Imprisoned: Dr Farid Fata (pictured) - who netted millions of dollars by putting 550 patients through unnecessary cancer treatments and then billing their insurers - has been sentenced to 45 years in prison
Office manager told Feds his boss was falsely diagnosing cancer and forcing patients into bankruptcy
Office manager George Karadsheh ran Dr Farid Fata's cancer center
He asked doctors why they were resigning, discovered the conspiracy
Took the case to the US Justice Department and Fata was arrested
Dr Fata gave 533 patients excessive and grueling cancer treatments
He then billed insurance firms, scamming millions of dollars in the process
Victims, some of whom did not actually have cancer, had health wrecked
Sustained brittle bones and fried organs, with one losing both of his legs
Some patients lost their homes and jobs, and were forced into bankruptcy
On Friday, Fata broke down in court as he was imprisoned for 45 years
An office manager has described how he came to expose his doctor employer who netted millions of dollars by putting more than 500 patients through unnecessary and grueling cancer treatments and then billing insurers.
George Karadsheh said he was suspicious at the frequent rate of resignations at Dr Farid Fata's Crittenton Cancer Center in suburban Detroit.
He probed a number of outgoing medics, who told him they suspected chemotherapy was being given to patients who had not been diagnosed with cancer.
After investigating the case himself, Karadsheh felt he had enough evidence to the US Justice Department in 2013. In August that year, Fata was arrested.
Fata was jailed on Friday for 45 years for poisoning around 550 victims - many of whom did not actually have cancer - by giving them excessive chemotherapy and other treatments.
His actions wrecked his patients' health, with many sustaining chronic health problems such as brittle bones and fried organs. Other victims lost their homes and jobs, and were forced into bankruptcy.
In a final hearing, prosecutor Barbara McQuade branded Fata 'the most egregious fraudster in the history of this country'.
'It was so difficult to believe,' Karadsheh told ABC's Nightline.
'Here is a physician whose background is second to none in Michigan. I had never had a patient complain that there was a problem with a reaction to a drug or whether it was necessary.'
The case came to light, he said, when he spoke to an accomplished doctor to ask why he handed in his resignation. The doctor 'explained that Dr Fata was actually administering chemotherapy to patients without need,' Karadsheh said.
'He was also explaining that patients who were on hospice were taken off hospice and put on chemotherapy, put back on chemotherapy.
'He also pointed out that patients who were receiving chemotherapy without disease were receiving it to the very last day of life.
'So at that point I discovered that there may be some issues there.'
On Friday, Fata broke down in court as he was sentenced to more than four decades in prison for what the judge described as a 'huge, horrific series of criminal acts' that had affected hundreds.