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Pancreatic cancer, long thought by doctors to be fast growing and almost unbeatable, develops slowly enough to allow for at least a decade of screening that may increase chances of survival, university researchers said.
Tissue from seven newly deceased patients showed that cells in the pancreas took at least 10 years to mutate enough to produce the first cancer cells, and seven more years before a tumor could develop and become capable of spreading to other organs. On average, patients died two years after all that, according to a study released Wednesday in Nature.
The pace of pancreatic cancer means that earlier detection could bring survival rates more in line with patients who have prostate, breast or colon tumors. Most malignancies of the pancreas, a gland behind the stomach, are diagnosed in the final two years, as there's usually no screening for the illness until symptoms appear, said Christine Iacobuzio-Donahue, a cancer researcher who is an author of the study.
"The medical community has approached pancreatic cancer with the mindset that there is nothing much we can do about it," said Iacobuzio-Donahue, an associate professor of pathology and oncology at Johns Hopkins University School of Medicine, in Baltimore. "That was because we had always assumed that its development was a very rapid process. In fact, the progression of the disease is not that different from other cancers."
With earlier detection, doctors could remove precancerous cells before they develop into a tumor, much as they excise polyps to prevent colon cancer, Iacobuzio-Donahue said. This year in the U.S., there will be 36,800 deaths from the pancreatic cancer and 43,140 new cases, according to estimates by the National Cancer Institute, based in Bethesda, Maryland.
Today, just 6 percent of patients survive at least five years after being diagnosed with pancreatic cancer, while the rates are 65 percent for colon and rectal cancer, 89 percent for breast cancer, and 100 percent for prostate cancer, according to the American Cancer Society, based in Atlanta.
Two-thirds of patients diagnosed with pancreatic cancer have shown evidence that their malignancy has metastasized, or spread to other organs, Iacobuzio-Donahue said. The study found that metastasis, which often is the cause of death, occurs late in the development of pancreatic cancer, leaving time for detection of the disease earlier.
Screening for pancreatic cancer would be more complex than a mammogram, a prostate-related blood test or a colonoscopy. Iacobuzio-Donahue said it would require getting an endoscopy — which gives doctors a look inside the body through a tiny camera at the end of a long, thin tube — coupled with ultrasound, an imaging technique using sound waves.
Conventional tests and treatments have limitations, as the procedures are based on a shorter timetable for the disease's progression, said Bert Vogelstein, a study author and the director of the Ludwig Center for Cancer Genetics & Therapeutics, at Johns Hopkins.
The disease's long gestation period "leaves room to develop new early, diagnostic tools and intervene with potentially curative surgery," Vogelstein said in a statement.
Vogelstein led the Pancreatic Cancer Genome Project, which sequenced more than 20,000 genes to decode the series of cell mutations that results in the disease. Findings from the initiative, completed in 2008, became the basis for the Nature study.
Patients currently get tested after they experience pain or show jaundice, Iacobuzio-Donahue said. Because there are few nerves in the pancreas, the pain is caused when the tumor grows beyond the gland into areas with nerves. The tumor causes jaundice by enlarging to the point that it compresses a bile duct, she said.
Iacobuzio-Donahue employed a rapid-autopsy program, used in the study of Alzheimer's disease and Parkinson's, to garner the consent of dying patients to allow an immediate autopsy to retrieve live tumor cells.
The genome sequencing was funded partly by the U.S. National Institutes of Health, based in Bethesda; the Bill & Melinda Gates Foundation, based in Seattle; and the Sol Goldman Pancreatic Cancer Research Center, at Johns Hopkins.