A Harvard medical professor says patients of a Detroit-area cancer doctor were at high risk of infection because of excessive doses of powerful, expensive drugs.

Dr. Farid Fata will be sentenced in federal court for fraud. But a judge first is hearing from experts and patients this week. The hearing began Monday.

Testifying for the government, Dr. Dan Longo says some patients received a "stunning" number of injections of a drug called Rituximab. It's typically given eight times for aggressive lymphoma but one patient got it 94 times.

Fata pleaded guilty to committing millions of dollars in fraud against insurance companies and patients.

Prosecutors are seeking a 175-year prison sentence, while Fata is asking for no more than 25 years. Victims are in the courtroom.