Mary Berg is paying the price for a shortage of U.S. doctors that by most accounts is about to get much worse.

After finding out in 2006 she had a rare and deadly gastrointestinal cancer, the 49-year-old mother of a teen-aged daughter found there were no doctors in Nevada who specialized in her type of tumor. Only one cancer center took her insurance. And because the tumor had spread, the need for a liver transplant was a distinct possibility, though no surgeons in the state were qualified to do the procedure.