Infection during or after cancer treatment

Having cancer or treatment for cancer can weaken your immune system. This makes it more likely that you will pick up an infection and develop a fever.

Chemotherapy

Chemotherapy is a type of anti cancer drug treatment. It travels around your bloodstream and works by killing cancer cells. 

Chemotherapy and infection

Chemotherapy drugs lower the level of white blood cells in your body. Your bone marrow produces these and they're important to help fight off infection. If your white blood cells are low, your immune system isn’t as good as it should be. This means you are more at risk of getting an infection.

Early symptoms of infection are usually easy to treat. If the symptoms are left, infections can worsen quite quickly. Simple infections can develop into life threatening sepsis within hours if not treated.

Your nurse, doctor, or pharmacist will tell you about the symptoms of infection to look out for. And they will explain when you need to call your advice line or return to the hospital.

Neutropenia 

There are different types of white blood cells. Neutropenia is when you have a very low number of white blood cells called neutrophils. These are particularly important in fighting infections. 

If you have neutropenia you are at risk of developing a serious condition called neutropenic sepsis. This can be life threatening. 

Neither you nor your doctor can tell whose fever could develop into a severe illness. So, all possible infections are treated urgently.

Not all chemotherapy drugs affect your bone marrow and increase the risk of infection, but many do. It depends on:

• which drug you have
• the amount (dose) of the drug – the higher the dose the more likely it is to affect your bone marrow
• your age – chemotherapy is more likely to affect your bone marrow function if you are elderly
• your general health
• the type and stage of your cancer

When are you most at risk?

Your risk of getting an infection is highest when your neutrophil levels are low. This is called the nadir. This usually begins around 7 to 14 days after each treatment. But the exact time can vary so ask your healthcare team when you will be at most risk. The levels usually return to normal between 21 and 28 days after your chemotherapy.

When your blood cell levels are at their lowest you can feel very tired. This is usually because it can also lower your red blood cells. Red blood cells are responsible for carrying oxygen around your body. You should feel less tired as your blood levels rise.    

You generally start to feel better again before your next treatment. Unfortunately, your blood cell levels go down again after each treatment. But once your treatment finishes, they return to normal levels.

Don’t be afraid to live your life as normal. You do not need to stop seeing family and friends unless they have an infection or feel unwell. You don’t need to avoid crowded places unless specifically advised to do so by your healthcare team. Infections during chemotherapy are usually caused by bacteria naturally present in your own body.

Growth factors for white blood cells

Your doctor might suggest injections of blood cell growth factors. 

These growth factors boost the number of white blood cells your body makes. The growth factor used in cancer treatment is granulocyte colony stimulating factor (G-CSF). Your doctor, nurse, or pharmacist will tell you more about this if you have these injections.

Radiotherapy

Radiotherapy uses x-rays to treat cancer cells. Radiotherapy destroys the cancer cells in the treated area. Healthy cells are also affected by radiation if they're in the treated area. 

Radiotherapy and infection

Radiation can also affect the cells in your bone marrow, which produce your blood cells, including the white blood cells. Generally, radiotherapy only affects the area being treated. It is less likely to affect your white blood cells compared to chemotherapy.

Who is most at risk?

Your bone marrow is more likely to be affected if you have radiotherapy to:

• a large area of your body
• the bones in the legs
• the chest
• the tummy (abdomen) or pelvis

You have regular blood tests during and after your treatment to check your blood cell count. 

Having chemotherapy with radiotherapy (chemoradiotherapy) can increase the risk of side effects, including having an infection.

Surgery

Infection is a possible side effect of any surgery or any procedure that involves cutting the skin. For example, having: 

• a biopsy
• a small tube to give intravenous fluids and chemotherapy (cannula)
• a central line

The risk of infection depends on what type of surgery or procedure you have. There is more of a risk with major operations, such as bowel surgery.

You might have antibiotics to reduce the risk of getting an infection after your operation or procedure.

Your nurse will check all your wound sites for infection regularly.

You might go home before your wound has fully healed. Your nurse will show you how to look after your wound. They will also give you the number of the advice line to call if you have any concerns.

Stem cell and bone marrow transplants

You might have a stem cell or bone marrow transplant as part of your cancer treatment. The stem cells are collected from the bloodstream or the bone marrow. 

Stem cells are very early cells made in the bone marrow. Bone marrow is a spongy material that fills the bones and is the body’s factory for making cells. These stem cells develop into red blood cells, white blood cells, and platelets. 

For the transplant, you have chemotherapy, sometimes with targeted cancer drugs. You might also have radiotherapy on the whole of your body. This is to try and kill off the cancer cells. 

This treatment damages your bone marrow. So you need a bone marrow or stem cell infusion to replace the bone marrow cells you’ve lost.

Transplants and infection

You have a low white blood cell count after your treatment. This means you are more at risk of getting an infection. This is most likely to be from the normally harmless bacteria we all have in our digestive systems and on our skin.

This is quite an intensive treatment so you usually have medicines to prevent infections. This includes antibiotics and anti fungal medicines. It’s also important that you follow the information from your medical team about diet and personal hygiene.

Graft versus host disease (GvHD)

Graft versus host disease (GvHD) is a transplant side effect that some people get when they have stem cells or bone marrow from somebody else.

GvHD can range from mild to very serious. Although it is not an infection, it often causes a fever. Treatments for GvHD, such as steroids and drugs which affect your immune system, can increase your risk of getting an infection.

Immunotherapy

Immunotherapy uses our immune system to fight cancer. It works by helping the immune system recognise and attack cancer cells.

Immunotherapy uses substances involved in fighting infection. When you get an infection the body produces cytokines. These help to control and direct the immune system to the infection. They are responsible for some of the symptoms of infection, such as fever.

When you have immunotherapy you get larger amounts of cytokines in your body than you would normally make. This seems to be the reason why symptoms such as fever can be a side effect of some of these cancer treatments.

Targeted cancer drugs

Targeted cancer drugs work by ‘targeting’ the differences that help a cancer cell to survive and grow. They are one of the main treatments for some cancers. For example, advanced melanoma and some types of leukaemia.

There are different types of targeted drugs. Some of these can affect your immune system, which means there is a risk of getting an infection. 

Your healthcare team can let you know if this is a risk with your treatment. 

Other possible causes of an infection

You are also at risk of developing an infection if you have:

• mouth sores
• skin rashes that you scratch and break the skin
• a tube of some kind in your body, such as a tube to drain urine from your bladder (a urinary catheter) or a central line
• chest conditions 

Coping

It can be worrying to think that your treatment puts you at risk of infection. It might help to remember that your healthcare team will monitor you and be aware of possible side effects.

You will have the number of an advice line and they will talk through what symptoms to look out for. It might help to talk to family and friends or someone in your healthcare team. Talking about any worries can help you to cope.

Remember early symptoms of infection are easier to treat. It's very important you tell your healthcare team about any symptoms straight away.