Alternative therapies are frequently used to relieve various symptoms of patients. They are used instead of standard medical treatments and alternative therapies are distinct from complementary medicine which is meant to accompany, not to replace, standard medical practices. Alternative therapies can include various well-known treatments such as acupressure, acupuncture, massage, aromatherapy, diet, and herbal medicine [
Pain occurs in up to 70% of patients with advanced cancer and about 65% of patients dying of nonmalignant disease [
Aromatherapy has been used in various diseases [
We searched the potential relevant publications between 1 January 1990 and 31 July 2015 on PubMed and Cochrane library; the search strategy was “(aromatherapy OR essential oil) AND (pain OR ache) AND (cancer OR tumor OR carcinoma)” without limitations for language.
Studies were included if they met the following inclusion criteria: (1) the study design was randomized controlled trial, (2) the subjects were human, (3) the experimental group received massage with essential oil and the control group received usual care only, and (4) mean difference and standard deviation were reported in the article. The components of essential oil and the spices of cancer were not discussed here. The title or abstract of all publications which were similar to the outcome was reviewed to evaluate whether to include them or not. The full texts were checked carefully to see if there was any potentially related information.
The following data were extracted from included eligible studies through a data extraction form: first author, year of publication, country of publication, study period, assigned group, randomly assigned participants, types of participants, component of essential oil, intervention time, and methods used for assessing the intensity of pain. Furthermore, we used the Cochrane Collaboration tool to assess the risk of bias of the included trials and evaluated the following 7 domains associated with bias of intervention: random sequence generation, allocation concealment, blinding of participant and personnel, blinding of outcome assessment, incomplete outcome data (Attrition bias: it refers to systematic differences between groups in withdrawals from a study lead to incomplete outcome data. Exclusions refer to situations in which some subjects are omitted from reports of analyses, despite outcome data being available to the trial lists.), selective reporting, and other biases (bias due to problems not covered elsewhere).
The Review Manager 5.3 (The Nordic Cochrane Centre, The Cochrane Collaboration, 2014) was used for meta-analysis. We presented the mean difference (MD) or standardized MD with 95% confidence interval (CI) for continuous data. Because the baseline which assesses the intensity of pain was different, we used standardized data to adjust the different baseline. Heterogeneity in meta-analysis refers to the variation in study outcomes between studies. In this study, we used
Figure
PRISMA (preferred reporting items for systematic reviews and meta-analyses) flow diagram.
The characteristics of the included trials are summarized in Table
Characteristics of included randomized controlled trials.
Author | Publication |
Country | Study |
Assigned |
Randomly assigned participants ( |
Types of participants | Component of essential oil | Intervention time | Methods used for assessing pain intensity |
---|---|---|---|---|---|---|---|---|---|
Wilkinson et al. [ |
2007 | UK | 1998–2002 | Control: usual care |
115 |
Patients with any type of cancer | Unclear | 10 weeks | EORTC (European Organisation for Research and Treatment of Cancer) |
|
|||||||||
Wilkie et al. [ |
2000 | USA | 1995-1996 | Control: usual care |
14 |
Patients with any type of cancer | Unclear | 2 weeks | PAT (Pain Assessment Tool) |
|
|||||||||
S. P. Weinrich and M. C. Weinrich [ |
1990 | USA | Unclear | Control: no physical contact |
14 |
Patients with any type of cancer | Unclear | 10 minutes | VAS (Visual Analogue Scale) |
Risk of bias summary: authors’ judgements about each risk of bias item for each included study.
We pooled the data from the included trials using the fixed-effect model because of no heterogeneity (chi-square value = 0.52,
Meta-analysis based on the mean difference between massage with essential oil and usual care.
Publication bias was defined as the publication or nonpublication of studies depending on the direction and statistical significance of the results, and the first systematic investigations of publication bias focused on this aspect of the problem. As Figure
Funnel plot based on Wilkie et al., S. P. Weinrich and M. C. Weinrich, and Wilkinson et al.
The popularity of complementary and alternative medicine (CAM) is growing among the general public, and, in many developed countries, its use varies from 70% to 80% [
Aromatherapy encompasses the use of essential oils derived from different types of plant sources for a variety of application methods [
Systematic reviews and meta-analysis aim to collate and synthesise all studies that meet prespecified eligibility criteria using methods that attempt to minimize bias [
From the methodological viewpoint, there were still several limitations in this meta-analysis. The major one was the fact that the amount of trials which could be searched was too insufficient and the statistical power could be lower due to smaller sample sizes. Nevertheless, the serious bias in this meta-analysis was publication bias; in the overall meta-analysis of randomized controlled trials there was no significant on the publication bias (test for overall effect:
In conclusion, our data did not suggest that aromatherapy massage may be effective in reducing pain for the cancer patients. We also cannot completely elucidate the nonspecific effects of aromatherapy. Further randomized studies should include more objective measures to explain the possible mechanism of reduction in pain due to cancer.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Ting-Hao Chen and Tao-Hsin Tung contributed equally to this study.
This study was supported in part by the Ministry of Science and Technology (MOST-104-2511-S-182-004).