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Medically reviewed by Dr. C.H. Weaver M.D. Medical Editor 4/2020

A “flu-like syndrome” is a collection of symptoms that are caused as a side effect of many cancer treatments, including some biological therapies and chemotherapy drugs. Symptoms are similar to the flu, and may include general aches and a fever. There is no single treatment for the flu-like syndrome; each symptom is managed separately.

  • What is flu-like syndrome?
  • What therapies cause flu-like syndrome?
  • What are the symptoms of flu-like syndrome?
  • How is flu-like syndrome managed?

What is flu like syndrome

A flu-like syndrome is a collection of symptoms that are a side effect of many cancer treatments. The exact process by which a flu-like syndrome is caused is not fully understood; however, it is believed that certain medications trigger a response from the immune system that is similar to the immune response triggered against the influenza virus or “flu”.

What therapies cause flu like syndrome

Cancer therapies associated with flu-like syndrome include:

  • Biologic therapies Ibritumomab (Zevalin®) Interleukin-2 (Proleukin®) Interferon alpha (Intron®) Sagramostim (GM-CSF, Leukine®) Rituximab (Rituxan®)
  • Chemotherapy drugs Asparaginase (Elspar®) Bleomycin (Blenoxane®) Cladribine (Leustatin®) Cytarabine (Cytosar-U) Dacarbazine (DTIC-Dome®) Procarbazine (Matulane®) Trimetrexate (Neutrexin®)
  • Supportive care Zoledronic acid (Zometa®)

What are the symptoms of flu like syndrome

Symptoms that commonly occur with flu-like syndrome include:

  • Fever (sudden onset associated with the therapy)
  • Chills (often occurs before the fever, usually involving upper body first)
  • Muscle/joint aches
  • Headache (usually across forehead, accompanied by sensitivity to light, may include visual disturbances, including blurred vision)
  • Poor appetite
  • Nausea, vomiting
  • Diarrhea
  • Runny nose (usually clear, watery and persistent)
  • Cough (dry, hacking, and persistent, rarely productive)
  • Bone pain
  • Fatigue (apathy, lack of energy or motivation)

Symptoms are often related to the dose of chemotherapy or biologic therapy, meaning a higher dose causes more symptoms, or more severe symptoms. Also, not all symptoms are present with each medication. Another aspect to these symptoms is they may be more severe at first but as the body “gets used” to the medication, the symptoms become less severe with subsequent doses. Symptoms may reappear or worsen if treatment is interrupted and then resumed or if the dose is increased. Symptoms resolve once treatment is discontinued.

How is flu like syndrome managed

Since flu-like syndrome is a collection of symptoms that may occur in different combination, there is no one “treatment”. Each symptom is managed separately. Some approaches used to manage these symptoms are listed below.

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Chills: A narcotic may be prescribed, such as meperidine (Demerol®) or hydromorphone (Dilaudid®), to stop severe chills that may occur with some drugs.

Diarrhea: The first drug to be prescribed for chemotherapy-related diarrhea is usually loperamide (Imodium® or others). Loperamide slows the gastrointestinal system and promotes the reabsorption of water from the GI system back into the body, thereby reducing the amount of fluid lost in the stool. Loperamide is effective for managing mild to moderate diarrhea, though its usefulness is limited for severe diarrhea. It is administered orally, is inexpensive and available without a prescription.

Fatigue: The reasons a cancer patient experiences fatigue are complex. However, anemia is a common side effect of cancer and cancer treatment and the most common symptom associated with anemia is fatigue. Anemia is an inadequate supply of red blood cells, resulting in a decrease in the oxygen carrying capacity of the blood. Fortunately, administration of the blood growth factor darbepoetin alfa (Aranesp® ) can increase the production of red blood cells, and constitutes an effective treatment for anemia and fatigue that is less risky than blood transfusions.

Fever: Fever and associated discomfort may be reduced with non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen (Advil®, Motrin®, etc). Adults may also use aspirin to reduce a fever. However, aspirin should not be administered to children as it may cause a rare, but potentially fatal disorder known as Reye’s syndrome.

If you have a bleeding disorder, you should avoid NSAIDs, as well as aspirin, because these drugs may prolong bleeding by interfering with the activity of blood platelets. Use of such drugs to treat fever should be discussed first with your healthcare professional.

Muscle/Joint aches, headache: Analgesics are often suggested to relieve mild muscle/joint aches and headaches. These include acetaminophen (Tylenol® and others) and ibuprofen (Advil®, Motrin®, etc).

Nausea/Vomiting: Drugs called antiemetics (anti-vomiting) can be used to block the signals from the brain that trigger nausea and vomiting. In this way, anti-emetics can prevent or decrease nausea and vomiting. The most sensitive signal during the first 24 hours after chemotherapy appears to be 5-HT3. Blocking the 5-HT3 signal is often used to prevent acute nausea and vomiting. Antiemetics that block 5-HT3 (5-HT3 inhibitors) are the most effective agents developed to date for preventing nausea and vomiting and are available to be administered orally or intravenously.

Although 5HT3-inhibitors are superior to other antiemetics, no antiemetic agents provide continuous control of nausea and vomiting when treatment is administered over two or more consecutive days. Most 5HT3 inhibitors do not control delayed nausea and vomiting when used alone or during the post-acute, delayed symptom phase. A newer antiemetic, called AloxiTM, may be more useful in controlling some delayed nausea and vomiting. 5HT3 inhibitors achieve greater control of nausea and vomiting when used in combination with steroids.

Other drugs commonly used to manage nausea and vomiting, either alone or in combination with antiemetics, include: