Journal of the New Zealand Medical Association, 08-June-2012, Vol 125 No 1356
Dietary information for colorectal cancer survivors: an unmet need
Jessie M Pullar, Alexandra Chisholm, Christopher Jackson
Colorectal cancer (CRC) is New Zealand’s second most common cancer with over 2800 new cases registered each year and over 1200 deaths annually.1 Despite a reduction in incidence, there are an increasing number of individuals affected due to an aging population.2
Epidemiological studies have underscored the importance of diet on colorectal cancer risk.3 In addition to obesity4 and diabetes mellitus5,6 being risk factors, individual food groups confer risk, such as red, processed or well-cooked meat7,8 as well as refined sugars and cereals;9 on the other hand, vegetables and fibre are thought to be protective.10
These studies demonstrate an association between the development of colorectal cancer and dietary patterns. However colorectal carcinogenesis is thought to be a multi-step process,11 with “hits” occurring over several years and most CRC recurrences occur within 3 years of surgery.12 Therefore simply because long-term dietary patterns can induce carcinogenesis, it does not necessarily follow that dietary change can reduce risk of CRC recurrence.
Two pivotal studies have demonstrated that there is a relationship between dietary patterns and risk of recurrence following definitive cancer treatment, suggesting a role for dietary intervention as an adjunctive treatment. An observational study embedded within an adjuvant trial for stage 3 colon cancer examined dietary patterns and the risk of CRC relapse.13 1009 patients were recruited.
Researchers used previously validated food frequency questionnaires (FFQ) to determine two distinct dietary patterns which participants followed to a varying extent. These included the Western diet: high in red/processed meat, high fat dairy products, refined carbohydrates; and the prudent diet: high in fish, poultry, fruits and vegetables.
Participants in the highest quintile of western diet intake experienced significantly worse disease free survival, compared to those in the lowest quintile for recurrence or death from any cause (HR: 3.25 [95 % CI:2.04–5.19, p<0.00]), as well as a higher rate of disease recurrence (HR 2.85, [95 % CI 1.75–4.63,p<0.001]).
Adherence to a prudent dietary pattern showed no significant association with outcome measures during the course of the study, regardless of intake quintile (HR 1.20 [95 % CI 0.83–1.75, p=0.78]). Results were not significantly affected by participant’s age, sex, nodal status, BMI, physical activity, total energy intake or chemotherapy treatment group.
The US Polyp Prevention Trial (USPPT) aimed to establish a relationship between dietary patterns and adenoma formation. Participants with a history of large bowel adenomatous polyps were randomised into intervention (n=1037) or control group (n=1042). The intervention group received dietary advice and set three dietary goals: to limit fat intake to 20% of total energy intake, consume at least 4.30g/megajoule (MJ) of dietary fibre and to consume at least 0.84 servings of fruit or vegetables per MJ/day.
Participants received colonoscopies at year 1 and 4 following randomisation to allow detection of colorectal adenomas. An annually administered FFQ was used to evaluate the number of goals patients reached each year. The maximum number of goals was 12 (three goals per year over 4 years). The study was negative for its primary endpoint, failing to show that dietary intervention could reduce polyp formation. 14 However subgroup analysis identified those participants classed as ‘super compliers’ (who meet between 9–12 goals) to the dietary intervention had a 35% lower incidence of colorectal adenoma recurrence (OR=0.65, 95 % CI: 0.47–0.92).15
Based on the observational evidence that diet remains associated with risk of cancer recurrence, and that cancer survivors are highly motivated to undertake dietary change,16 we undertook a project aiming to establish the dietary patterns of colorectal cancer patients in our region, the level of dietary advice they currently received and its impact on their behaviour. We utilised this information to develop a resource of dietary advice based on the findings of the Meyerhardt study.
Study design—We surveyed a convenience sample of patients diagnosed with colorectal cancer who were currently on treatment or undergoing follow-up in surgical or medical oncology clinics at the Southern District Health Board (Dunedin and Invercargill, New Zealand) during April to June 2010. The study received expedited review from the Lower South Regional Ethics Committee. Patients were approached by their doctor or nurse at outpatient attendances, and the study administered by a Dietetics Student (JP).
Inclusion criteria were patients with a diagnosis of CRC (stage II, III or IV), aged 18 or over, with sufficient literacy to comprehend the questionnaire. Exclusion criteria included cancer of the appendix (n=1). All patients provided written informed consent. An original (non-validated) 16-point questionnaire was developed and then tested for comprehension and readability on 3 patients prior to formal commencement of the study, with no amendments deemed necessary by researchers or participants. Demographic information and cancer information was retrieved from the clinical record.
Outcome measures—The outcome measures were participants’ perceived level of dietary information received, how this information met their needs, whether they would be interested in additional dietary information, if they would consider changing their diet based on this and in which format they would like to receive this information. Participants were also asked to use a Likert scale to estimate the extent to which diet influenced the risk of cancer recurrence.
Dietary pattern—A simplistic measure of patients dietary pattern was used which involved participants choosing between a dietary pattern which was typically high in Western foods or prudent foods as defined by Meyerhardt et al.13 This measured participant’s subjective perception of their general diet pre and post diagnosis and was not a validated measure of dietary pattern.
BMI category—Participants BMI was calculated by dividing their weight (kg) by their height (m) squared. The World Health Organization (WHO) BMI categories were used to classify participants as underweight (<18.5 kg/m2), healthy weight (18.5–24.99 kg/m2), overweight (25–29.99 kg/m2) or obese (≥30 kg/m2)17.
Data analysis—Participants were categorised according to their geographic location (Otago or Southland), BMI value and stoma status. Questionnaire responses were assessed in relation to these groupings. Percentages were calculated to compare responses and characteristics between groups. Data analysis was performed using Microsoft Excel 2007 and STATA I/C 12 for MacIntosh software.
A total of 40 participants were recruited. Patient demographics are described in Table 1. Fifty-two percent of participants reported making dietary changes due to their condition or treatment, whilst 32.5% received advice on dietary change. The most frequent source of dietary advice was a dietitian, or friend/family member. No patients reported receiving dietary information from doctors or nurses. No patients felt they had received too much dietary information, whereas 61% felt they had received too little or far too little (Table 2).
Self reported dietary habits pre and post diagnosis shows a relatively equal split in those identifying with the prudent and Western dietary pattern. Only two participants changed their diets sufficiently to alter their classification from “Western” pattern to “prudent” pattern. For those participants who did report changing their dietary pattern at all post diagnosis, 18% attributed this change to the dietary advice they had received during their treatment.
For the participants who received dietary advice during treatment, 50% received advice relating specifically to their treatment (e.g. stoma advice, weight gain advice or advice for overcoming a low appetite), the other 50% received advice specific to CRC survivorship (e.g. reducing and avoiding red/processed meat and increasing fruits and vegetables).
Table 1. Participant demographic and disease characteristics
Table 2. Participant responses to needs assessment questionnaire
The relationship between BMI and dietary patterns is summarised in Table 3 and Figure 1. Data was analysed using Fischer’s exact test. No statistically significant results were observed on either initial categorisations or by combining categories into low/normal (BMI<18.5 and 18.5–25) or overweight/obese (BMI>25). Therefore data reported is considered indicative only.
A higher proportion of obese patients consumed a Western diet compared to healthy/low-weight individuals. No obese patient changed dietary pattern following diagnosis or treatment. Also, although a similar proportion of healthy-weight individuals received dietary advice, all obese patients stated they did not receive any advice. Despite this 33% of obese participants felt the dietary information received met their needs.
Differences in the perception of diet on recurrence was also analysed according to BMI, and measured according to a 5-point Likert scale with lower scores indicating lower degree of influence on risk of recurrence. Participants in the obese weight category were likely to consider that diet had less effect on cancer recurrence (2.16/5) than did participants in the healthy (2.93/5) and overweight (2.66/5) categories.
Table 3. Patients questionnaire responses according to WHO BMI category (kg/m2)
Figure 1. Percentage of participants following a Western dietary pattern according to BMI category
Overall, overweight and obese participants were more interested in receiving additional dietary advice with 84% and 67% respectively being ‘very interested’ in receiving this, compared to 60% of healthy weight participants. Obese participants were also more likely to consider changing their current diet based on such information with 84% reporting they would consider it in comparison to 78% of overweight and 74% of healthy weight participants.
Influence of dietary habits and advice according to presence of absence of stoma, and stoma location were recorded, however due to small numbers no reliable conclusions are able to be drawn (data not shown).
Presentation and delivery of additional dietary information—98% of participants would be ‘possibly’ or ‘very’ interested in receiving additional dietary advice. Only 5% of participants would not consider making dietary changes based on additional dietary advice, while 75% would consider making changes. Around 20% reported they were ‘unsure’ as to whether they would consider making dietary changes based on additional advice.
Only 10 % of participants reported they would like the information in the form of a CD or downloadable pdf. In comparison, 90% of participants wanted this information in the form of a pamphlet, 37% wanted this delivered by a doctor or nurse, and 53% wanted this delivered by a hospital dietitian.
This exploratory survey, conducted on a convenience sample of patients with colorectal cancer at differing stages of their colorectal cancer journey, aimed to ascertain the dietary patterns of patients, whether they recalled receiving dietary information and any changes they had made to their diet as a result of their condition or its treatment. A secondary goal was the development and testing of a patient booklet aimed at providing greater information to patients.
Our results indicate that our sample was generally representative of the NZ colorectal cancer population in terms of age and gender, however our sample contained no Māori or Pacific Island patients (representative of the incidence of CRC in the catchment of Southern DHB). We found only 38% of participants fell in the healthy weight range, while 45% were classified as overweight and 15% as obese. This matches the percentage of overweight participants in previous studies examining the relationship between BMI and CRC recurrence risk.18 Only one participant was classified as underweight.
Despite the strong evidence that obesity and dietary habits are important aetiologic factors in CRC, we found low levels of reported dietary-based intervention. Additionally, whilst 17/40 patients had a current stoma at the time of the survey, few had received dietary advice despite the potential influence of diet on stomal output.
We also found that no obese patients had received dietary information, even those who had resected and potentially cured colorectal cancer. This may indicate that health professionals are not offering appropriate intervention in the presence of obesity, perhaps seeing obesity as unrelated to cancer or as an unimportant patient outcome in the presence of a diagnosed cancer. Results also showed that although obese participants were less likely to feel the need for dietary advice during treatment, they are interested in receiving it after treatment and indicated that they would be responsive to such information. This finding indicates that obese patients may be more receptive to intervention than is currently perceived to be the case.
Our results also show that few patients are currently changing their dietary habits following a diagnosis of cancer, despite the potential for dietary patterns to reduce adenoma rates and despite the association with better cancer-outcomes. This may indicate that clinicians are as yet unaware of the association, or do not believe that the association between diet and cancer outcome is causal and therefore do not recommend change. However it is difficult to consider that obese patients should receive no dietary information, especially in the setting of particularly curative treatment, because of the multitude of concomitant health problems that may result from long-term obesity.
Our findings may reflect that colorectal cancer clinicians do not see it as their role to promote the role of dietary intervention in maintaining or improving health.
We note that the number of patients making dietary changes as a result of CRC is higher than the number receiving dietary advice, and that 60% of patients feel the level of dietary information they have received since diagnosis is too little to meet their needs. No participants felt the level of dietary information they had received was too much. Thus survivors of CRC feel there is currently a shortfall in the dietary information available. This is consistent with research which has found 80% of cancer patients (lung, colon or breast cancer) feel they need nutritional counselling, though only 17% currently receive this.19
Overall, 50% of participants indicated their current dietary pattern was high in Western dietary pattern index foods; a pattern associated with a higher rate of CRC recurrence.13 As research has shown that nutritional counselling in cancer survivors can improve dietary patterns,20 additional dietary advice could therefore positively influence CRC survivors’ dietary patterns by reducing intake of a Western dietary pattern.
Our findings are consistent with previous research which shows that approximately 30% of colorectal cancer survivors make dietary changes, and 45% begin taking new supplements without professional advice.19 In light of these findings it seems the availability of an accessible source of additional dietary information for CRC survivors is necessary and would be of benefit to patients.
All participants with an ileostomy reported they had made dietary changes because of their treatment, but only two thirds had received dietary advice. All participants with an ileostomy felt the level of dietary information received did not meet their needs. This is supported by research showing patients with an ileostomy feel confusion and frustration in relation to making dietary alterations and the amount of advice they receive.21
Our study has several limitations. Firstly, it was an opportunistic sample taken from patients available to the researchers during the time of an elective project. Therefore the sample was relatively small and included patients with completely resected as well as metastatic disease; these patients may have differing motivations and will clearly have different treatment goals.
The study also relied on patient recollections of dietary information given, rather than recording dietary habits as part of a prospective behavioural change programme. Therefore there is potential for recall bias. However if a patient who was given advice does not recall receiving this it may be that the information was given at a time which was not appropriate for that patient.
The challenge for practitioners is therefore to deliver advice in a manner that is sufficiently memorable and meaningful to be able to promote long-term healthy eating goals. Our study classified patients broadly into Western and prudent categories according to a non-validated tool, and caloric content was not considered. Use of a more comprehensive and validated tool would be valuable in a larger project.
Obesity, diabetes and metabolic syndrome22, 23 have also been associated with the development of CRC and poorer outcomes following a diagnosis. An unhealthy western dietary pattern, low in fruits and vegetables has also been attributed to the onset of these conditions. Whilst there is an association between dietary patterns and risk of colorectal cancer recurrence, it is not yet established that dietary manipulation can attenuate risk of recurrence. However the relationship is biologically plausible and consistent across cohort studies.
The USPPT also shows that compliance with a prudent-style diet can reduce the development of further polyps, so there remains an opportunity for effective intervention to prevent subsequent carcinogenesis even at a later stage in life. This lends biologic plausibility.
There are numerous studies assessing the effectiveness of dietary intervention in achieving behavioural change; the challenge remains to demonstrate that this results in improved cancer-related outcomes. In the absence of a formal structured dietary intervention, there is a burden on the clinician to interpret the available evidence, and offer useful and practical advice.
Our study demonstrates that CRC patients are relatively unaware of the extent to which diet can influence CRC recurrence risk although they are motivated to receive dietary information as currently many do not feel they have received enough dietary information. Patients with stomas feel their needs for dietary information are not met. In light of these findings, two dietary resources have been developed for the SDHB.
Competing interests: None declared.
Author information: Jessie M Pullar, Accredited Practising Dietitian. Perth, Australia; Alexandra Chisholm, Senior Lecturer, Department of Human Nutrition, University of Otago, Dunedin, New Zealand; Christopher Jackson, Senior Lecturer in Medicine, University of Otago, Dunedin, New Zealand
Acknowledgements: We are grateful to Professor Sheila Williams (Dept of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand) for her assistance with aspects of the statistical analysis.
Copies of the Dietary Resource developed in conjunction with this project can be found at http://www.southerncancernetwork.org.nz/file/fileid/36309
Correspondence: Dr Christopher Jackson, Senior Lecturer in Medicine, Department of Medicine, University of Otago, PO Box 913, Dunedin 9054 New Zealand. Email: Christopher.Jackson@southerndhb.govt.nz
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