Chemotherapy and radiation therapy are cancer treatments. They use different approaches to shrink tumors, kill cancer cells, and prevent cancer from spreading.

A cancer diagnosis can be life changing. Individuals with the condition may need to consider treatment options, including chemotherapy and radiation. Both these techniques aim to treat and cure cancer, but there are some key differences between them.

This article explores chemotherapy and radiation, possible side effects, and what to expect when someone receives these potentially lifesaving treatments.

Close-up of a person's hand propped on a cushion as they receive chemotherapy. They are wearing a green medical bracelet around the wrist.Share on Pinterest
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Doctors prescribe chemotherapy as the first line of treatment for a wide range of cancers. However, they may also use the term “chemotherapy” to refer to any medication to treat a disease.

In chemotherapy, doctors administer chemotherapeutic agents, a large group of drugs that can slow or stop the growth of cells. Most of them target fast-growing cells that divide and proliferate. However, they do not distinguish between healthy cells and cancer cells.

Many healthy cells in the body, such as those in the bone marrow, digestive tract, and hair follicles, grow quickly. Chemotherapy may also kill these cells, causing hair loss, a weakened immune system, and other health issues.

The goal of chemotherapy is to slow or stop cancer growth and prevent it from spreading to other areas of the body via metastasis.

There are various types of chemotherapy, each working slightly differently. Antimetabolites, for example, attack the parts of cells that allow them to synthesize DNA or RNA, and alkylating agents attack proteins in cancer cells.

Traditionally, doctors administered chemo through an intravenous (IV) drip at a hospital or clinic. Now, some chemotherapy drugs are available as pills.

Radiation can treat many cancers. Doctors use intense energy waves, such as X-rays or subatomic particles, to target rapidly growing cells and tissues. Like chemotherapy, it may kill healthy cells along with cancer cells. Healthcare professionals may combine radiation with chemotherapy to increase its effectiveness.

Radiation therapy falls into three broad categories:

  • External radiation: A doctor directs radiation from outside the body to target the tumor.
  • Internal radiation: Healthcare professionals place a radiation source inside the body to attack tumor cells. They may remove the implanted radiation later or leave it as most internal radiation forms become less radioactive with time.
  • Systemic radiation: An IV infusion or medication delivers radiation throughout the patient’s body.

With some early-stage cancers, radiation may be the first line of defense to prevent the disease from spreading. For other cancers, doctors may use radiation to shrink the tumor before surgery.

Sometimes radiation does not cure cancer but may help manage some cancer symptoms, especially if someone has terminal cancer.

Oncologists will decide which treatment would be best to treat an individual’s cancer. Additionally, chemotherapy and radiation can complement each other, and doctors may administer them together.

Whether someone has radiation or chemotherapy depends on the type of cancer and how far it has spread.

Overall, there is no evidence suggesting that one treatment is more effective than others in all or most cases. However, one technique may be a better option for certain types or presentations of cancer.

A 2018 study compared chemotherapy and radiotherapy after radical surgery in patients with cervical cancer and found no difference between these treatments.

A 2019 study tested the combination of radiation and chemotherapy for stage 3 or 4 endometrial cancer. Compared to chemotherapy alone, the addition of radiation did not increase the time between remission and relapse.

The right treatment depends on many factors. People with cancer can consult with their oncologist to discuss treatment options and the research that supports these recommendations.

Because chemotherapy and radiation damage both healthy cells and cancerous cells, the side effects are similar.

Some of the most common side effects include:

These side effects may be worse when someone has radiation and chemotherapy at the same time.

People may experience other side effects depending on the specific drug or treatment area. Brain radiation, for example, may cause temporary hearing loss, seizures, memory problems, and speech difficulties.

Both radiation and chemotherapy may increase the risk of developing other types of cancer. The specific risk depends on the drugs that doctors administer, how long a person undergoes treatment, and their other individual risk factors for cancer.

An oncologist may recommend using chemotherapy and radiation together, depending on a person’s diagnosis. Certain chemotherapy drugs can work collectively, although a person may notice more side effects.

People can talk with their doctor about the benefits of using chemotherapy and radiation to increase their chance of survival and likelihood of remission compared to the increase in side effects.

When and whether to use chemo or radiation depends on the cancer, the individual’s treatment goals, and other factors.

Sometimes, chemotherapy comes first, but this is not always the case. In some cases, a person only has radiation or radiation and chemo at the same time.

Every cancer is different, so there is no way to predict long-term survival or side effects based solely on its treatment. Some cancers have a high survival rate, while others can cause death in just a few months.

Factors to consider ahead of treatment include:

  • Side effects: The side effects of radiation and chemo are similar but vary from drug to drug and person to person.
  • Long-term survival: Both chemo and radiation may improve a person’s chances of recovering. Even when a cancer is terminal, a person may live longer with radiation, chemo, or both.
  • Doctor’s appointments: A person will need regular doctor’s visits to assess their progress. They may also require medical testing to consider how well their treatment is working.
  • Additional treatment: Chemo and radiation are not the only cancer treatments. A person may need surgery, medication to counteract the side effects of chemo or radiation, and other treatments.

Making cancer treatment decisions can be challenging. Ask a doctor about their recommendations and the research they draw upon when making those suggestions.

A second opinion from an expert can offer more insight and help a person know whether they are making the right decision for their needs, health, and treatment goals.