Fever of unknown origin might be a marker of occult cancer

Fever of unknown origin might be a marker of occult cancer, according to research published online by The Lancet Oncology.

Fever of unknown origin is characterised by a fever of more than 3 weeks’ duration, temperatures of more than 38.3°C and a failure to identify the origin of the fever. Underlying causes of these fevers are difficult to diagnose, but proposed causes are infections, cancers and collagen-vascular diseases. Henrik Toft Sørensen and colleagues hypothesised that patients with fever of unknown origin might have a higher risk of cancer than the general population.

To test their theory, they assessed 43205 patients discharged for the first time from Danish hospitals after treatment for fever of unknown origin from 1977-98. Using registry data, they examined whether these patients had a higher risk of subsequent cancer than that expected based on cancer incidence in the general population. They also compared survival of these patients with cancer patients without fever, but matched for cancer site, age at diagnosis of cancer and year of cancer diagnosis.

Within the first year of follow-up after discharge from hospital, patients with fever had an increased risk of developing cancer and 399 cancers were diagnosed (standardised incidence ratio 2.3 [95%CI 2.1-2.5]). This risk was highest for haematological cancers and sarcomas and, although reduced, the overall increased risk remained after 1 year of follow-up. Some cancer patients with fever also had a worse prognosis than did the controls without fever (mortality ratio 1.4 [1.2-1.6]).

Prof Sørensen states “Heightened diagnostic effort could account for some of the association; however, after several years of follow-up, diagnostic bias should not be a major contributing factor to the number of cancers recorded”. He continues, “Patients admitted to hospital with fever of unknown origin have an increased risk of developing cancer compared with the general population”.