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What Are Common Side Effects of Radiation Therapy?

Patients diagnosed with cancer may be treated with radiation therapy, which uses high-energy beams or radiation-emitting “seeds” placed within the body to kill cancer cells. This process is effective at treating many types of cancer, but it can also lead to bothersome and potentially distressing side effects.

Many patients scheduled to receive radiation therapy wonder, understandably, if they will experience an adverse effect. In this article, the expert oncologists and hematologists at Regional Cancer Care Associates (RCCA) discuss the risk of common side effects of radiation therapy – and how to mitigate them.

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What Is Radiation Therapy?

Radiation therapy, or radiotherapy, is a common treatment for many types of cancer, including:

Radiotherapy uses high-energy particles or beams to damage or kill cancer cells. Radiation is more precise and localized than other conventional cancer treatments, such as chemotherapy, that impact the body beyond the affected area. Radiation treatments are designed to cause as little damage as possible to healthy cells. Those cells usually recover and return to normal if they are damaged.

Still, radiation therapy can affect nearby healthy cells along with the cancerous cells it is targeting, and this can lead to side effects during or after treatment.

How Does Radiation Therapy Work?

Radiation therapy can both treat cancer and relieve its symptoms. The radiation damages the DNA of cancer cells, causing them to stop growing or die. This process does not happen immediately – it may take weeks of treatment before cancer cells start dying – but it does help treat cancer, prevent its return, and slow its growth. In some later-stage cancers, radiation can relieve side effects or pain; this is known as palliative treatment.

Radiation therapy is used alone or in conjunction with other types of cancer treatments, including surgery and chemotherapy. If a patient undergoes radiation before surgery, it can shrink the tumor so it is easier to remove. If it is used after surgery, it can help kill any cancer cells that were left behind.

Oncologists can also give patients radiation during surgery (known as intraoperative radiation). This technique delivers radiation straight to the cancer without passing through the skin, protecting normal tissue.

Types of Radiation Therapy

More than half of patients with cancer will receive some type of radiation therapy, the American Society of Clinical Oncology (ASCO) reports. There are three main types of radiation therapy. Some patients only need one type, while others may require more than one. These radiotherapies include:

External Radiation

External radiation directs high-energy rays from a machine directly into the tumor from outside the body. It can be administered over several weeks and can treat a variety of cancers, such as:

  • Brain cancer
  • Breast cancer
  • Colorectal cancer
  • Esophageal cancer
  • Head and neck cancer
  • Lung cancer
  • Prostate cancer

Oncologists can also use external radiation to relieve cancer’s effects by shrinking tumors that are causing symptoms.

Internal Radiation

Internal radiation therapy, also called brachytherapy, involves placing a radioactive substance (sometimes called “seeds” because of the small size of the radiation-emitting material) inside the body near the cancer. The radiation-emitting material is solid and can stay inside the body or be removed after a certain time. Internal radiation is often used to treat breast, prostate, lung, and other cancers.

Systemic Radiation

Systemic radiation uses radioactive drugs that attach to cancer cells and kill them. This type of radiation can be given orally or intravenously (injected directly into a vein).

Because the drugs are radioactive, patients must take precautions until the radioactivity subsides, usually within a few days (more on this below). Systemic radiation is commonly used to treat some types of thyroid cancer, advanced prostate cancer, and neuroendocrine tumors in the digestive system or pancreas.

The type of radiation prescribed will depend on each patient’s overall health, cancer type and stage, and ability to take any needed precautions. Patients should ask their medical team about the potential side effects of their prescribed type of radiation.

Common Side Effects of Radiation Therapy

Radiotherapy side effects can vary, depending on the type of radiation and body area treated. Some patients have more than one symptom, while others may have none.

Patients should note that medical advances are ongoing and making radiation delivery more precise, lowering the risk to healthy tissue and reducing the potential for side effects. Still, adverse effects can occur. Some of the most common are:


Fatigue is the most common side effect of radiation therapy, the National Cancer Institute reports. Fatigue typically is described as “feeling exhausted” and can intensify as treatment progresses. Some patients may also experience trouble sleeping and insomnia. This can worsen daytime fatigue and impair daily function.

Patients should get sufficient sleep, rest when necessary, and relax when possible during their treatment course. Doctors can often prescribe sleeping aids or give other recommendations to alleviate fatigue.

Lack of Appetite

Patients need to stay as strong and healthy as possible during cancer treatment, but this can be challenging when ongoing radiation therapy decreases appetite. Numerous studies suggest that radiotherapy can more than double the risk of malnutrition in cancer patients.

Patients undergoing radiotherapy should try to eat more frequent but smaller meals with nutritious foods high in protein and fat. Protein or nutrition shakes can also help patients stay nourished during radiotherapy.

Skin Problems

Skin problems also are common during and after radiation therapy. These skin effects, which include dry and flaky skin, itchiness, and easy burning in the sun, usually subside within a few weeks after the patient completes radiation treatment.

If radiation-related skin problems become bothersome, patients should use lotions or creams to soothe dry skin. They should also wear sunscreen and other sun protection when outside to protect against sunburn.

Stomach and Digestive Problems

Gastrointestinal (stomach and digestive) problems such as nausea, vomiting, and diarrhea also can occur. These symptoms are more common when radiation hits body areas close to the stomach, such as the pelvis, stomach, and rectum. Stomach problems often can be remedied or minimized by eating a healthy and balanced diet, taking anti-nausea medication, and staying hydrated.

Mouth Issues

Some patients may develop mouth issues during radiation, especially patients with head, neck, and brain cancers. These effects can include dry mouth, mouth sores, and changes in teeth and how food tastes.

Staying hydrated and chewing gum can help alleviate dry mouth, and eating soft foods and avoiding spicy and acidic foods can help relieve pain from mouth sores.

Other side effects of radiation therapy can include hair loss, memory or concentration problems, and sexual and fertility problems. The risk for these issues depends on the person’s cancer and the type of radiotherapy used to treat cancer. These side effects typically resolve once treatment finishes, although in some cases, they may last longer or even appear years after treatment.

Radiation Therapy Side Effect Management

For some patients, managing the side effects of both their cancer and cancer treatments can be difficult. The RCCA multidisciplinary team creates personalized treatment plans that include side effects management techniques and integrative care services. Patients also are encouraged to follow lifestyle recommendations for minimizing or avoiding radiation treatment side effects, including:

  • Eating a healthy and balanced diet
  • Staying active and exercising when possible
  • Staying in regular contact with the oncologist/hematologist and healthcare team
  • Getting counseling or finding a support group
  • Practicing stress relief and mindfulness tactics
  • Relaxing through yoga, massage, deep breathing, or acupuncture
  • Turning to friends and family members for help and support

Frequently Asked Questions About Radiation Therapy

Is radiation therapy safe?

Radiation therapy has been safely used for more than 100 years. Although patients are exposed to hazardous radioactive materials, radiation oncologists, therapists, and technicians follow strict safety regulations to minimize risk to patients. Also, the dose of radiation is as low as is reasonably achievable, or “ALARA,” while still being effective against the cancer.

Some patients are concerned about the risk of developing a second cancer from radiation. Although possible, this is very rare, and the benefits of curing the current cancer generally outweigh this small risk.

Is radiation therapy painful?

Radiation therapy is not painful. It cannot be felt, seen, or smelled while administered.

When do side effects of radiation appear?

Radiation side effects typically start during the second or third week of treatment and can last for several weeks after treatment ends. In uncommon cases, “late side effects” can develop long after radiation therapy finishes.

How long does a radiation treatment take?

While the length and frequency of external-beam radiation therapy will vary for each patient, treatment typically is given in a series over a few weeks. A single treatment generally takes less than 30 minutes, but it may need to be repeated every day or every several days for a few weeks or months.

Can patients continue working during radiation therapy?

That depends on several factors, including the patient’s overall health, cancer type and stage, the type of radiation administered, and how the radiation works. Some patients can continue working, while others cannot work while navigating side effects and treatment schedules.

Trust Your Cancer Care to RCCA

The expert oncologists and hematologists at RCCA offer patients with cancer access to cutting-edge, evidence-based cancer treatments and blood disorder treatments, including targeted therapy, immunotherapy, and hormone therapy. RCCA oncologists and hematologists see more than 26,000 new patients each year and provide care to more than 245,000 established patients, collaborating closely with their patients’ other physicians.

RCCA helps patients fight cancer in a comprehensive fashion, which is why RCCA patients also have access to:

RCCA also offers patients the opportunity to participate in clinical trials. These studies of investigational medications or new uses for existing agents offer qualifying patients access to an additional treatment option that may improve their outcomes.

RCCA has 22 conveniently located, community-based locations throughout New Jersey, Connecticut, Maryland, and the Washington, D.C. area. If you’re grappling with cancer or need a second opinion, request an appointment today.

we are here for you

For more information or to schedule an appointment,
call 844-346-7222. You can also schedule an appointment by calling the RCCA location nearest you.


Regional Cancer Care Associates is one of fewer than 200 medical practices in the country selected to participate in the Oncology Care Model (OCM); a recent Medicare initiative aimed at improving care coordination and access to and quality of care for Medicare beneficiaries undergoing chemotherapy treatment.