I sure hope that the amount of truth in this story is on par with other stories that are run in The National Enquirer. Translation: no truth to it at all.
The Enquirer is hit-and-miss. To suggest they're 100% fiction would be disregarding much of their track record...
They were first to publish certain candid (and accurate) details about the Lewinsky affair.
They were first to dig up photos of OJ Simpson in Bruno Magli shoes after OJ had vehemently denied ever owning such shoes.
They uncovered that Jesse Jackson had an illegitimate child.
They were first to break the story that OJ was to publish a book called "I Did It"; the story was flatly denied but then the book showed up a month later.
They broke the story that Rush Limbaugh was addicted to painkillers, later confirmed to be true.
They broke stories about Mel Gibson and Billy Joel both having marital problems, and both men indeed announced their divorces months later.
They were first to allege that Tiger Woods was having extramarital affairs, after which several women came forward supporting this claim.
In January 2009 they accurately predicted that Michael Jackson had 6 months to live, although that's more of a lucky shot than accurate reporting - his death was accidental.
The story in question hinges on the credibility of these two doctors, and I don't know what to make of that. On one hand alarm bells go off when they make a precise verdict based on some paparazzi shots. On the other hand they might have looked at many more (and perhaps more revealing) pictures than those which NE chose to publish. He does look even thinner than the 'new' thin Jobs we're used to, it does appear confirmed that he checked in at Stanford Cancer Center, and both Steve and Apple have been very quiet about this new leave of absence, more so than the previous time (2009). The last time, Jobs gave a finite timeline (he'd be back in June), this time it's open-ended.