CHICAGO (CNS) -- Cardinal Francis E. George, retired archbishop of Chicago, has been dropped from the clinical drug trial to treat his cancer after scans showed the experimental treatment was not working for him, the Archdiocese of Chicago said.

Although the antibody drug was not effective on the cardinal, physicians overseeing treatment assured him that the information gathered during the trial will benefit others, the archdiocese said in a Dec. 31 statement.

Cardinal George was participating in a trial being conducting by University of Chicago Medicine, but remained under care at Loyola University Medical Center. He planned to meet with physicians at Loyola to discuss how to best address some of the side effects of the cancer.

The statement said cancer had not spread to any vital organs.

"He is at peace, but he counts on everyone's prayers that he might be of service to the Lord and his church in the time left to him," the archdiocese said.

Cardinal George was first diagnosed with bladder cancer in 2006 and had a recurrence of cancer announced in 2012. The clinical trial began in August at the University of Chicago and involved a drug designed to activate cells of the immune system, enabling them to attack cancer cells, the archdiocese said at the time.

After the cancer diagnosis, Cardinal George had surgery at Loyola University Medical Center to remove his bladder, his prostate gland and parts of his ureters.

Five years passed without a recurrence of the cancer, but in August 2012, doctors found cancerous cells in one of the cardinal's kidneys and in a nodule that was removed from his liver.

After the diagnosis, he underwent a series of chemotherapy treatments. Four months after being diagnosed, the cardinal was told that doctors could no longer find any sign of cancer. However, in March, Cardinal George announced in his column in the Catholic New World that the cancer had returned.

Cardinal George retired in September and was succeed by Archbishop Blase J. Cupich.