One of the lead investigators on the cancer studies, Dr. Anil Potti, was placed on administrative leave, said Douglas J. Stokke, a spokesman for Duke, while the university investigates allegations that Dr. Potti had falsely claimed that he was a Rhodes scholar.

The controversy erupted late last week after an article published in The Cancer Letter, a weekly publication for cancer specialists, reported that Dr. Potti, an assistant professor of medicine, had on occasion exaggerated his credentials. (A spokeswoman at Rhodes House at Oxford confirmed on Tuesday that Dr. Potti had not received the scholarship.)

When questions about Dr. Potti’s credentials became public, the American Cancer Society suspended payments of a five-year, $729,000 grant awarded to Dr. Potti to study the genetics of lung cancer. The society awarded the grant based in part on a résumé from the doctor that included the Rhodes honor, said Dr. Otis W. Brawley, the chief medical officer of the cancer society.

Dr. Potti did not respond to an e-mail message seeking comment.

In addition, several dozen biostatisticians and cancer researchers at Harvard, Princeton, Johns Hopkins and other academic institutions are now questioning the methodology behind the three clinical trials, urging a halt to the Duke studies — two on lung cancer and one on breast cancer — in a letter sent to the director of the National Cancer Institute.

The suspension of new patient enrollment in the three cancer studies at Duke comes just after Columbia said it was suspending research at a brain-imaging center there. Columbia halted its research after investigators from the Food and Drug Administration found that the center had routinely injected mental patients with drugs that contained impurities, an article in The New York Times reported last week.

The situation at Duke is different, however, because there are no allegations that patients were given deficient drugs. Dr. Potti had been featured in several promotional videos about research at Duke.

His research involves a prediction model in which genetic analysis is used to determine which chemotherapy drugs would work best for particular cancer patients. Dr. Potti and Dr. Joseph R. Nevins, a professor in molecular genetics at Duke medical school, developed the prediction model.

Some experts at other medical centers said they had been initially excited about the Duke researchers’ prediction model. Using that proposed system, a doctor should be able to examine tissue from a lung tumor, for example, assess the activity level of certain genes, and then choose the most appropriate treatment among a few standard chemotherapy drugs for a patient.

But the Duke researchers’ data analysis, published in influential medical journals like The New England Journal of Medicine and Nature Medicine, has come under increasing scrutiny by some outside experts.

Last year, two biostatisticians at the University of Texas MD Anderson Cancer Center published an article in the scientific journal Annals of Applied Statistics in which they identified errors in Duke’s data analysis and said they had not been able to reproduce Duke’s results.

“This list of errors is sufficiently long that we actually think this doesn’t work, and we told them that,” said Keith A. Baggerly, a co-author of that article and an associate professor of bioinformatics and computational biology at MD Anderson.

In this week’s letter to Dr. Harold E. Varmus, the director of the National Cancer Institute, more than two dozen biostatisticians and oncology researchers from academic institutions recommended ending the studies pending further outside review.

“Recently, published and peer-reviewed re-analyses of the work done by Potti and Nevins revealed serious errors that questioned the validity of the prediction models upon which these ongoing clinical trials are based,” the researchers wrote in a letter sent Monday.

If the studies continued without independent verification of the research, they wrote, patients might be assigned to improper drug treatments, potentially exposing them to health risks.

Duke had confidence in the outside analysis performed last year on the prediction model research, Mr. Stokke said. But, in light of the questions raised about Dr. Potti’s credentials, the clinical trial leaders decided on Sunday to stop enrolling new patients in the three cancer studies, pending a review of the data and science, he said.

The American Cancer Society also requested that Duke outline steps the medical center was taking to assure the accuracy and scientific validity of the research it sponsored, as well as inquiring about Dr. Potti’s credentials.