Radiation therapy: What you need to know

Radiation therapy: What you need to know

Radiation therapy is a cancer and, less generally, thyroid disease treatment, blood disorders, and growths that are not cancerous.

A doctor can prescribe various stages of radiation for cancer. Radiation therapy can help reduce the size of a tumor in the early stages before surgery, or afterwards kill residual cancer cells. It may help to relieve pain as part of palliative care in the later stages.

One type of radiation treatment requires the use of a radiation beam generating system. The beam targets a particular body region. Another form involves either permanently or temporarily injecting a radioactive substance inside the body.

In this article, we focus mainly on radiation therapy as a cancer treatment.

What is radiation therapy?

What is radiation therapy?
Technicians administer external beam radiation therapy using a linear accelerator.

Radiation therapy uses energy waves, such as light or fire, for the treatment of cancers and other tumors. The form of radiation used in cancer therapy is a type of high-energy, called ionizing radiation.

Scientists still do not know exactly how radiation works as a cancer treatment.

However, they do know it breaks up cancer cells ‘ DNA in a way that interferes with their growth and division. In this way, radiation can kill cancer cells and prevent or stop the disease from spreading.

Sometimes a doctor prescribes radiation therapy alone, but in combination with other therapies, such as chemotherapy, surgery, or both, they generally recommend it.

There are many types of cancer. Learn more here.

Side effects

Radiation can affect both healthy and cancerous cells. A person experiences side effects when this happens.

Specific side effects depend on factors such as:

  • the area receiving treatment
  • the person’s overall health
  • the type and doses of radiation

Short term side effects

Short term side effects vary, depending on the part of the body receiving radiation.

They can include:

  • fatigue
  • hair loss
  • diarrhea
  • skin changes
  • nausea and vomiting

A 2018 study published in BMJ Open recommends screening for anxiety and depression in people undergoing radiation therapy and offering counseling services to those who may benefit from them.

Long term side effects

Long term side effects also depend on the treatment site.

They include:

  • heart or lung problems, if radiation affects the chest
  • thyroid problems, leading to hormonal changes, if radiation affects the neck area
  • lymphedema, which involves lymph fluid building up and causing pain
  • hormonal changes, including a possibility of early menopause, from radiation in the pelvic area

There is a slight chance that in some places, high doses of radiation may increase the risk of developing some form of cancer. A physician will provide more specific information and will help weigh the risks and benefits.

Not everyone who has radiation therapy experiences side effects over the long term. The risk is dependent on the doses, the treatment area, and other individual factors.

Radiation therapy and other treatments

Radiation therapy is one of several therapies used to treat cancer. These may be recommended separately or in combination by your doctor.

As well as radiation, a person may have:

  • surgery
  • chemotherapy
  • hormone therapy
  • targeted therapy

Among other things the treatment plan will depend on the type of cancer.

When a person receives combined radiation therapy and chemotherapy, the doctor can call this “chemoradiation,” which can lead to serious adverse effects.

Before surgery, once cancer is at an early stage, a person may have radiation therapy to reduce the size of a tumour. And, after surgery, they may be given it to help remove any remaining cancer cells.

Radiation only occurs in specific areas. When cancer has spread to distant parts of the body, it is least effective.

How effective is chemotherapy? Find out here.


There are two forms of radiation therapy.

External beam radiation therapy

This is the form which is most common. This requires an external machine releasing a radiation pulse entering the region of operation.

Depending on the need there are various forms available. For example, high-energy beams can target deeper cancer within the body.

Internal radiation therapy

There are various types of radiation therapy inside. These require the introduction or implantation of a radioactive substance into the body.

Brachytherapy consists of injecting a radioactive device into or around the cancerous tissue. The implant is either temporary or permanent. One form of internal radiation therapy involves drinking radioactive material or having an injection.

The goal is to restrict to what degree healthy tissue is exposed to radiation around the cancer. For example, doctors may recommend this treatment in case of prostate or ovarian cancer.

A doctor will recommend that you undergo all major types of radiation therapy. The decision depends on:

  • the type of cancer
  • the size of the tumor
  • the tumor’s location, including the types of tissue nearby
  • the person’s age and overall health
  • other treatments

Scientists continue to explore ways to improve radiation techniques with the least possible risk, in order to achieve more effective results.

What to expect

The doctor will explore radiation therapy and other treatments as well as assist in weighing pros and cons. They must assess the correct type and radiation dose before treatment begins.

Before treatment a person who receives external beam radiation can undergo a CT or MRI scan. This is to identify the exact location and tumor size. A doctor may make a permanent but small mark on the skin to make sure the radiation therapist is aiming the beam properly.

A person may need to wear a plaster cast or use a headrest or other device to make sure they stay quiet while being handled. A simulation may be the first session, in which the team runs through the process.

Many people have five sessions per week for 3–9 weeks, but this depends on specific factors. Each session lasts for around 15 minutes. Radiation therapy is painless, but there will be damage to surrounding tissue. This is why the treatment occurs on only 5 days per week. The 2-day break allows for some healing.

A person who has internal radiation therapy can need an anesthetic before the radioactive substance can be injected by the doctor. Ultimately, it can take several sessions, and some time at the hospital.

The methodological specifics depend on the type of radiation therapy and cancer type and location.


After receiving external treatment, a person can go home and continue with their daily routine.

However, they may experience:

  • tiredness
  • sensitivity around the treatment site
  • emotional distress

To help manage these effects, it is important to:

  • get plenty of rest
  • eat healthfully
  • talk to friends and family about any side effects
  • follow instructions, which may involve skin care, from the treatment team
  • avoid spending time in the sun, due to a risk of photosensitivity

In fact, track adverse effects and tell the doctor if they do occur. The doctor can prescribe additional treatments designed to alleviate these conditions.

People might need to discuss changing work schedules or taking medical leave with their employers.


Radiation therapy may help to shrink tumors in the early stages and kill cancer cells.

Together with other effective treatments, this kind of treatment will cause cancer to go into remission. It is not coming back again in several situations.

Radiation therapy, after cancer has spread widely, can also help treat symptoms. Radiation at this stage is part of palliative care, aimed at relieving the symptoms of a individual and improving their quality of life. It can, in some cases, also prolong a person’s life.

Treatment with palliative radiation usually involves lower doses and less therapy hours compared to curative care.

For example, in some people with bone cancer palliative radiation treatment can help to stop the growth of painful tumors.

Other methods that can assist in treating palliative radiation include:

  • relieving pressure or a blockage by reducing tumor size
  • treating symptoms of brain cancer, such as headaches, nausea, and dizziness
  • reducing symptoms of lung cancer, such as chest pain and breathlessness
  • controlling ulcerating tumors, bleeding, and infections

An obstruction in the superior vena cava may impair blood flow to the heart in people with head and neck cancers. Radiation therapy may help to relieve pain.

Cancer is metastatic when it’s spread to other body parts.


Many people are concerned about radiation therapy and feel anxious. It has different uses in cancer treatment, and in some cases, it can help achieve complete remission.

The National Cancer Institute (NCI) emphasizes that radiation can be costly.

Insurance covered individuals should speak about coverage with their insurer. Some agencies also provide financial support and other assistance to those needing treatment. The NCI sets out a list of options.

Speak to the doctor about any issues, and ask as many questions as possible. Understanding what to expect can contribute.


Will my hair grow back after radiation therapy?


Radiation therapy only causes hair loss at the site receiving the therapy. Hair loss may be temporary or permanent, depending on the site and the doses. Higher doses of radiation may be more likely to result in permanent hair loss. Seunggu Han, MD

Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.


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