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8th August 2022
Resistant starch does not reduce colorectal cancer (CRC) among patients with Lynch syndrome (LS) but does significantly lower the risk of developing non-colorectal LS cancers, according to the findings of a randomised, placebo-controlled trial by an international research team.
Lynch syndrome is characterised by an increased risk for the development of colorectal cancer, endometrial cancer and various other cancers because of a mutation in one of several mismatch repair genes. In effect, LS can be described as a hereditary cancer syndrome and is estimated that 1 in every 300 people may be carriers of an alteration in a gene associated with it. In the UK, NICE has recommended that in order to reduce the risk of colorectal cancer in patients with LS, that daily aspirin, to be taken for more than 2 years. Another option to help reduce the risk of CRC is through greater intake of dietary fibre. In 1972, Burkitt suggested that dietary fibre has a role in the prevention of certain large-bowel and other diseases which have become prevalent in Western countries. Despite this belief which has subsequently popularised the importance of fibre for the prevention of colorectal cancer, a 2005 meta-analysis concluded that while dietary fibre intake is inversely associated with risk of colorectal cancer in age-adjusted analyses, after adjusting for other dietary risk factors, the association became non-significant.
In recent years, resistant starch, which is present in foods such as green bananas, has become an area of interest due to its potential to exert a healthy impact on the gut and certain members of its resident microbiota, particularly through enhanced butyrate production. In the present study, researchers recruited patients with LS as part of the CAPP2 study in which participants were randomised to receive aspirin and/or resistant starch and followed for several years with the primary hypothesis being that both interventions might prevent colorectal cancer. In the current paper, the researchers focused on CAPP2 participants randomly assigned to resistant starch, which was given as a 30g daily supplement or matching placebo. The primary outcome was the development of colorectal cancers after 2 years whereas secondary outcomes focused on non-colorectal LS cancers which included those affecting the stomach/duodenum, urinary, ovarian and bile duct pancreas. In addition, non-LS cancer incidence, such as bladder, bone, breast, lung and many others, were also examined.
Resistant starch and cancer outcomes
A total of 918 participants with a mean age of 45 years (56.3% female) were included in the analysis, 463 of whom were randomised to resistant starch and followed for a mean of 25 months.
A total of 52 and 53 participants developed colorectal cancer in the resistant starch and placebo groups, which was not significantly different (incidence rate ratio, IRR = 0.85, 95% CI 0.58 – 1.25, p = 0.41). However, more patients in the placebo group developed non-colorectal LS cancers (27 vs 53) and this difference was significant (IRR = 0.52, 95% CI 0.32 – 0.84, p = 0.0075). Despite this reduction, there was no difference between the two groups for non-LS cancers (IRR = 0.88, 95% CI 0.56 – 1.40, p = 0.60).
The authors discussed that while resistant starch did not reduce colorectal cancer, there was a significant effect against non-colorectal LS cancers and concluded that this should be investigated further.
Mathers JC et al. Cancer Prevention with Resistant Starch in Lynch Syndrome Patients in the CAPP2-Randomized Placebo Controlled Trial: Planned 10-Year Follow-up Cancer Prev Res (Phila) 2022