Cigarette smoking, already known to double the risk of pancreatic cancer, may also cause the deadly cancer to strike decades earlier in smokers than in non-smokers.
A study of almost 500 people with hereditary pancreatitis found that smokers developed pancreatic cancer about 20 years earlier than non-smokers did.
The findings, which appear as a letter in the Wednesday edition of the Journal of the American Medical Association, provide insight into how smoking affects cancers in organs that are not directly exposed to smoke, said Dr. David Whitcomb, a gastroenterologist at the University of Pittsburgh and a study co-author. Smoking also increases the risk of cervical, bladder and kidney cancers.
Hereditary pancreatitis is a rare genetic disease that causes chronic inflammation of the pancreas, a gland that produces digestive enzymes and such hormones as insulin. Only about 1,000 Americans have this disease, but researchers are interested in studying these patients because they are at high risk for pancreatic cancer.
People in the general population have a little less than a 1 percent risk of developing pancreatic cancer by age 70; people with hereditary pancreatitis face a 40 percent risk, Whitcomb said.
The study was based on a registry of 497 patients with hereditary pancreatitis. Of those patients, 19 had pancreatic cancers. Eleven of the cancer patients were current or former smokers, six were non-smokers and the smoking histories of the remaining two were unknown.
Smoking doubled the risk of pancreatic cancer in these patients, just as it does in the general population, they found. What was surprising, however, was that the cancer developed at a mean age of 50 among the smokers, compared with 70 in the non-smokers.
Whitcomb said this effect of smoking on the age of cancer onset also may occur among people who don't have hereditary pancreatitis, but is not as obvious because the incidence rate of the cancer is much lower in the general population.
The authors of the report, which include pancreatic cancer specialist Albert Lowenfels of New York Medical College, noted that further study will be necessary to determine if smoking has a similar effect on other patients with an inherited susceptibility to pancreatic cancer.
Pancreatic cancer is the fourth-leading cause of cancer deaths. It is particularly deadly because it generally develops without symptoms - and goes undetected - until the cancer is in its advanced stages. About 29,000 Americans are diagnosed with pancreatic cancer each year; only about 4 percent are still alive five years later.