While the gossip rag says it has confirmed the report, others may be more skeptical. Apple said last week that Jobs, who took medical leave from the company in January, is doing well and conducting meetings out of his home.
However, the National Enquirer -- take it for what it's worth -- is backing RadarOnline's story and taking it a step further.
The notorious paper reportedly has pictures of Jobs, 55, at the clinic. One photo claims to show a skeletal Jobs getting out of his car to receive treatment "a day after he turned in a full day's work when he was spotted on Apple's Cupertino campus."
He was seen at Apple's campus last week.
Jobs took time off from Apple in 2004 to treat a very rare form of pancreatic cancer. He turns 56 next week.