participants) found that paravertebral anaesthesia may reduce pain at rest at 24 hours postoperatively (MD -1.19, 95% CI -2.27 to -0.10; low-certainty evidence). Differences in the methods of two studies (119 participants) and addition of clonidine to the local anaesthetic in two studies (109 participants), respectively, contributed to the heterogeneity (I² = 96%) observed for these two outcomes. Two studies (130 participants) found that paravertebral anaesthesia may reduce pain on movement at 6 hours (MD-2.57, 95% CI -3.97 to -1.17) and at 24 hours (MD -2.12, 95% CI -4.80 to 0.55; low-certainty evidence). Heterogeneity (I² = 96%) was observed for both outcomes and could be due to methodological differences between studies. None of the studies reported mortality related to the anaesthetic technique. Eight studies (574 participants) evaluated adverse outcomes with paravertebral anaesthesia: epidural spread (0.7%), minor bleeding (1.4%), pleural puncture not associated with pneumothorax (0.3%), and Horner's syndrome (7.1%). These complications were self-limiting and resolved without treatment. No data are available on disease-free survival, chronic pain, and quality of life. Blinding of personnel or participants was not possible in any study, as a regional anaesthetic technique was compared to general anaesthesia. Risk of bias was judged to be serious, as seven studies had concerns of selection bias and three of detection bias.

AUTHORS' CONCLUSIONS

Moderate-certainty evidence shows that paravertebral anaesthesia probably reduces PONV, hospital stay, postoperative pain (at 2 hours), and time to ambulation and results in greater patient satisfaction on the first postoperative day compared to general anaesthesia. Paravertebral anaesthesia may also reduce postoperative analgesic use and postoperative pain at 6 and 24 hours at rest and on movement based on low-certainty evidence. However, RCTs using validated questionnaires are needed to confirm these results. Adverse events observed with paravertebral anaesthesia are rare.

Does Opioid Use Cause Angiogenesis and Metastasis?

Objective

To provide a comprehensive overview of the potential for morphine to lead to angiogenesis and metastasis.

Background

Morphine is often the treatment of choice for severe cancer-related pain. Small studies have been emerging that indicate that opioids may influence angiogenesis and metastasis, but this has not yet been comprehensively synthesized.

Purpose

To highlight morphine's relationship with angiogenesis and metastasis in in vitro models.

Method

A review of the literature was conducted using PubMed (1966 to 2015) and Cochrane Library (1987 to 2015) electronic databases. The search, as well as consultation with experts, yielded 84 articles for initial review, 12 of which met inclusion for review. Possible theories of the underlying etiology of the metastasis and angiogenesis were recorded.

Results

All studies were assessed using the PRISMA checklist.

Conclusion

This systematic review demonstrates that morphine has a potential causal relationship with angiogenesis and metastasis. This is likely due to multiple etiologies, including immunosuppressive, pro-inflammatory, and pro-angiogenetic.

The Relationship Between Regional Anesthesia and Cancer: A Metaanalysis

BACKGROUND

Some studies have suggested using epidural analgesia after cancer surgery to reduce metastasis. This article examines the relationship between regional anesthesia (RA) and cancer metastasis in an array of cancers.

METHODS

We conducted a review of the literature using PubMed and included 67,577 patients across 28 studies in a metaanalysis, evaluating the hazard ratios (HRs) of overall survival, recurrence-free survival, and biochemical recurrence-free survival.

RESULTS

We found no benefit to RA as it relates to cancer. The HR was 0.92 for overall survival, 1.06 for recurrence-free survival, and 1.05 for biochemical recurrence-free survival. Despite the overall analysis showing no benefit, we found some benefit when we evaluated only the randomized trials. However, we found no significant benefit of RA when we evaluated the cancers (gastrointestinal, prostate, breast, and ovarian) individually.

CONCLUSION

This metaanalysis shows that RA has no overall survival, recurrence-free survival, or biochemical recurrence-free survival benefit. However, some individual studies have shown significant benefit in terms of cancer recurrence. Further, RA reduces the use of opioids, which has led to some secondary benefits. Further studies are needed to establish the benefits of RA as it relates to cancer.