Dr. Stig Bojesen of Herlev Hospital, Copenhagen University Hospital and the University of Copenhagen, and colleagues examined data for the entire population of Denmark -- 7.5 million people -- from 1980 to 2007 to determine whether the risk of secondary cancer is linked to the type of cancer found in the first instance.
About 10 percent -- 765,255 people -- had one or more diagnoses of primary cancer, for a total of 843,118 diagnoses, Bojesen said.
The study, published in the Canadian Medical Association Journal, found a 2.2-fold risk of a second primary cancer of the same type as the first in cancer survivors. About 15 percent of cancer survivors worldwide are diagnosed with a second primary cancer.
The risk of a different type of second primary cancer was 1.1-fold.
Risk varied depending on the type of cancer. The risk of a second cancer of the same type was reduced after prostate cancer and greatest after sarcoma.