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| Journal of the New Zealand Medical Association,
08-June-2012, Vol 125 No 1356
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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.
MethodsStudy 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.
ResultsA 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.
DiscussionThis 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
References:
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