Chemo vs Radiation for Cancer Treatment

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Chemotherapy and radiation are among the most effective treatments to improve survival in cancer patients. While they both treat cancer, there are many differences between the two therapies, including how they work and their side effects.

This article will cover the differences between chemotherapy and radiation, the effects of each, and which one is harder on the body.

Chemotherapy vs. Radiation

Verywell / Jessica Olah

What are the Differences Between Chemo and Radiation?

With chemotherapy, drugs are given orally or through an intravenous (IV) injection. These drugs kill cancer cells or shrink or destroy a tumor. Chemotherapy can have effects system-wide, which means it impacts your whole body.

These drugs specifically damage and kill cells that grow quickly. They interfere with cells' ability to divide. Cancer cells grow uncontrollably and often much quicker than other tissues and cells in the body, so these compounds damage them. But some specific parts of the body have a fast turnover of new cells and are also impacted by chemotherapy medications, leading to side effects in parts of the body that are unaffected by cancer.  

Radiation also aims to shrink or destroy a cancerous tumor, but through a different process.

Radiation is a high-energy invisible light wave that can be directed at cancer cells to damage their genetic material, ultimately killing them. The radiation waves damage the cancer cells, which die over time and are removed by the body, causing the tumor to shrink.

Unlike chemotherapy, radiation is usually a local treatment, meaning it doesn't travel throughout your body. There are two types of local treatment: internal radiation and external beam radiation. The former is an injection of radiation in a solid or liquid into the tumor or nearby tissues. The latter involves an application of radiation from a beam generated by a machine outside the body. 

More rarely, radiation will be a systemic treatment (internal liquid radiation) given orally, through an IV, or an injection.

What Are the Benefits of Chemo and Radiation?

Both chemotherapy and radiation are effective and often essential treatment options for many cancers.

When cancer spreads, it can be challenging to treat. So chemotherapy is an important treatment option to help kill cancer cells that may have escaped the primary tumor and spread to other parts of the body but are too small to see; these are called micrometastases.

Chemotherapy can also help treat any tumor pieces or cells left over after other treatment approaches, like surgery or radiation therapy. 

On the other hand, radiation can successfully shrink or destroy specific tumors. Because this treatment doesn't have as many side effects as chemotherapy, it can be used as a replacement if you're unable to get chemotherapy due to certain medical conditions or other circumstances.

The treatment plan your healthcare provider comes up with will be specific to your type of cancer, as well as its stage and other considerations, like your age and general health. These factors play an important role in what treatments will ultimately work best for you and leave you with the best possible chance for survival.

Your healthcare provider knows your situation best, but feel free to get a second opinion from another healthcare provider by giving them access to your records and information. 

How Do Chemo and Radiation Side Effects Differ?

Both chemotherapy and radiation work to destroy cancer cells, which can take a toll on the entire body. But they may affect the body in different ways.

Many of the side effects of cancer treatment can be effectively managed or lessened. Palliative care (treatment to reduce the burden of symptoms) is an important part of any cancer treatment plan.

Side Effects of Chemo

Because the drugs used in chemotherapy can be nonspecific to cancers and impact other healthy tissues of the body, they cause some side effects. These side effects are typically limited to when you’re actively being treated with chemotherapy and will rapidly improve after treatment is discontinued.

Common side effects of chemotherapy include: 

Chemotherapy is often given in cycles. For example, you may receive one week of treatment and then have a few weeks off to allow your body to heal before the next treatment. 

Tell your healthcare provider about the side effects you’re experiencing and get holistic help from your care team to ensure your treatment goes as smoothly as possible. Your healthcare provider may be able to tweak your cycle schedule or dosage to help improve your side effects. 

In general, you can manage your symptoms by:

  • Taking anti-nausea medication
  • Staying hydrated
  • Taking short naps
  • Staying as active as you can
  • Eating small meals
  • Keeping your head covered so your scalp doesn't burn or make you too cold

If you’re worried about taking time off work, make sure to talk to your employer. Many employers are legally required to give time off work or adjust your workload or schedule while you’re undergoing cancer treatment. A social worker on your care team can help you navigate this sometimes tricky situation.

Side Effects of Radiation

Radiation typically targets one area, so with radiation you may experience fewer side effects than with chemotherapy, which is systemic. However, local radiation can have side effects if nearby healthy tissues are damaged during treatment. 

Side effects of radiation will vary depending on the location of the treatment, but they may include:

  • Exhaustion
  • Nausea
  • Mouth sores
  • Throat problems that make it hard to eat
  • Dry skin

Systemic radiation with an internal radioactive liquid can have more side effects throughout the body.

You'll likely feel pretty good when starting radiation treatment but feel progressively more run-down as your treatments continue, and even after they're done. Side effects from radiation should improve within a few weeks or months, but some may persist or show up in the longer term—months or even years after treatment.

Just like with side effects from chemotherapy, it's important to contact your healthcare provider about any effects you might be experiencing with radiation. Side effects will vary depending on the location of the radiation, but your healthcare provider can offer suggestions on how to cope with everything from eating issues to skin problems.

Fatigue is often the main side effect of radiation therapy, so it's best to rest as often as possible while your body fights cancer cells. Try to get more sleep at night and take short naps during the day when needed.

How Do the Risks of Chemo and Radiation Differ?

Both chemotherapy and radiation carry a risk of complications that include:

  • Fertility issues
  • Heart complications
  • Lung damage
  • Nerve damage
  • Infections

However, the chance of developing these complications varies depending on whether you're getting chemotherapy or radiation.

With chemotherapy, your risk depends on the specific chemo drug being used, the dosage, and the length of treatment. Because radiation is generally localized and not systemic like chemo, the risk depends on the dosage but also on the location of the treatment.

For example, people who receive radiation to the pelvis may have an increased risk of fertility problems. And people who receive radiation in the breast may have an increased risk of heart valve damage.

Which Is Harder on the Body: Chemo or Radiation?

It is difficult to say what cancer therapy will be more difficult for your body to handle. Different types and dosages of both chemotherapy and radiation will have different effects. 

These effects also differ depending on the person getting them. So, for example, someone on one treatment might have extreme nausea, while another might have extreme tiredness. 

A systemic treatment like chemotherapy or liquid radiation may have more off-target side effects than a local treatment. But local treatments that are administered only to the cancer site, like external beam radiation or solid internal radiation treatment, may have more extreme side effects in that area of the body. 

Ask your healthcare provider about what treatment options apply to you and how they could adjust these treatments or care for your symptoms if you have side effects.

Can Chemo and Radiation Be Used Together?

Some cancers can be treated with just radiation. These are most often cancers caught early—before they've grown large or started to spread.

Most of the time, cancer treatment plans will contain multiple treatments. These treatments can include radiation, chemotherapy, hormone therapy, surgery, targeted therapies, or immune therapies. When your healthcare provider combines multiple treatments at once, it’s called a combination treatment plan.

Combination treatments are used for many reasons. Treatments may be more effective when they’re combined. For example, chemotherapy may make radiation treatments more effective.

If your healthcare provider suggests undergoing one type of treatment before others, it’s called neoadjuvant treatment. Neoadjuvant treatments are typically used to shrink a tumor or destroy metastases before the primary tumor is surgically removed.

Treatments that come after others are called adjuvant treatments and are typically used to reduce the risk that cancers will return or spread after initial treatment or surgery on the primary tumor. 


Chemotherapy and radiation therapy are each used to treat cancer. The decision about which one is used depends on the type, location, and spread of the cancer. Chemotherapy is a systemic treatment, while radiation therapy is often a localized treatment but may be systemic.

Both can have side effects, which can differ by the patient and how the treatment is given. Whether one treatment is harder on the body than another will vary accordingly. Sometimes they are both used to treat a person's cancer.

9 Sources
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.
  1. National Cancer Institute. Chemotherapy to treat cancer.

  2. National Cancer Institute. Radiation therapy for cancer.

  3. National Cancer Institute. Definition of micrometastasis.

  4. Memorial Sloan Kettering Cancer Center. Managing your chemotherapy side effects.

  5. National Cancer Institute. Radiation therapy side effects.

  6. Yale Medicine. Managing side effects from radiation therapy.

  7. National Cancer Institute. Fertility issues in girls and women with cancer.

  8. American Cancer Society. How cancer and cancer treatment can affect fertility in males.

  9. National Cancer Institute. Combination treatments.

By Jennifer Welsh
Jennifer Welsh is a Connecticut-based science writer and editor with over ten years of experience under her belt. She’s previously worked and written for WIRED Science, The Scientist, Discover Magazine, LiveScience, and Business Insider.