A fever indicates an elevation in core body temperature. While often associated with common infections, a fever can also be a symptom of cancer itself or a consequence of cancer treatments. Understanding the various reasons behind a fever in the context of cancer is important.
Cancer’s Direct Impact on Body Temperature
Cancer can directly cause a fever through several biological mechanisms, sometimes referred to as “tumor fever” or “paraneoplastic fever.” Cancer cells release pyrogens, which signal the brain’s hypothalamus to raise the body’s temperature. The immune system also responds to a tumor with an inflammatory reaction, producing cytokines that contribute to the fever.
Fever can also result from the breakdown of tumor tissue, which releases substances that trigger an inflammatory response. This direct effect of cancer on body temperature is a recognized paraneoplastic syndrome, meaning it is a symptom that occurs remotely from the tumor itself but is caused by the malignancy. Certain cancers are more commonly associated with this direct fever. These include lymphomas (Hodgkin and non-Hodgkin), leukemias, kidney cancer (renal cell carcinoma), liver cancer (hepatocellular carcinoma), ovarian cancer, and some sarcomas.
Other Common Causes of Fever in Cancer Patients
While cancer can directly cause a fever, it is often more commonly a result of other factors. Infections are a frequent cause of fever in cancer patients. Cancer and its treatments, such as chemotherapy, can weaken the immune system by reducing the number of white blood cells. This condition is known as neutropenia, and a fever in a neutropenic patient is considered a medical emergency due to the risk of severe infection.
Fever can also stem from the cancer treatments themselves. Chemotherapy and radiation therapy can induce fever as a side effect. Immunotherapies, including immune checkpoint inhibitors and CAR T-cell therapy, can also lead to fever. These therapies can activate the immune system, sometimes leading to an inflammatory response known as cytokine release syndrome.
When to Be Concerned About a Fever
For individuals with cancer or those undergoing cancer treatment, a fever warrants prompt medical attention. A temperature of 100.4°F (38°C) or higher, sustained for at least an hour, is generally considered a significant fever. It is important to contact a healthcare provider immediately if this threshold is met.
Additional concerning symptoms that, when accompanying a fever, necessitate urgent medical evaluation include chills or shaking, new or worsening pain, shortness of breath, cough, confusion, or severe headache. Even a normal temperature accompanied by a sudden feeling of being unwell should be reported to the care team. Self-treating a fever with over-the-counter medications without consulting a healthcare provider is not recommended, as it can mask a more serious underlying issue.