Does Radiation Therapy Weaken the Immune System?

Posted on December 2, 2022 in Radiation Therapy

Written by Dr. Kuremsky

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For many patients undergoing radiation therapy, their immune systems will not be affected by radiation therapy. This is because radiation is focused on specific targets in the body and can be designed to avoid the bone marrow which is where cells that make up the immune system are produced.

However, there are some patients undergoing radiation therapy who may be at an increased risk of infection due to the weakening of the immune system. This is more commonly seen in patients receiving concurrent chemotherapy or whose radiation treatment plan requires that larger volumes of bone marrow be exposed to radiation.

Here, we offer more insight into how radiotherapy affects the immune system and tips for improving your immunity during and after treatment.

How Does Radiation Therapy Affect the Immune System?

Radiotherapy uses high doses of radiation to target cancer cells. Though treatment is typically localized, healthy cells near the cancerous areas can sometimes be damaged too.

If stem cells in the bone marrow are damaged by radiotherapy, the body will struggle to produce white blood cells (WBCs). Also known as leukocytes, WBCs are responsible for attacking disease-causing pathogens like bacteria, viruses, parasites, and fungi.

When the white blood cell count is low – a condition called leukopenia – the body may be at an increased risk for infection.

Radiation Therapy and Immune System Risk Factors

The extent that radiation therapy affects your immune system depends on various factors, including:

  • The total radiation dose
  • The radiation schedule
  • Which part of the body is being treated
  • How much of the body is being treated

Higher radiation doses are more likely to cause severe side effects, including the potential for lessened immunity.

Radiation directed toward large portions of the bones is also more likely to compromise immunity since white blood cell production occurs in the bone marrow.

However, patients receiving radiation to their entire body (called total body irradiation) are at the highest risk for suppressed immunity. This treatment is only used in very specific cases, typically in preparation for a bone marrow transplant.

Radiation Therapy and Your Skin

Radiotherapy can also weaken immunity by compromising the body’s first line of defense: the skin.

The skin forms a physical barrier against germs. In specific circumstances, high doses of radiation can injure the skin by creating breaks in the skin or sores through which germs can enter the body. Your radiation oncologist may prescribe topical treatments to help reduce this risk of infection if you develop skin breakdown during the course of treatment.

Chemotherapy vs. Radiotherapy: Which Has a Greater Impact on Immunity?

Like radiation therapy, chemotherapy aims to target and destroy cancer cells. However, there are important differences between the two treatment options.

Whereas radiotherapy is localized to the area being treated with cancer, chemotherapy enters the bloodstream to reach the entire body, including the bone marrow. In some circumstances, chemotherapy can affect the production of white blood cells. Because of this, chemotherapy is often more likely to weaken the immune system than radiotherapy. However, if your cancer care team suggests a combination of both chemo and radiation therapy, then the risk for immune system suppression could be heightened.

Common Infections in People With Cancer

Patients receiving radiotherapy or who recently finished radiotherapy treatment are more prone to certain infections.

These infections are called opportunistic infections because they typically occur in individuals with compromised immune systems.

Opportunistic infections can be caused by bacteria, viruses, fungi, or protozoa. Common types of infections include:


Bacterial Infections

  • Staphylococcus (staph): Staph infections cause bumps, redness, and swelling on the skin. They are often mild and can be treated with antibiotics.
  • Streptococci (strep): Strep causes tonsillitis and cellulitis. Both are relatively mild and can be treated with antibiotics.
  • Enterococci: These bacteria can contribute to urinary tract infections, wound infections, a heart infection called endocarditis, and sepsis.


Fungal Infections

  • Candidiasis (thrush): Thrush causes white patches and soreness in the mouth. Your cancer care team may prescribe antifungal pills or an injection. Candidiasis can also cause vaginal thrush (yeast infection), which is treated with antifungal creams.
  • Aspergillosis: This fungus can cause a serious lung infection that must be treated with an IV drip.
  • Pneumocystis: The pneumocystis fungus can cause pneumocystis pneumonia, a severe lung infection that leads to fluid buildup. Oral antifungal medications are the typical course of treatment.


Viral Infections

  • Common Colds: If your immune system is compromised, a common cold can lead to bronchitis or pneumonia.
  • Herpes Simplex: This virus causes cold sores and genital herpes. There is no cure, but treatment can lessen symptoms.
  • Varicella Zoster (chickenpox): The chickenpox virus can cause potentially fatal infections in oncology patients. Luckily, there are antiviral drugs available.
  • Cytomegalovirus (CMV): Most people who contract CMV experience mild symptoms like fever and sore throat. But the virus can cause infections in oncology patients.
  • Influenza (flu): Cancer patients can develop life-threatening complications if they contract the flu.
  • SARS-CoV-2 (COVID-19): Oncology patients have an increased risk of contracting COVID-19. Vaccines and boosters can help mitigate severe illnesses.

How To Support Your Immune System During Cancer Treatment

To prevent illness while receiving radiotherapy, you must take certain precautions. These include:

  • Getting the flu shot each year
  • Receiving COVID-19 vaccinations
  • Washing your hands with water and soap especially prior to eating or preparing food
  • Wearing a mask in public
  • Avoiding sick people and large crowds
  • Social distancing
  • Avoiding unpasteurized dairy, cooking meat well, and washing produce
  • Treating cuts and scrapes properly

Your cancer care team may also suggest medications that help your blood marrow produce white blood cells which help to reduce the risk of infection

Immune System Recovery After Radiation Therapy

For most patients undergoing radiation therapy, the effects on the bone marrow will be minimal. However, for patients whose immune system is affected by treatment, the bone marrow may take several weeks to return to normal, and in rare cases, the impairment may be permanent.

Luckily, you can help your immune system recover by following common sense practices such as:

  • Eating a balanced diet rich in fruits and vegetables
  • Eliminating tobacco and avoiding alcohol
  • Limiting stress
  • Exercising regularly
  • Sleeping 7 to 8 hours per night

Next Steps

Asking for Support From Your Sero Cancer Care Team

At SERO, our expert radiation oncologists and care teams are here to help you navigate your cancer journey, from diagnosis to remission. This includes helping you understand how radiotherapy may affect your immune system.

Whether you have a question about boosting your white blood cell count or mitigating the risk of infection during treatment, we are here to provide kind and compassionate support.

To learn more about SERO and our radiation services, call us at 704-333-7376.