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How Many Cancer Patients Use Complementary and Alternative Medicine: A Systematic Review and Metaanalysis Markus Horneber, Gerd Bueschel, Gabriele Dennert, Danuta Less, Erik Ritter and Marcel Zwahlen Integr Cancer Ther published online 21 October 2011 DOI: 10.1177/1534735411423920 The online version of this article can be found at: http://ict.sagepub.com/content/early/2011/10/15/1534735411423920

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Review Article

How Many Cancer Patients Use Complementary and Alternative Medicine: A Systematic Review and Metaanalysis

Integrative Cancer Therapies XX(X) 1–17 © The Author(s) 2011 Reprints and permission: http://www. sagepub.com/journalsPermissions.nav DOI: 10.1177/1534735411423920 http://ict.sagepub.com

Markus Horneber, MD1, Gerd Bueschel, MD2, Gabriele Dennert, MD, MPH1, Danuta Less, MD3, Erik Ritter, MD1, and Marcel Zwahlen, PhD, MSc4

Abstract Background. No comprehensive systematic review has been published since 1998 about the frequency with which cancer patients use complementary and alternative medicine (CAM). Methods. MEDLINE, AMED, and Embase databases were searched for surveys published until January 2009. Surveys conducted in Australia, Canada, Europe, New Zealand, and the United States with at least 100 adult cancer patients were included. Detailed information on methods and results was independently extracted by 2 reviewers. Methodological quality was assessed using a criteria list developed according to the STROBE guideline. Exploratory random effects metaanalysis and metaregression were applied. Results. Studies from 18 countries (152; >65 000 cancer patients) were included. Heterogeneity of CAM use was high and to some extent explained by differences in survey methods. The combined prevalence for “current use” of CAM across all studies was 40%. The highest was in the United States and the lowest in Italy and the Netherlands. Metaanalysis suggested an increase in CAM use from an estimated 25% in the 1970s and 1980s to more than 32% in the 1990s and to 49% after 2000. Conclusions. The overall prevalence of CAM use found was lower than often claimed. However, there was some evidence that the use has increased considerably over the past years. Therefore, the health care systems ought to implement clear strategies of how to deal with this. To improve the validity and reporting of future surveys, the authors suggest criteria for methodological quality that should be fulfilled and reporting standards that should be required. Keywords complementary therapies, complementary and alternative medicine, systematic review, prevalence, alternative medicine, CAM use, cancer

Introduction and Objectives Consistent and topical information about the frequency and patterns of use of complementary and alternative medicine (CAM) in cancer patients is essential to assess its implications for oncological care as well as to develop evidencebased concepts for research that have the potential to inform continuing education and regulation in the CAM field.1-4 However, the only review that attempted to systematically summarize data on the prevalence of CAM use in cancer patients was published in 1998 and included 26 surveys of cancer patients, either adults or children, from 13 countries and found an average prevalence of CAM use of 31%, with rates ranging from 14% up to 64%. The wide range of prevalence of CAM use was not explained by variation among countries or change over time; in fact, the authors concluded that methodological factors like lack of specificity

and inconsistent definitions of CAM, possible selection and recall bias, and the lack of a standardized series of questions were the reasons for the heterogeneity in the prevalence estimates.5 Since the publication of this systematic review, a large number of surveys on the use of CAM in cancer patients have been published. Although many reports and

1

Klinikum Nuernberg, Nuernberg, Germany Vivantes Klinikum Neukoelln, Berlin, Germany 3 St Marien-Hospital, Hagen, Germany 4 University of Bern, Bern, Switzerland 2

Corresponding Author: Markus Horneber, Department of Internal Medicine, Division of Oncology/Hematology, Klinikum Nuernberg, Ernst-Nathan Str 1, D-90419 Nuernberg, Germany Email: [email protected]


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narrative reviews from these survey data alleged an increase in the prevalence of CAM use in cancer patients over the past years6-11 and considerable differences among European countries,12 a comprehensive review that systematically summarizes and appraises this literature is absent. Therefore, we felt the need to provide a systematic and critical review on the use of CAM in cancer patients and to offer recommendations for future research. Our systematic review addresses several research questions: • How many patients with cancer use CAM? • Which factors contribute to the variation in prevalence rates of CAM use? • Do the prevalence rates of CAM use change over time? • Are there differences in prevalence rates among countries or continents? • To what extent are prevalence rates influenced by survey methods?

Methods For the purpose of this review, we decided to adopt CAM as an acronym but would like to alert the readers to be vigilant because the definition of this term and the underlying treatment options vary greatly in the surveys under investigation. Furthermore, we applied the term prevalence of CAM use in this review not in the strict epidemiological sense but for the proportion of people who had used CAM therapies at the time of the individual survey or over a preceding period of time.

Literature Search and Eligibility Criteria We searched MEDLINE (1966 to January 2009), AMED (1985 to January 2009), and Embase (1991 to January 2009) and the bibliographies of all located articles and the authors’ own files. Search terms included subject heading terms (eg, complementary therapies; medicine, traditional; questionnaires; health behavior) along with a large number of free text terms (eg, cancer, complementary medicine, alternative medicine, unorthodox medicine, unproven, unconventional, surveys, or interview). The results were then combined with subject heading cancer terms (eg, neoplasms or cancer). All studies were checked for double publications. To be included in this review, surveys had to report original data of at least 100 adult cancer patients from the following countries: Australia, Canada, all European countries (including Israel and Turkey), New Zealand, and the United States (including Hawaii). Only quantitative survey data assessing how many cancer patients used CAM were included in this review. Surveys restricting their definition to a single CAM treatment, published only in abstract form, and conducted at

study sites that predominantly offer CAM were excluded. No language restrictions were made.

Data Extraction and Assessment Data on survey methods, participants, procedures, and results were extracted by means of a predefined comprehensive extraction form and independently by 2 reviewers. Data from articles in languages other than German and English were extracted with the help of a native speaker. A criteria list for assessment of methodological quality was developed and amended during the review process according to the STROBE guideline and another guideline published by Kelley et al.13,14 The list comprised 4 categories (sampling, participants, procedures of data collection, and outcomes), with 16 items in all. All discrepancies were solved through discussion among the reviewers. Instead of using arbitrary measures of quality (ie, quality scores), the actual effect of key methodological characteristics on results was tested. Extracted study data were entered into a relational database management system (MS Access 2000) and double-checked for entry errors.

Data Synthesis To compare data, surveys were grouped into (1) 3 continents— Australia/NZ (surveys from Australia and New Zealand), Europe (ie, surveys from all European countries including Israel and Turkey), and North America (surveys from Canada and the United States, including Hawaii); (2) 5 European regions—Benelux (surveys from the Netherlands), German-speaking (Austria, Germany, and Switzerland), Great Britain (United Kingdom), Mediterranean (France, Israel, Italy, Spain, and Turkey), and Scandinavia (Denmark, Sweden, and Norway); (3) 3 periods in which surveys were conducted—65% Information on NP/NRb Survey design Longitudinal assessment Data collection Interview Questionnaire Effectivenessc Trainingd Preteste CAM list presentedf Time recalls of CAM use Point in timeg Time period Similarh Varyingi

Overall (152)

North America (65)

Australia/NZ (13)

Europe (74)

5% (7) 8% (12) 88% (133) 19% (29) 73% (111) 24% (37) 48% (73) 36% (54) 5% (7)

23% (3) — 77% (10)

6% (4) 15% (10) 78% (51)

— 3% (2) 97% (72)

23% (3) 38% (5)

31% (20) 75% (49)

8% (6) 77% (57)

15% (2) 38% (5) 31% (4)

32% (21) 52% (34) 43% (28)

19% (14) 46% (34) 30% (22)

15% (2)

5% (3)

3% (2)

35% (53) 66% (99)

23% (3) 77% (10)

38% (25) 62% (40)

34% (25) 66% (49)

25% (13) 36% (36) 45% (69) 26% (40)

33% (1) 40% (4) 31% (4)

28% (7) 40% (16) 68% (44)

20% (5) 33% (16) 28% (21)

46% (6)

23% (15)

26% (19)

13% (20) 67% (102)

23% (3) 54% (7)

18% (12) 58% (38)

7% (5) 77% (57)

Abbreviations: NZ, New Zealand; NP, nonparticipants; NR, nonreponders; CAM, complementary and alternative medicine. a Hospitals, practices, and local registries. b At least basic information on NP and/or NR. c Proportions in these rows were calculated using the number of surveys in which data collection were done with interviews or questionnaires as denominators. d Training of interviewers reported. e Pilot testing of questionnaire reported. f Participants were provided with predefined checklists of CAM therapies. g At the time of the survey (ie, current use). h During previous 3/6/12 months. i Since diagnosis/unclear period of time/not reported.

prevalences of CAM use was not significant (P = .40 from metaregression). However, in 8 surveys, the percentage of patients “currently using CAM” was contrasted with the percentage of patients who had used it in the past. All point prevalences of CAM use in these surveys were lower (29%; 95% CI = 12%-45%) than the respective period prevalences (41%; 95% CI = 20%-63%).25,28,64,79,80,101,137,142 The difference in proportion in these studies was estimated at 11% (95% CI = 7%-15%; P < .001). Three authors compared the use of CAM during different time periods: Paltiel et al74 found that 35% of patients used CAM during 3 months prior to the survey, whereas

51% had used it since their cancer diagnosis. Rees et al110 reported a difference of 10% in the prevalence of CAM use when the recall period spanned 12 months (22%) compared with when the recall related to the time period since the cancer was diagnosed (32%), which spanned a mean of 4.4 years. Shakeel et al117 found a difference of 24% in the prevalence rates of CAM use when the recall period spanned 12 months (26%) compared with when the recall related to the lifetime period (50%). International differences in CAM use. There were considerable differences between countries in the pooled proportions of patients using CAM (Figure 2), with the highest


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Figure 2. Forrest plot of period prevalence of complementary and alternative medicine use in different countries: diamonds show the pooled estimates and their 95% confidence intervals, vertical dotted line shows the pooled weighted estimate

Figure 3. Forrest plot of period prevalence of complementary and alternative medicine use in different European regions: diamonds show the pooled estimates and their 95% confidence intervals, vertical dotted line shows the pooled weighted estimate

Table 3. Pooled Prevalences of CAM Use by Continents

Table 4. Pooled Prevalences of CAM Use by Periods of Data Collectiona

Point Prevalence

Period Prevalence

Continent

Meana

95% CIa

nb

Mean

95% CI

n

Europe Australia/NZ North America

34%c 40% 46%

25%-44% 13%-67% 35%-56%

19 5 15

37%d 43% 50%

33%-41% 19%-67% 41%-58%

58 8 50

Abbreviations: CAM, complementary and alternative medicine; CI, confidence interval. a Estimated using a random effects model.15 b Number of studies included in metaanalysis. c P = .29 from metaregression for the comparison of Europe versus North America. d P < .01 from metaregression for the comparison of Europe versus North America.

proportions in the United States (50%; 95% CI = 40%-60%; n = 36) and the lowest in Italy (22%; 95% CI = 10%-35%, n = 2) and the Netherlands (22%; 95% CI = 9%-37%, n = 2). Grouped into continents, pooled proportions were higher in North America compared with Australia/NZ or Europe (Table 3). The 13% difference in the period prevalence of CAM use between North America and Europe was statistically significant (P < .01; Table 3). Within North America, there was only a small difference in the proportions of CAM users between surveys from Canada and those from the United States (Figure 2). In contrast, large differences were found among European countries, with the highest prevalence of CAM use in Turkey (48%; 95% CI = 39%-57%; n = 10; Figure 2). When European countries were grouped into 5 regions, the highest prevalence of CAM use was found in German-speaking countries (41%; 95% CI = 35%47%; n = 25; Figure 3).

Period of Data Collection