When a fever appears during cancer treatment, infection is usually the first thing that comes to mind. But when blood tests show low inflammation markers, the medical team may conclude that a bacterial infection is unlikely. Families often find this more confusing, not less: if it is not an infection, then why the fever? In truth, body temperature does not rise from infection alone, and a body coping with cancer can run a fever through several different pathways.
It helps to understand what inflammation markers actually measure. The commonly mentioned markers include CRP (C-reactive protein), procalcitonin, and the white blood cell count. High values suggest a bacterial infection may be present, while low values make that less likely. However, low does not mean no cause. In the early hours of an infection the markers may not have risen yet, and a viral or non-infectious cause may not push them up much at all.
Cancer itself can generate fever, a phenomenon called tumor fever or neoplastic fever. Tumor cells and the immune cells reacting to them release fever-inducing substances (pyrogens) such as interleukin-6 (IL-6) and tumor necrosis factor (TNF), which act on the brain's temperature-regulating center and raise its set point. Tumor fever often comes without severe chills, the patient may feel relatively well for the temperature shown, and it is known to respond fairly well to non-steroidal anti-inflammatory drugs (NSAIDs).
There are many other non-infectious causes as well: a reaction to certain medicines or to a blood transfusion (drug fever), dehydration, blood clots (in the leg veins or the lungs), and, especially relevant in bile duct cancer, cholangitis from a blocked bile duct. When a bile duct is partly obstructed, a fever with chills can come and go, so watching the pattern of the fever matters.
At home, a fever diary is a powerful tool. Noting the time of day, how high the temperature climbed, whether chills, cold sweats, or pain came with it, and how far and how quickly the fever fell after a fever reducer, all help the medical team narrow down the cause. Contact the hospital promptly if the fever rises above 38.3C with shaking chills, or if there is confusion, a sharp drop in urine output, worsening jaundice, or a sense of falling blood pressure.
In short, a fever with low inflammation markers does not mean there is no cause; it is closer to a signal that a common bacterial infection is relatively less likely. Tumor fever, drug fever, dehydration, and cholangitis all remain worth checking, so recording the timing and pattern of the fever and working through the possibilities with your care team is the safest path.
This article is intended as general information and does not replace the diagnosis or treatment of any individual patient. Because the causes of fever and the right response differ from person to person, please discuss your situation with your own medical team.