Aug. 18--A review has found that six additional veterans received incorrect doses of radiation during prostate cancer treatment at the Philadelphia VA Medical Center, raising questions about whether still more cases are yet to be discovered.

The newly reported cases, forwarded to the U.S. Nuclear Regulatory Commission last week, mean that 98 men -- 86 percent of the total 114 patients -- got too much or too little radiation from the start of the Philadelphia brachytherapy program in 2002 until it was shut down in June 2008.

It was unclear yesterday why the new cases had not been found in the review that followed the closure of the program.

"The only thing we know so far is that they are reporting six events," said Viktoria T. Mitlyng, a spokeswoman for the commission, which oversees the medical use of radioactive materials.

The Department of Veterans Affairs, which has two weeks to file a full report, 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."

Still, the finding of new cases now raised concerns for some members of Congress.

"Why didn't they discover it sooner?" Sen. Arlen Specter (D., Pa.), said in an interview yesterday. "Did they deliberately withhold the information?"

U.S. Rep. John Adler (D., N.J.) said he was frustrated that the VA was still finding additional errors.

"These kind of mistakes are unacceptable, and it's time for the VA to conduct a systemwide review of its practices and programs," Adler said.

The VA did not respond to requests for comment about the new cases yesterday.

In brachytherapy, physicians permanently implant in the prostate from 50 to 100 tiny metal seeds that emit radiation over a 10-month period. If improperly placed, the seeds can damage nearby organs while delivering less-than-optimal doses of radiation to the prostate.

The seed implants are usually used to treat early-stage nonaggressive cancers confined to the prostate gland. Studies show that a brachytherapy patient who receives an optimal radiation dosage has about a 90 percent chance of cure.

Experts caution that just because a treatment is classified as a "medical event" under the NRC's definition -- as are the six newly identified cases -- it does not necessarily mean that the patient has been harmed or that the cancer will return.

Still, the VA's top radiation oncologist told a congressional panel last month that at least six veterans given seed implants in Philadelphia had developed prostate cancer.