LOS ANGELES — Steve Jobs' decision to take a medical leave from Apple Inc. was probably triggered either by an infection, a rejection episode related to his recent liver transplant or, most likely, a recurrence of his pancreatic cancer, experts said Monday.
But all cautioned that these are just educated guesses because so few details about his medical condition have been made public. "If we don't know more, it is all speculation," said Dr. Heinz-Josef Lenz, a gastrointestinal oncologist at the University of Southern California's Norris Comprehensive Cancer Center. "But we worry the tumor is back."
Jobs' cancer, diagnosed in 2003 is known as an islet cell neuroendocrine tumor. That is a much rarer form of pancreatic tumor than the type suffered by actor Patrick Swayze, who died in 2009, but also a much more survivable form.
If caught early, it is usually treated successfully by surgical removal of the tumor. However, the cancer frequently spreads to the liver, and Jobs' apparently did so without being initially detected. When doctors finally identified it there, "there must have been too many tumors within the liver" to permit surgical removal, said Dr. Gagandeep Singh, chief of hepatobiliary surgery at City of Hope in Duarte, Calif.
Physicians thus had no choice but to remove the entire liver and perform a transplant, a procedure that was done in 2009. But the transplant would not have been done if doctors were not confident all of the cancer had been removed, experts said. If even small pockets of tumor remained behind, Singh said, the fear is that "the cancer will come back with a vengeance" because the immune system has to be suppressed in transplant recipients, leaving it less able to fight the cancer.
Dr. Anthony Heaney, an endocrinologist at the University of California, Los Angeles' Reagan Medical Center, said that "the challenge is, even with the very sophisticated and detailed evaluations we can undertake, if there is a micrometastasis (tiny pockets of cancer cells) sitting in a lymph node somewhere, we may not pick it up." When immunosuppressive drugs are started, the tumor cells can then "begin to develop and blossom."
Very little is known about long-term survival following such transplants, Singh said. The medical literature records no more than 20 such cases. For those few cases, the one-year survival is about 80 percent to 85 percent and the five-year survival is about 40 percent, he said.
Another possibility is that the immunosuppressive drugs could also be allowing an infection to become more aggressive because Jobs' body is not able to fight it off.
The fact that Jobs is taking a leave "would indicate that he is planning to undertake a program of treatment," Heaney said.