Pancreatic cancer risk factors

Smoking is estimated to cause up to 20% of pancreatic cancers in the UK. 1. A British study reported that ex-smokers were 1.4 times more likely to die of pancreatic cancer compared with men who had never smoked. Current smokers of less than 25 cigarettes a day had 1.8 times the risk of death and smokers of 25 or more cigarettes a day were at 3.1 times the risk of never smokers 2.

Prospective studies have reported a positive trend with number of years of smoking among men but not women 3. Smokers are diagnosed on average 10 years younger than non-smokers 4. Studies have reported that risk returns to that of a never smoker from between 10-20 years after cessation 3,5. While the chemical cause is unclear, it is possible that N-nitroso compounds in tobacco are carried to the pancreas in the blood 6.

Regular cigar and/or pipe smokers have a 50% increased risk of pancreatic cancer 1. There is also evidence that risk increases with the use of snus although this may be limited to current smokers. 7,39

Chronic pancreatitis (CP), diagnosed in about one in 100,000 people in the UK each year, is a condition where the pancreas is inflamed. It is caused in the majority of cases by alcohol abuse. Risk estimates for pancreatic cancer in people suffering from CP range from 2 to 32 8-10.

People suffering from hereditary pancreatitis, which is characterised by onset before the age of 30 and a family history, have a risk ratio of at least 50 11,12, and an estimated lifetime risk of pancreatic cancer of 40-70% 13.

A meta-analysis reported a relative risk of 1.8 for pancreatic cancer in people with type II (non-insulin dependent) diabetes 14. A nested case-control study has recently reported results supporting this association, showing a statistically significant two-fold risk increase in people with biochemically diagnosed type II diabetes or with the highest fasting blood insulin levels 15.

Another meta-analysis showed that people with type I and early-onset diabetes have double the risk of pancreatic cancer 40

Obese individuals have a significant increase in risk of pancreatic cancer of 19% compared with individuals with a healthy body mass index (BMI) 16. Evidence points to a slightly stronger risk increase in men than women 3,17-21.

Evidence is inconsistent about the effect of physical activity on pancreatic cancer risk. A number of large cohort studies have reported no effect 21,22 while other cohort and case-control studies report a protective effect in people doing the greatest amount of moderate physical activity 17,23-26. Evidence suggests that physical activity has no effect in people with a healthy BMI and obesity has no effect in people with the highest levels of physical activity 23.

Studies show that people with at least one first-degree relative diagnosed with pancreatic cancer have almost double the risk of someone without a family history 41.

Overall, the contribution of dietary factors to pancreatic cancer risk is probably small. High dietary folate has been linked to a 51% reduced risk, but supplements have not been shown to have an effect. 45.

Chronic heavy alcohol consumption is a risk factor for pancreatitis, but evidence for an association with pancreatic cancer is inconsistent. Overall, research suggests an increased risk in heavy drinkers 27-29 , but no increased risk for people consuming up to 30g of alcohol a day 30.

Use of NSAIDs probably has no effect on risk of pancreatic cancer 46.

Significant reduction in risk has been reported in people with a history of allergies and risk decreases with increasing number of allergies and severity of symptoms 31. The relevant allergies are those affecting the skin, such as eczema or hives and reaction to insect bites, hay fever and respiratory allergies other than asthma 32.

There is some evidence that a history of peptic ulcer increases the risk of pancreatic cancer, although since smoking is related to peptic ulcer development, there is the chance for confounding by this factor 33. It has been suggested that the bacteria that populate the stomach post-operatively cause formation of carcinogenic nitrosamines 34. An increased risk of pancreatic cancer has been shown in male smokers testing positive for Helicobacter pylori, although another study showed no association, and any mechanism is uncertain 35,42. One study has shown a reduced risk of pancreatic cancer in people taking statins 43.

Findings relating to a number of other medical conditions, including gallbladder disease, or cholecystectomy, and hypertension, are inconsistent 36,37, 3,38.