Major nonprofit medical systems in North Carolina are dramatically marking up prices for chemotherapy drugs as they take on a bigger share of the state’s market for cancer treatment, according to a joint investigation by the Charlotte Observer and The News & Observer of Raleigh.

A review of thousands of claims involving seven cancer drugs by the newspapers found that hospitals and hospital-owned clinics charged far more—sometimes several times more—for the medications than independent oncology practices. Such practices are increasingly being bought up by big medical systems, leading to significant price hikes for patients.

Hospital officials said they must charge more for some services to make up for losses incurred in others—for example, treating the uninsured and Medicaid patients—a problem not faced by independent practitioners, who can and often do refer such patients to hospitals.