Cancer experts said Wednesday that there was little remarkable about the progress of the rare, relatively slow-moving form of pancreatic cancer that afflicted Apple Inc.'s co-founder Steve Jobs for at least the past seven years, except that he had a liver transplant as part of his treatment.

'Living six or eight years following a diagnosis is not unusual,' said Margaret Tempero, a pancreatic-cancerexpert at the University of California, San Francisco, who wasn't involved in treating Mr. Jobs.

Apple didn't comment on the cause of Mr. Jobs's death; the exact cause remains unclear. His battle with his illness led to his decision in late August to relinquish the chief executive post at Apple.

Over the years, Mr. Jobs and Apple released so little information about his medical condition that they encountered criticism from corporate-governance advocates for the lack of disclosure. Few people outside of his doctors and inner circle know the details of his treatment. None of the doctors quoted in this story treated Mr. Jobs or has any direct knowledge of his condition or care.

About 40,000 Americans are diagnosed with pancreatic cancer each year and for the vast majority it is quick death sentence: about 80% die within the first year after diagnosis, according to the National Cancer Institute.

But Mr. Jobs had what is called a neuroendocrine pancreatic tumor, a type that accounts for fewer than 5% of pancreatic cancers and, experts say, differs substantially from the more common kind.

'The two different types have fairly dramatically different clinical behaviors,' said Matthew Kulke, director of the carcinoid and pancreatic neuroendocrine tumor program at the Harvard-affiliated Dana-Farber Cancer Institute in Boston. Typically, the neuroendocrine tumor 'will grow more slowly and patients can do quite well, sometimes for several years.'

Mr. Jobs had the tumor surgically removed in 2004, a procedure he said at the time was successful.

Michaela Banck, a pancreatic cancerexpert at Mayo Clinic, said there are two reasons to undergosurgery for such a tumor. 'If you think it is confined to the pancreas, there is quite a good hope that the patient has gotten rid of it once and for all,' she said.

But if the cancer has spread to the liver, 'you can't ultimately cure it. The more tumor you remove, you buy time for the patient,' she added. 'You kind of reset the clock.'

After the 2004 surgery, Mr. Jobs and his company said little about his health until January 2009, when his significant weight loss and a decision to forgo his customary appearance at a major trade show raised new concerns.

Initially that month, Mr. Jobs attributed his weight loss to a 'hormonal imbalance' that was being treated nutritionally. But a week later, he said his condition was 'more complex,' and he took a leave of absence.

Mr. Jobs underwent his liver transplant in 2009. While there are some published studies describing liver transplant as a treatment option for neuroendocrine pancreatic tumors, it isn't a common approach, experts said.

One worry is that drugs used to prevent rejection of a transplantdepress the immune system, and 'cancers can grow rapidly afterward,' said the USCF's Dr. Tempero. But, 'it's all speculation.'