Nutritional interventions and outcome in patients with cancer or preinvasive lesions: systematic review.
BACKGROUND
Dietary modifications and supplements are used widely by patients with cancer and preinvasive lesions as an adjunct to standard treatment. Given the widespread use of nutritional modifications and supplements by such patients and concerns about the lack of benefit and possible harm, we conducted a systematic review of randomized controlled trials to examine the effect of nutritional interventions on patients with cancer or preinvasive lesions.


METHODS
We searched electronic databases and reference lists to locate all eligible trials and analyzed trial quality. Outcome measures were all-cause and cancer mortality, disease-free survival, cancer recurrence, second primary cancer, recurrence of a preinvasive lesion, or progression to cancer. Results of individual trials were combined by use of random-effects meta-analyses.


RESULTS
We identified 59 eligible trials, 25 in patients with cancer and 34 in patients with preinvasive lesions, respectively. Trial quality was generally low; only three trials (two of cancer and one of preinvasive lesions) had adequate methods for generating the allocation sequence, allocation concealment, and masking both outcome assessors and participants. The combined odds ratio (OR) for the effect of a healthy diet-given alone or with dietary supplements, weight loss, or exercise-on all-cause mortality was 0.90 (95% confidence interval [CI] = 0.46 to 1.77). There was no evidence of an association between the use of antioxidant (OR = 1.01, 95% CI = 0.88 to 1.15) or retinol (OR = 0.97, 95% CI = 0.83 to 1.13) supplements and all-cause mortality. Meta-analyses of all other outcomes did not show clear evidence of benefit or harm.


CONCLUSIONS
The impact of most nutritional interventions cannot be reliably estimated because of the limited number of trials, many of which were of low quality. There is no evidence that dietary modification by cancer patients improves survival and benefits disease prognosis.
Davies
Anna A
AA
Department of Social Medicine, University of Bristol, Lower Maudlin St., Bristol BS1 2LY, UK.
Davey Smith
George
G
Harbord
Roger
R
Bekkering
Geertruida E
GE
Sterne
Jonathan A C
JA
Beynon
Rebecca
R
Thomas
Steven
S
D000975:Antioxidants / Q000008:administration & dosage; D000529:Complementary Therapies; D018849:Controlled Clinical Trials as Topic; D019587:Dietary Supplements; D018450:Disease Progression; D018572:Disease-Free Survival; D004311:Double-Blind Method; D005247:Feeding Behavior; D006801:Humans; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology; D009369:Neoplasms / Q000178:diet therapy / Q000401:mortality / Q000628:therapy*; D016609:Neoplasms, Second Primary / Q000453:epidemiology; D016017:Odds Ratio; D011230:Precancerous Conditions / Q000178:diet therapy / Q000401:mortality / Q000628:therapy*; D011379:Prognosis; D012107:Research Design; D016037:Single-Blind Method; D014815:Vitamins / Q000008:administration & dosage*; D015431:Weight Loss
D000975:Antioxidants; D014815:Vitamins