NSAID test to distinguish between infectious and neoplastic fever in cancer patients

Fever of unknown origin (FUO) revised

Fever of unknown origin (FUO) was originally characterised in 1961 by Petersdorf and Beeson as a disease condition of temperature exceeding 38.3 °C on at least three occasions over a period of at least three weeks, with no diagnosis made despite one week of inpatient investigation. However, since underlying diseases are often reported for classical FUO, these presentations may not be considered to be of “unknown origin”. Rather, the aetiology of prolonged fever may resolve, or not resolve. The definition of fever with unresolved cause (true FUO) is difficult, as it is a moving target, given the constant advancement of imaging and biomarker analysis. Therefore, the prevalence of fever with unresolved cause (FUO) is unknown.

In this review, we report such a case of prolonged fever, which initially has presented as classical FUO, and discuss current literature. Furthermore, we will give an outlook, how a prospective study on FUO will allow to solve outstanding issues like the utility of different diagnostic investigations, and the types and prevalence of various underlying diseases.

[Fever of unknown origin in malignancies]

Fever is a common symptom in patients with malignancies. On the one hand it may be an (initial) symptom of cancer, on the other hand it may occur as a side effect of chemotherapy. Often a precise cause of fever can not be established and in these cases febrile temperatures >38.3 degrees C without proof of infection or relapse/progress of tumor is defined as fever of unknown origin. Especially hematologic neoplasias are accompanied by fever. Here, neoplastic fever must be distinguished from fever following immunosuppressive chemotherapy. In the latter severe infections due to neutropenia induced by cytoreductive chemotherapy is often identified as the cause of fever. These patients display a high morbidity and mortality, especially if an empiric anti-infectious treatment is not administered in time. A meticulous diagnostic work-up is therefore necessary, and until proven otherwise, an infectious cause must be considered and empiric antibiotic treatment initiated.

Diagnostic implications and clinical consequences of antipyretic therapy

It has been suggested that the response to antipyretic therapy might differentiate between fevers due to serious illness and fevers caused by less severe disorders; that neoplastic fevers are more responsive to nonsteroidal anti-inflammatory drugs than are infectious fevers; that the metabolic costs of fever can exceeds its clinical benefits; that antipyretic therapy can prevent or reverse febrile seizures in children and fever-associated mental dysfunction in frail elderly patients. This article examines the data on which these assertions are based.

Thermoregulation and the pathogenesis of fever

Infections, trauma, inflammatory processes, and some malignant diseases induce a constellation of host responses that are collectively referred to as the "acute-phase response." Elevation of core temperature is certainly part of the acute-phase response, and cytokines that raise core temperature in pathologic states are some of the same cytokines that account for other manifestations of the acute-phase response. This article examines fever as a part of the acute-phase reaction and the role of cytokines in thermoregulation.