Recent media reports have begun to shed more light on Steve Jobs' medical condition and the treatment he's believed to have sought overseas.
According to Fortune magazine, the co-founder and chief executive of Apple, Inc, who is currently on medical leave, flew to Switzerland in 2009 to receive a treatment for neuroendocrine cancer that isn't yet approved in the U.S. The Wall Street Journal reported Jobs also had a liver transplant that year.
Fortune said it learned about the unpublicized trip to Switzerland from former Apple director Jerry York, who died in 2010.
In 2004, doctors found that Jobs had a pancreatic neuroendocrine islet cell tumor, which is very different from the more well-known pancreatic cancer that took the life of actor Patrick Swayze in 2009.
"They are slower-growing tumors than typical pancreatic cancers. The survival rate for more typical cancers is much lower," said Dr. Alejandro Ayala, associate clinical professor of medicine at the University of Miami's Miller School of Medicine.
"Some people have described them as cancer in slow motion," said Dr. Jonathan Strosberg, attending physician at the Moffitt Cancer Center in Tampa, Fla. "Patients tend to live longer, even if it's in its later stages. The average survival is six years from diagnosis."
Neuroendocrine cancers affect cells throughout the body that secrete hormones. The tumors can cause the secretion of either too much hormone or not enough. They are relatively rare, but more and more new cases are being diagnosed, and experts attribute that trend to better recognition of these tumors.
Jobs' Swiss Treatment Experimental and Effective
Experts say the treatment Jobs underwent is an experimental procedure called peptide receptor radionuclide therapy (PRRT). It involves delivering radiation to tumor cells by attaching one of two radioactive isotopes to a drug that mimics somatostatin, the hormone that regulates the entire endocrine system and the secretion of other hormones.
Specialists who treat neuroendocrine cancers say PRRT is very effective, but because the U.S. Food and Drug Administration hasn't yet approved it, patients who want the treatment typically head to Europe for it.
"It shrinks tumors in about a third of cases significantly, and it lasts on average about two to three years," said Strosberg.
"Even though you get tumor shrinkage, you mostly get disease progression that stabilizes," said Dr. Thomas O'Dorisio, professor of medicine at the University of Iowa in Iowa City.
Experts believe the FDA will eventually approve PRRT.
"The data are coming out slowly. There's never been a phase 3 clinical trial, and that's why it's not okayed yet," said O'Dorisio.
"It's a new, experimental treatment, and it has to go through the same approval process as all drugs," said Ayala.
PRRT Treatment Also Costly
A company called Excel Diagnostics Imaging Clinics, based out of Houston, Tex., was approved by the FDA to begin an investigational new drug trial for PRRT. However, O'Dorisio said it's cheaper to get the therapy at University Hospital of Basel in Switzerland, where Jobs is believed to have received his.
"It's $4,200 per treatment at Basel," said O'Dorisio. He said patients generally receive four treatments. He estimates the cost of treatment in Texas at $15,000 per treatment, which may or may not be covered by health insurance.
He also said he's sent about 400 of his patients to Basel because of the cost, and because the hospital there offers the best treatment.
Other treatment options include surgical removal of the primary tumor, and a drug called sandostatin that mimics the action of somatostatin and other drugs that are FDA-approved for kidney cancer that have also shown promise against pancreatic neuroendocrine tumors. Experts say there are also other radiotherapeutic agents currently in development.
Pancreatic neuroendocrine cancer often spreads to the liver, which experts believe happened to Jobs, but liver transplants are generally not an option for people with neuroendocrine cancers.
"People with liver tumors can live for very long. They are very slow-growing and they are not candidates for liver transplants," said O'Dorisio.
It's difficult to predict how long Jobs will survive, since survival depends on a number of factors, and Jobs has kept details about his condition private.
"Survival depends on the aggressiveness of the tumor and if it's malignant," said Ayala.
ABC News' Lara Salahi, Kristina Fiore, Becky Bielang and Scott Dunbar contributed to this report.