Prolonged Fever Can Be Sign of Some Cancers

A fever of unknown origin can sometimes be a sign of cancer, including lymphoma, kidney and liver cancer, according to a new Danish study.

Such a fever is one that lasts more than three weeks with temperatures above 38.3 degrees Celsius (about 101 degrees Fahrenheit), with an unidentifiable cause. Patients with these fevers appear to be at a slightly higher risk of cancer, according to the report.

"We found an association between fever and cancer," said study author Dr. Henrik Toft Sorensen, a professor of medicine in the Department of Clinical Epidemiology at Aarhus University Hospital, in Denmark.

However, "the absolute risk is very low. Much lower than reported in other studies," he added.

The new research appears in the Sept. 28 online issue of The Lancet Oncology.

Previous studies had shown an association of fever and cancer of 20 percent to 30 percent, Sorensen said. "But we found very few cases of cancer related to fever compared with the incidence of cancer in the general population," he said.

In their study, Sorensen and his colleagues collected data on 43,205 patients who had been treated in Danish hospitals for fever of unknown origin from 1977 through 1998. During more than six years of follow-up, the researchers compared the incidence of cancer among these patients with the general population.

They found that patients with fever were at a 2.3 percent increased risk of developing cancer. After one year, the risk was highest for cancers of the blood, and cancers of the liver, brain, and kidney.

In addition, more of the people diagnosed with cancer had cancer that had spread to other organs, compared with patients who didn't have a fever. The increased risk continued after one year, but at a lower level, the researchers noted.

Some cancer patients with fever also had worse outcomes, including a slight increase in mortality compared with other cancer patients.

Because the increased risk of cancer associated with fever is slight, Sorensen doesn't think there needs to be extensive cancer workups for patients with fever. "You probably do not need to look for cancer and do a lot of tests in a patient coming into a hospital with fever of unknown origin, because your risk of cancer is very low."

One expert thinks the finding concerning fever-related cancers may reflect better diagnosis of fever and better cancer diagnoses.

"We know some cancers are associated with fever," said Dr. Yelena Novik, an oncologist at New York University Cancer Institute and an assistant professor of oncology at New York University School of Medicine.

There are still some cases of fever of unknown origin that may be a sign of cancer, Novik said. "But we are probably better at diagnosing fever and cancer better," she said.

Novik advises that if you have a fever of unknown origin, it should be checked, including a screening for cancer. "Don't let the fever go on," she said. "Make sure all the possible causes for the fever have been explored."

More information

The American Cancer Society can tell you more about detecting cancer.