Radiation Therapy

Radiation therapy uses high-energy particles or waves to destroy tumor cells while minimizing damage to healthy cells. More than half of all cancer patients receive radiation therapy as part of their cancer treatment, whether it’s used alone or combined with other treatments such as chemotherapy and surgery.

What Is Radiation Therapy?

Also referred to as radiotherapy, irradiation and X-ray therapy, radiation therapy is a localized cancer treatment, which means that it is aimed directly at the tumor.

Radiation therapy destroys cancer cells — via X-rays, gamma rays, electron beams or protons — by damaging their genetic material and preventing them from growing and dividing, which occurs at a faster rate than normal cells. Radiation may affect nearby cells, but this is usually limited and temporary. In contrast, cancer treatments like chemotherapy affect the whole body and may cause more body-wide damage to cells.

Additionally, because the DNA damage happens over time, radiation therapy doesn’t destroy cancer cells right away, but rather in the weeks or months after treatment.

Types of Radiation Therapy

The two categories of radiation therapy are external beam therapy and internal radiation therapy. When determining which to use in treatment, health care providers consider:

• Cancer type
• Tumor size
• Tumor location
• Proximity of tumor to healthy tissue
• Patient’s medical history
• Patient’s age
• Any other medical conditions the patient has
• Other cancer treatments

External Beam Radiation

During external beam radiation therapy, high-energy external radiation is aimed at the tumor by an outside machine called a linear accelerator. Different beams, such as photons, protons or electrons, may be used.

There are several types of external beam radiation therapies, as listed below.

3D conformal radiation therapy: This form of radiation therapy uses detailed images from computed tomography (CT), magnetic resonance imaging, or MRI, and positron emission tomography, or PET, scans to aim higher doses of radiation directly at the tumor. Treatment typically occurs once a day, Monday through Friday.

Intensity modulated radiation therapy (IMRT): More complex than 3D conformal radiation therapy, IMRT uses radiation waves of varying intensity to target the tumor and reduce damage to healthy tissue. Patients usually receive treatment once a day, Monday through Friday.

Image-guided radiation therapy: Doctors use repeated images taken before and during treatment to monitor changes in the tumor’s size and location and adjust the position of the radiation during the treatment process. Treatment schedules may vary, but patients typically receive this therapy once a day, Monday through Friday.

TomoTherapy: A type of IMRT, TomoTherapy, combines a CT scanner and an external beam radiation machine to take images of the tumor. It rotates during treatment, delivering radiation in a spiral pattern. Treatment is typically delivered once a day, Monday through Friday.

Stereotactic radiosurgery: This form of radiation therapy treats small tumors in the brain and central nervous system with high-energy beams. One example is Gamma Knife radiation. Patients may receive up to five doses, given once a day.

Stereotactic body radiation therapy: Similar to stereotactic radiosurgery, this radiation therapy is used on small tumors outside the brain and central nervous system. It may be used as an alternative to surgery and is administered once a day for up to five days.

Internal Radiation Therapy

Internal radiation therapy involves placing a radiation source inside the body, where it emits radiation over a period of time. When a solid source of radiation therapy — such as seeds, ribbons or capsules — is implanted near the tumor, it is called brachytherapy.

Systemic radiation therapy uses a liquid — given via a vein, an intravenous (IV) line or an injection — that travels throughout the body, finding and destroying cancer cells.

Radiation Treatment for Cancer

Radiation therapy may be used in a number of ways.

Primary treatment: Radiation therapy is often used to treat the cancer by preventing it from coming back, or stopping or slowing its growth before surgery.

Prior to surgery, or neoadjuvant: Radiation therapy may be used to shrink a tumor before surgery for easier removal.

Symptom relief: Radiation therapy may be used to help treat pain or ease symptoms, such as breathing issues and/or loss of bowel and bladder control due to cancer.

After surgery, or adjuvant: After surgery, radiation may be used to destroy any cancer cells that remain or to help relieve side effects.

Radiation therapy may also be used at the time of surgery. When radiation is used during surgery, it may be directed at the cancer without going through the skin.

While external beam radiation therapy is commonly used for many cancers, brachytherapy usually treats:

• Head and neck cancers
• Breast cancer
• Cervical cancer
• Prostate cancer
• Cancers of the eye

Thyroid cancers are often treated with liquid or systemic radiation therapy using radioactive iodine (I-131). Radionuclide therapy, or molecular radiotherapy, is another type of systemic radiation therapy that may be used to treat prostate cancer or gastroenteropancreatic neuroendocrine tumor, or GEP-NET, a rare cancer that forms in the pancreas.

In summary, radiation may be used before, during or after other cancer treatments, and it is sometimes combined with other treatments, such as chemotherapy or surgery. It may be used to treat cancer that comes back (recurrent) and cancer that has spread beyond the original cancer site (metastatic).

Lifetime Radiation Dose Limits

Radiation therapy is a critical cancer treatment tool, but safety limits must be followed regarding how much radiation an area of the body may receive throughout the patient’s lifetime. Radiation exposure from all sources accrues over time, including radiation from cancer treatments, diagnostic testing and radioactive materials in the environment.

Radiation Therapy Side Effects

Radiation therapy side effects vary based on the type, location and dose of treatment. Some radiation side effects develop during or right after treatment. Late side effects, such as heart or lung damage, may develop months or years after radiation therapy has ended.

Radiation therapy may cause the following side effects during or immediately after treatment:

• Fatigue 
• Hair loss 
• Skin changes 

Other radiation therapy side effects may depend on the body site being treated, such as:

• Blood in the urine (rectum or pelvis)
• Cough or shortness of breath (breast)
• Cramping (rectum or pelvis, stomach)
• Damage to the nerves in the arm or shoulder (breast)
• Diarrhea (rectum or pelvis, stomach)
• Difficulty passing urine (rectum or pelvis)
• Dry mouth (head and neck)
• Ear pain (head and neck)
• Fertility problems (rectum or pelvis)
• Frequent urge to urinate (rectum or pelvis)
• Headaches (brain)
• Hearing problems (brain)
• Heart damage, such as hardening of the arteries, heart valve damage or irregular heartbeats (breast)
• Jaw stiffness (head and neck)
• Lung damage, such as radiation pneumonitis, also known as inflammation of the lungs (breast)
• Lymphedema, which is swelling due to fluid buildup (breast)
• Mouth or throat sores (head and neck)
• Nausea, vomiting or loss of appetite (brain, head and neck, rectum or pelvis, stomach)
• Rib fractures (breast)
• Seizures (brain)
• Sexual challenges (rectum or pelvis)
• Sluggish thyroid gland (head and neck)
• Soreness, pain or tenderness (breast, head and neck)
• Speech difficulty (brain)
• Swallowing difficulty (head and neck, breast)
• Swelling in the gums or neck (head and neck)
• Taste changes (head and neck)
• Tooth decay (head and neck)
• Trouble with memory (brain)
• Urinary and bladder problems, such as pain or burning sensations (rectum or pelvis, stomach)

How to Reduce Side Effects of Radiation Therapy

Some ways to possibly ease side effects associated with radiation are listed below.

• Fatigue: Aim for at least eight hours of sleep per night, and get enough exercise during the day. Ask about prescription medicines that may help.
• Dry and irritated skin: Use prescription creams or mild, unscented soaps.
• Problems with sexual function: Ask about medicines to treat erectile dysfunction and vaginal dryness.
• Painful urination: Consume enough water throughout the day, and ask about prescription medicines that may help with the pain.
• Dry and painful mouth: Suck on lozenges, and try specialized mouth rinses to boost saliva production. Ask about prescription numbing medicines that may help.