Globally, pancreatic cancer represents the fourth leading cause of cancer death, imposing serious threats on public health. Pancreatic cancer has a poor prognosis and high fatality rates, with a 5-year survival rate of less than 5%. Efficient screening methods or treatment modalities for this malignancy are still lacking, highlighting the importance of effective prevention strategies. Known risk factors for pancreatic cancer include chronic pancreatitis, cigarette smoking, family history, excess body fat and diabetes. Dietary factors may also pay a role in the development of pancreatic cancer, but few certainties have been achieved.
Multiple lines of evidence has shown that marine-derived n-3 polyunsaturated fatty acids (PUFA); such as eicosapentaenoic acid and docosahexaenoic acid have inhibition effects on a number of aspects of inflammation. Therefore, it is biologically plausible that consumption of fish, a major dietary source of marine n-3 PUFA; may provide protections against cancer. Therefore, they carried out an update meta-analysis to comprehensively evaluate; the relationship between long-term fish consumption and risk of pancreatic cancer.
Risk of pancreatic cancer
The meta-analysis included 13 studies that prospectively investigated; the relationship between fish consumption and risk of pancreatic cancers. These 13 studies were published between 1993 and 2018; including 4994 pancreatic cancer cases and 1,794,601 participants. The median number of cases and participants was 300 (54 to 1156) and 82,024 (3980 to 510,314), respectively. The median length of follow-up was 11.3 (6.8 to 17.4) years.
Five studies were from the US, four studies were from Asia (two from Japan and one each from China and Iran); and four studies were from Europe (one each from Finland, Sweden and the Netherland in addition to one study conducted in 10 European countries). Participants were male (n = 2) or female (n = 2) only in four studies and the remainder included both sexes. While all studies included in the meta-analysis made multivariate adjustments, the potential confounders considered in the analyses varied.
In the updated meta-analysis of 13 prospective studies including approximately 1.8 million participants and 5000 pancreatic cancer cases; long-term fish consumption was not significantly associate with risk of pancreatic cancer. The findings were concordance with results from a previous meta-analysis; that included eight prospective studies with only 1853 cancer cases and 0.54 million participants. The meta-analysis updated the evidence by adding five prospective studies with 3141 cases; and 1.26 million participants and, therefore, had sufficient statistical power to detect any moderate association between fish consumption and risk of pancreatic cancers.
Inverse associations between fish consumption
Results of this large updated meta-analysis suggest that fish consumption; is not significantly associated with risk of pancreatic cancer. Accumulative evidence has suggested that red and processed meat may increase risk of various digestive malignancies; in particular with colorectal, esophageal and gastric cancers.
A recent meta-analysis of cohort studies also suggested that consumption of red and processed meat; associated with increased risk of pancreatic cancer in men. Despite that our and other studies showed no or only weak-to-moderate inverse associations between fish consumption and risk of the aforementioned cancers; dietary fish is still a good source of animal protein and can be recommended as a substitution for red and processed meat in regular diets for cancer prevention.