Long-Term Side Effects of Radiation Therapy

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Concern over long-term side effects of radiation therapy is becoming more common, as survival rates improve. Just as there can be long-term side effects of chemotherapy, radiation therapy may result in side effects that may begin and linger far after treatment has been completed.

These can include heart problems, lung problems, thyroid problems, secondary cancers, and more, but it’s important to keep in mind that the benefits of these treatments usually far outweigh any risks. Many people will not experience any of these late effects.

Woman having radiation therapy
Mark Kostich / istock

Causes and Risk Factors

Radiation therapy works by damaging DNA in cells. This damage isn't isolated to cancer cells, though; normal cells can be damaged as well. While radiation therapy has improved significantly such that less damage occurs to healthy cells than in the past, some healthy tissues are inevitably exposed.

Several variables can increase or decrease your risk of developing long-term side effects of radiotherapy. Some of these are:

  • Your age at the time of radiation
  • The dose of radiation you receive
  • The number of treatment sessions
  • The type of cancer treated
  • The area of the body that receives radiation
  • Other cancer treatments, such as chemotherapy
  • Other health conditions, such as heart disease or diabetes

Advances of Radiation Therapy

Despite possible long-term side effects of radiation treatment, it's essential to point out that radiation therapy has come a long since it was introduced in 1903, especially in recent years. With more precise dosing and newer methods of delivery, older studies may overestimate the risks.

At the same time, as people are living longer with cancer, the long-term effects of radiation will become increasingly important. It's estimated that 50% of people diagnosed with cancer will receive radiation therapy at some point in their journey.

Long-Term Side Effects

Not everyone will have long-term side effects after radiation treatment. Many people will only experience some redness of their skin and fatigue at the time of treatment.

Even so, it's important to be aware of possible risks, such as heart disease, so you can be an empowered patient.


Hypothyroidism is one of the more common late effects of radiation therapy when radiation treatment involves the neck, head, and chest.

Immunotherapy drugs also increase the risk of hypothyroidism, so that those who have received both of these treatments should be extra aware of the possibility.

Radiation Fibrosis Syndrome

Radiation fibrosis can be thought of simplistically as the loss of elasticity in tissues after radiation, due to permanent scarring.

Many of the side effects below are caused by this fibrosis, which can occur in nearly any region of the body.

Pulmonary Fibrosis

Lung fibrosis is a permanent scarring of the lungs which can result from untreated radiation pneumonitis.

Radiation pneumonitis is an inflammation of the lungs which occurs between one and six months after completing radiation therapy to the chest and happens in roughly a fourth of people treated with radiation for lung cancer.

Since the symptoms can mimic symptoms of cancer or pneumonia, it's important to talk to your healthcare provider about any new respiratory symptoms.

Heart Disease

Heart disease is a very important and not uncommon long-term side effect of radiation therapy.

For example, in patients with Hodgkin’s disease who receive radiation therapy (not as common now), the leading cause of death is cardiovascular disease, not cancer.

Those at risk include people who have radiation to the chest, including radiation following a mastectomy for left-sided breast cancer.

Radiation can affect the heart in several different ways causing:

  • Coronary artery disease: Coronary artery disease caused by atherosclerosis can be a side effect of radiation.
  • Valvular heart disease: Radiation may result in damage to the heart valves.
  • Pericardial conditions: Conditions s such as pericardial effusions (a build-up of fluid between the tissue layers lining the heart) and constrictive pericarditis may occur.
  • Cardiomyopathy: This weakening of the heart muscle may occur, especially when combined with some chemotherapy drugs such as Adriamycin (doxorubicin).
  • Abnormal heart rhythms: These are called arrhythmias.

Symptoms of heart disease may not appear for years or decades following the completion of radiation treatment, so it's important to let your healthcare provider know if you have any chest pain or other symptoms suggestive of heart disease.

Newer techniques such as respiratory gating (controlled breathing designed to minimize the exposure of the heart to radiation) are becoming available and may lower the risk of heart-related complications.

Secondary Cancers

We have learned from atomic bomb blasts that radiation can cause cancer, and the doses of radiation given for cancer treatments may also pose this risk.

Blood-Related Cancers

Blood-related cancers such as acute myelogenous leukemia (AML), chronic myelogenous leukemia (CML), and acute lymphocytic leukemia (ALL) are a rare side effect of radiation therapy, most commonly in the past from radiation for Hodgkin's disease or breast cancer.

The risk peaks at 5 to 9 years after radiation treatment has been completed. Radiation may also damage the bone marrow resulting in myelodysplastic syndromes, diseases of the bone marrow which can, in turn, develop into acute leukemia.

Secondary cancers in survivors of Hodgkin lymphoma are relatively common, both due to the early age at diagnosis of many of these cancers and the high overall survival rate of the disease.

Unfortunately this increased risk has persisted despite improvements in radiation therapy, and may be related to the carcinogenic effects of chemotherapy drugs as well.

Solid Tumors

Radiation therapy may also increase later risk of solid tumors, especially thyroid cancer and breast cancer. Unlike blood-related cancers, the risk is highest 10 to 15 years or more after treatment is finished.

Cognitive Concerns

Radiation therapy, especially radiation to the brain, to the base of the skull, and to the neck may result in cognitive problems such as memory loss and difficulty concentrating.

Radiation oncologists now frequently treat people with a medication (one ordinarily used for Alzheimer's) during radiation therapy and this has been found to reduce cognitive problems later on.

Musculoskeletal Concerns

A number of different musculoskeletal concerns can arise years or decades after radiation.


Radiation may result in weakening of the bones, osteoporosis, and osteonecrosis. For example, radiation to the chest may result in the ribs becoming fractured more easily.


Radiation can affect the muscles and supporting structures of the musculoskeletal system resulting in restricted mobility, pain, and numbness.

Soft Tissue

Permanent darkening of the skin, telangiectasias (spidery red marks) and permanent hair loss may occur with radiation.

Radiation may also result in lymphedema, swelling that occurs as the result of damage to the lymph channels, for example, the arm swelling seen in some women who have had breast cancer.

Localized Symptoms

Radiation to the head and neck region can damage to the salivary glands and tear ducts. This damage may result in permanent dry mouth or dry eyes. Cataracts and dental decay may also be problems.

Radiation to the abdomen and pelvic regions may affect the:

  • Bladder
  • Colon
  • Pelvic organs

The result of this damage can be impotence and infertility.

How to Lower Your Risk

You can do a number of things in addition to the precautions your healthcare provider takes to reduce your risk of long term complications related to radiation therapy.

  • Don't smoke, as smoking increases the risk of lung cancer after chest radiation.
  • Talk to your practitioner about any new respiratory symptoms that may suggest radiation pneumonitis.
  • Ask about clinical trials designed to reduce the risk of late effects of radiation.
  • If you will be having chest radiation, ask if respiratory gating is available.
  • Ask your healthcare provider about physical therapy if your movements are restricted. Physical therapy can't rid your body of permanent scarring but can often improve flexibility and mobility.

A Word From Verywell

While there is the potential for a number of long term side effects related to radiation therapy, most of the time the benefits greatly exceed the risks.

Clinical studies are in progress looking at methods to decrease the risk of late effects of radiation therapy, many with promising results.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."