COPENHAGEN, Denmark, Nov. 28 (UPI) -- Cancer survivors have more than double the risk of getting a second primary cancer of the same type than those who have not had cancer, Danish researchers say.
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.