Source: J Natl Cancer Inst, July 19, 2006;98(14):961-973.
Given the widespread use of nutritional modifications and supplements by those with cancer and concerns about the lack of benefit and possible harm, researchers conducted a systematic review of randomized controlled trials to examine the effect of nutritional interventions on patients with cancer or preinvasive lesions. They 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. It is important to note that the researchers excluded studies using synthetic retinoids, vitamin analogues, herbal supplements and polysaccharide K.
Researchers 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 impact of most nutritional interventions cannot be reliably estimated because of the limited number of trials, many of which were of low quality. Based on this, researchers concluded that there is currently no evidence that dietary modification by cancer patients improves survival and benefits disease prognosis.