Six additional veteran patients received incorrect doses of radiation during brachytherapy treatment for prostate cancer at the Philadelphia VA Medical Center, raising questions about whether still more cases are yet to be discovered in the ongoing investigation, according to a report in the Philadelphia Inquirer.

The newly reported cases, revealed to the U.S. Nuclear Regulatory Commission (NRC) last week, mean that 98 men—86 percent of the 114 brachytherapy patients at the facility—received too much or too little radiation from the start of the program in 2002 until it was shut down in June 2008.

The main target of the investigation is radiation oncologist Gary Kao, MD, who has since stopped seeing patients and is now performing lab work for the University of Pennsylvania School of Medicine in Philadelphia. Kao, among other things, is accused of doctoring reports after improperly implanting the radioactive seeds.

The Department of Veterans Affairs, which is expected to file a full report within the next two weeks, told the NRC that it was "reporting these six additional events to meet a regulatory requirement, not because of any anticipated harm to these patients."

Federal investigators who are examining the program identified systemic problems and failures of oversight as key reasons that the substandard treatments went undetected for so long despite numerous warning signs. They have discovered that a computer was disconnected from the medical center's network for 14 months in 2006 and 2007, and 23 patients were treated without critical post-implant dose calculations being performed.