Between 9 and 81% of cancer patients are said to use at least one type of complementary or alternative therapy after their cancer diagnosis (Ernst, 2000; Catt et al, 2006). In particular, self-medication with herbal medicines and other ‘natural’ substances is widespread and increasing in the United Kingdom (Werneke et al, 2004a; Astin et al, 2006). It has been estimated that a large proportion of patients with cancer use herbal medicines. These may be taken to prevent or relieve some of the symptoms of the cancer itself (Ali and Hussain-Gambles, 2005); to help alleviate some of the side effects from cancer treatments, such as radiotherapy or chemotherapy (Vickers et al, 2006); to treat an associated condition, such as anxiety or depression, or to provide a sense of control or a feeling of active involvement in cancer treatment (Verhoef et al, 1999). However, estimates of the prevalence of herbal medicine use are inconsistent (varying from 3 to 25% of cancer patients), and the quality and scope of existing studies are limited (Ernst and Cassileth, 1998; Gratus et al, 2009a). Research typically focuses on restricted patient cohorts and specific tumour sites; includes small numbers of participants, and uses heterogeneous methodologies and definitions of herbal medicines, which make it difficult to assess the precise extent of herbal medicine use by cancer patients (Crocetti et al, 1998). Herbal medicines are also frequently subsumed under the broader heading of complementary and alternative medicines, and their use assessed alongside other therapies, such as aromatherapy, reflexology, meditation, acupuncture, and homeopathy (Downer et al, 1994; Corner et al, 2006).

Among cancer patients, users of herbal medicines tend to be female, younger, and have higher socioeconomic status than non-users (Harris et al, 2003). Disease-related factors, such as the type of cancer, stage of disease, and disease duration have also been found to be significant predictors of herbal medicine use (Miller et al, 1998), with women with breast cancer most likely to use herbal medicines in comparison with the general population, and compared with those with other cancer types (Morris et al, 2000). However, studies of breast cancer patients and herbal medicine use constitute the majority of research literature, and may not be representative of other cancer diagnostic groups (Molassiotis et al, 2005).

Alongside increased interest in the use of herbal medicines by people with cancer, there has been a rise in concern about the safety of these treatments (Balneaves et al, 1999). Herbal medicines are often seen as more natural, and therefore safer than conventional treatments, and it is generally believed that they carry little potential for harm (Corner et al, 2006; Vickers et al, 2006). However, in some cases, herbal medicines can present significant risks (Gratus et al, 2009a, 2009b). They may affect adherence with prescribed treatments, cause harmful interactions with conventional medications, reduce treatment efficacy, or lead to adverse events (Frye et al, 2004; Catt et al, 2006; Medicines and Healthcare Products Regulatory Agency, 2007). A recent systematic review of herbal medicine use by cancer patients identified 21 case reports of toxic effects and adverse events in users of herbal medicines (Olaku and White, 2010). As a result of the possibility of interactions between herbal medicines and conventional treatments, people with cancer are encouraged to advise health-care professionals if they are taking any type of medication, including herbal medicines and other supplements (Cancer Backup, 2010), although studies suggest that few patients do so (Corner et al, 2006).

Given the potential risks, and the lack of data to substantiate the use of herbal medicines by cancer patients in the United Kingdom, there is a need to better understand the prevalence of herbal medicine use among cancer patients, as well as improving knowledge of which herbal medicines patients use. This is an important first step in the development of accessible, authoritative, and independent information resources about herbal medicines and cancer, which are currently lacking in the United Kingdom (Gratus et al, 2009b). The aim of this study was to investigate the prevalence of herbal medicine use among people with cancer in the West Midlands, and to determine the sociodemographic and cancer-related characteristics that may predict herbal medicine use within this group.

Study design and setting

This study used a cross-sectional survey, distributed by post, to oncology patients being followed up at University Hospitals Coventry and Warwickshire NHS Trust (UHC&W).

Participants and recruitment

Subsequent to securing permission from consultants responsible for the care of patients, the hospital information system was interrogated to identify a sample of eligible patients aged 18 and over, at least 6 months and no >5 years after a diagnosis of invasive cancer (between 1 April 2004 and 30 June 2009), who had been treated with curative intent. A total of 1507 potential participants were identified. The responsible consultant examined the list of potential participants to verify that the patient had been treated for invasive cancer and had been diagnosed within the specified time frame. Patients known to be terminally ill, or whom the consultant believed may be distressed by receipt of the survey for any other reason, were excluded from the sample to minimise the possibility of distress, as were any individuals whose records did not indicate a consultant; duplicate records; those for whom a valid postal address could not be identified, and those who had died in the period between sample identification and survey mailing.

After exclusions had been made, 1498 eligible patients were sent a letter of invitation, a patient information sheet and a survey, to be returned to the research team at University of Birmingham via a FREEPOST envelope, also enclosed. This sample size assumed a prevalence of herbal medicine use among cancer patients of between 7 (Corner et al, 2006) and 13% (Harrison et al, 2004), and that a 60% response rate would yield 900 responses. This sample would be of sufficient size to determine the overall prevalence of herbal medicine use among respondents with a precision of 2% (95% confidence interval). Survey recipients who had not responded to the initial mailing after 2 weeks received one reminder.

Survey

Survey content was informed by the findings of a systematic review of the literature relating to herbal medicine use by cancer patients in the United Kingdom (Gratus et al, 2009a). The survey included closed questions on sociodemographic characteristics (age, gender, and ethnicity), cancer-related characteristics (year of diagnosis), and a number of categorical (yes/no response) questions relating to the use of herbal medicines, vitamin/mineral supplements and homeopathic remedies; the sources through which herbal medicines were obtained by users (e.g., bought on the high street, from a herbal medicine practitioner, purchased via the Internet), and the use of specific herbal medicines since diagnosis, detailed in a pre-coded ‘tick-list’, derived from a review of the most commonly cited herbal medicines from existing research literature. Patients were able to select multiple herbal medicines if they had used more than one. They were also able to list any additional herbal medicines that they had used since diagnosis, which were not included in the pre-coded list, using a free-text response box.

Data analysis

Analysis focused on the sociodemographic and cancer-related characteristics of respondents, and their association with herbal medicine use. In addition to the data obtained from respondents via their survey responses, anonymised hospital records for each respondent were used to derive information related to cancer type, classified according to International Classification of Diseases (ICD-10) categories for invasive cancer (World Health Organization, 1994), and postcode data were used to derive a deprivation score, which was converted into a deprivation quartile using the 2007 Indices of Multiple Deprivation: quartile 1=most affluent; quartile 4=most deprived (Department of Communities and Local Government, 2007).

An individual was defined as a herbal medicine user if they answered ‘yes’ to the question: ‘have you used herbal remedies since your cancer was diagnosed?’ and/or gave a positive response to any question asking about herbal medicine purchasing, and/or indicated the use of a specific herbal medicine from the pre-coded list or via the free-text response box. Free-text responses were coded and analysed in the same way as herbal medicines indicated in the tick-list. Chi-squared tests and binary logistic regression were used to compute bivariate and multivariate odds ratios (ORs) to evaluate the association between sociodemographic and cancer-related characteristics and herbal medicine use, and to assess the factors predictive of herbal medicine use by patients with cancer. In order to test for responder bias, age, gender, ethnicity, deprivation, and time since diagnosis distributions for respondents and non-respondents were compared using χ2 tests. Prevalence rates of herbal medicine use were age and gender standardised to the cancer patient population in England using the 2006 cancer registration statistics (Office for National Statistics, 2006). All data were analysed using SPSS (version 15.0, SPSS Inc., Chicago, IL, USA).

Validation data set

As the survey population was identified from the records of one hospital only, the survey was repeated on a smaller scale at another hospital in Birmingham (541 patients mailed), in order to validate the rates of herbal medicine use identified from survey respondents treated at UHC&W and assess the wider generalisability of the findings. Patients were identified at the participating hospital in Birmingham in the same way as for the larger survey, according to the same eligibility criteria, and received the same survey and study literature; however, non-responders did not receive a reminder.

Of 1498 surveys distributed, 27 (1.8%) were returned blank, indicating that the recipient did not wish to receive a reminder. A further 337 survey recipients (22.5%) did not respond to either the initial or reminder mailings, giving a total of 1134 useable responses (response rate 75.7%), Figure 1.