What’s the difference between chemotherapy and radiotherapy?

What is chemotherapy?

Cancer cells grow and divide in an uncontrolled way. Chemotherapy is when medicines are used to kill cancer cells. Sometimes it can get rid of all the cancer cells and cure the cancer. Other times, it helps slow down the cancer and stop it from spreading. Chemotherapy can damage healthy cells as well as the cancer cells, which leads to side effects.

Chemotherapy is usually given in cycles. You have a few treatment sessions, then a break so your body can recover. How many cycles you need depends on your type of cancer and other factors - your health care team will guide you through what’s best for you.

You can have chemotherapy on its own or with other treatments, like radiotherapy.

What is radiotherapy?

Radiotherapy uses high doses of radiation to kill cancer cells. It’s carefully aimed to protect healthy cells, but some may still be affected, causing side effects.

Treatment is given in small doses called fractions. Each fraction is one session of radiotherapy. How many fractions you need depends on your type of cancer and other factors - your health care team will discuss this with you. A planning session will happen before treatment begins.

There are different types of radiotherapy, and it can be combined with other treatments.

What’s the difference between chemotherapy and radiotherapy?

Chemotherapy and radiotherapy both target cancer cells, but they do it in different ways.

Chemotherapy uses drugs to fight cancer. You can take these drugs as tablets, injections, drips, or creams. The drugs travel throughout your body.

Radiotherapy involves using high doses of radiation. The radiation is directed to the area that has cancer. This can be done externally using a machine that releases radiation onto the outside of the body. Or it can be done internally, by putting radioactive material inside the body.

Why are chemotherapy and radiotherapy used together?

When chemotherapy is used alongside radiotherapy, it’s known as chemoradiotherapy or chemoradiation. Using the treatments together can be more effective than using them on their own.

Chemotherapy drugs can boost the response of cancer cells to radiotherapy.

You may get chemoradiation for some types of cancer. You might have it:

• as a main cancer treatment
• to treat cancers that cannot be removed with surgery
• to shrink a tumour before surgery (neoadjuvant)
• after surgery, to reduce the risk of the cancer returning (adjuvant)

What determines if you get chemotherapy or radiotherapy?

Chemotherapy and radiotherapy are just two types of treatment. Other treatments may also be used such as:

• hormone therapy
• immunotherapy
• targeted therapy
• advanced therapies
• surgery

Your doctor will choose the best combination based on your individual case and the latest evidence.

The type of cancer treatment you’re offered depends on several factors such as:

• the type of cancer
• how big the cancer is
• where the cancer is and whether the cancer has spread
• changes in your own genes or in the cancer’s genes
• the evidence behind each treatment
• your general health

You can discuss this with your doctor and other healthcare professionals to create a treatment plan that is best for you.

What are the side effects of chemotherapy versus radiotherapy?

As healthy cells are damaged, both treatments can cause short and long-term side effects. Here are the most common side effects.

Chemotherapy can cause side effects such as:

• tiredness
• feeling or being sick
• diarrhoea
• hair thinning or loss

General radiotherapy side effects can include:

• tiredness
• skin reactions
• effects on your sex life and fertility
• problems with eating and drinking

Some side effects might occur in the part of your body that receives radiotherapy.

Some people may have mild side effects, but others may have more severe ones. Your healthcare team will help you to cope with and reduce them.

How long does it to take to recover from chemotherapy and radiotherapy?

Recovery after cancer treatment can take weeks, months, or even years. There’s isn't a set recovery time. You may have ongoing side effects and emotional challenges to cope with.

After your treatment, you’ll usually speak with your healthcare team. They can offer support and discuss what to expect after treatment for cancer ends. To aid your recovery you might find it helpful to set yourself small goals. You could try light exercise, eating well, or restarting hobbies.