Glycemic load raises colon cancer recurrence risk

Increased glycemic loads and high carbohydrate consumption may increase the risk for colon cancer recurrence, show the results of a US study.

Furthermore, the impact of these dietary factors on survival primarily affected overweight and obese patients.

"These findings support the potential role of energy balance factors in colon cancer progression and may offer opportunities to further improve patient survival," say Jeffrey Meyerhardt (Dana-Farber Cancer Institute, Boston, Massachusetts, USA) and colleagues.

The study was part of a trial of adjuvant chemotherapy to surgery for stage III colon cancer. It included 1011 patients who recorded their dietary intake using a food frequency questionnaire during chemotherapy and for 6 months afterwards.

Meyerhardt and colleagues calculated patients' average daily glycemic load such that each unit represents the equivalent of 1 g of carbohydrate from white bread. They found that patients in the lowest quintile for dietary glycemic load had a 79% increased chance of disease-free survival compared with those in the highest quintile (48 vs 36%).

Similarly, patients in the highest quintile of carbohydrate consumption had an 80% increased risk for cancer recurrence or death from any cause compared with patients in the lowest quintile (49 vs 34%).

Interestingly, further analysis revealed that the relationship between glycemic load and disease-free survival was modified by body mass index (BMI). Those with a BMI of 25 kg/m² or more had a 2.3-fold increase in the risk if they were in the highest quintile for glycemic load compared with those in the lowest quintile.

By contrast, there was no statistical relationship between glycemic index and survival in patients with a BMI of less than 25 kg/m².

The authors explain that there is growing evidence that insulin production may be related to tumor growth and recurrence.

"We hypothesize that excess energy balance, including higher dietary glycemic load, may stimulate systemic insulin production, which may, in turn, promote cell proliferation and inhibit apoptosis of micrometastases," they write in the Journal of the National Cancer Institute.

The authors are conducting further research to confirm their results in other cohorts of colon cancer patients.

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