So, as CBS News Correspondent Jim Acosta reports, when doctors ordered him to take a break from chemotherapy, "It didn't feel right," says his wife Judie.
They'd heard about the Parker Hughes Cancer Center outside Minneapolis.
Its infomercials feature the center's director, acclaimed cancer researcher doctor Fatih Uckun.
"They offered hope," says Judie.
At Parker Hughes, Dan was placed on a radical regimen of chemotherapy and as many as 15 new drugs.
"I had boxes of them in my refrigerator," says Judie
Alongside the milk and butter, sat $10,000 worth of medicine.
While Dan's medical bill ran well over $100,000, Judie says she was given the impression her husband's life would be extended by years. He died after eight months of treatment.
"He wasn't in stage four cancer when he went there," says Judie. "Why would he die from it that quickly?"
"He died primarily, it appears, of complications of treatment," says respected oncologist Dr. Harold Londer.
Londer reviewed Cervenka's records for CBS News. He says doctors at Parker Hughes mixed Dan's drugs like "kids with a chemistry set."
"The combination of drugs leaps around in a way that seems almost inherently random when you really analyze it," says Londer.
"I stand by those treatment decisions," says Uckun.
Uckun, who is not board certified in oncology, says Cervenka came to him a sick man.
"He knew that his disease was not curable," says Uckun. "We did exactly what he asked us to do.
"You are dealing with a patient who has multiple health problems involving his heart."
Uckun repeats this claim of heart problems throughout his interview with CBS News, but according to medical records he signed himself, there was no heart condition.
When told that an outside medical expert had said Uckun's treatment of Mr. Cervenka was excessive, Uckun responded by saying "This treatment had been used by several opinion leaders and found to be effective."
Stacia Christians quit her job as a nurse at Parker Hughes, convinced the center's patients were overtreated and overbilled.
"I thought it was insurance fraud, I thought it was Medicare fraud," she says. "I worried about patients, I worried about my own license."
Uckun acknowledges he's under investigation by state authorities, but he claims the critics who sparked those investigations are competitors who want to shut him down.
Sean Heide insists Uckun's aggressive approach saved his life after other doctors gave up.
"In the eyes of the guy with cancer and the doctor trying to save your life, excess isn't in the vocabulary," says Heide.
But, Judie thinks it's about money.
With so many questions, she's going to court to get answers to whether her husband's cancer clinic was selling hope all the way to the bank.