Dietary Inflammatory Index, Alternative Healthy Eating Index-2010, Mediterranean Diet Score and the risk of pancreatic cancer

1Introduction

Pancreatic cancer is the seventh leading cause of cancer death worldwide, causing 466,003 deaths (4.7% of all cancer deaths) in 2020 [1] . Incidence is highest in Europe, Northern America, and Australia/New Zealand, and lowest in Asia and Africa [12] . In Australia, pancreatic cancer is the eighth most commonly diagnosed cancer and fifth most common cause of cancer death, with more than 3391 Australians projected to die from the disease in 2021 [3] . Despite improvement in treatments, five-year survival is 12% [3] . Previously identified factors that increase risk of pancreatic cancer include older age, male sex, ethnicity (African Americans have increased risk relative to European Americans), cigarette smoking, alcohol drinking, dietary factors (red and processed meat, food and beverages containing fructose and foods containing saturated fat), taller adult height, higher body fatness, diabetes, chronic pancreatitis, family history and specific genetic variants [24] .

There is growing evidence that inflammation contributes to the development of specific types of malignancies; this is supported by the observed associations of inflammatory bowel disease with colorectal cancer, viral hepatitis with hepatocellular carcinoma, and pelvic inflammatory disease with ovarian cancer [5] . Similarly, the association between chronic pancreatitis and pancreatic cancer suggests a role for inflammation in the aetiology of pancreatic cancer [6] .

Dietary components and patterns have been observed to be associated with various inflammatory mediators, [7] and intervention studies using a Mediterranean Diet have been shown to reduce circulating concentrations of inflammatory biomarkers [8] . Healthy diets defined in other ways may also work through inflammation and we have shown associations of Mediterranean Diet Score (MDS), Alternative Healthy Eating Index-2010 (AHEI-2010), and Dietary Inflammatory Index (DII) with circulating concentrations of inflammatory biomarkers [9] . Numerous studies have identified dietary patterns as potential risk factors for common cancers like breast and colorectal, [10] but the few reports for pancreatic cancer have been inconsistent [1112] . Two systematic reviews from 2017 assessed dietary patterns and risk of pancreatic cancer; although there was some evidence that healthier diets were associated with reduced risk, both concluded that more evidence from prospective studies was required [1112] .

In view of what is already known about diet, inflammation and cancer, our aim was to investigate the effect of MDS, AHEI-2010 and DII on risk of pancreatic cancer in the Melbourne Collaborative Cohort Study (MCCS). We have previously reported evidence from the MCCS of associations between these three dietary scores (particularly AHEI-2010) and measures of obesity, as well as risk of diabetes, both of which are risk factors for pancreatic cancer [1314] .