APL treatment and side effects

If your doctor thinks you have APL, you will usually start treatment while your doctor is doing more tests to confirm your diagnosis. This is because APL can cause serious complications such as bleeding.

The standard treatment for APL is a medicine called ATRA (all-trans retinoic acid). ATRA works by helping immature white blood cells develop into healthy blood cells. ATRA is usually given as a capsule or tablet. You will normally be started on ATRA as soon as your doctor suspects that you may have APL. You are likely to start having support with platelets and other blood products as soon as a diagnosis of APL is suspected.

If your results show that you do not have APL, the treatment you’ve already received will not have caused any harm. Your biggest risk is complications from bleeding or clotting, so it is important that you are treated urgently.

If you are diagnosed with APL, your hospital team will recommend a treatment plan and talk to you about what it will involve. Treatment plans are tailored to each person. The treatment you are offered depends on several factors such as your age, your general health, the type of APL you have and your APL risk.

We have more information about blood cancer treatment planning.

APL treatment is often divided into three phases. These phases are induction, consolidation and maintenance.

The aim of this treatment is to put you into remission (where there are little or no leukaemia cells left). During this phase, you will usually continue to take ATRA.

ATRA is combined with a medicine called arsenic trioxide (ATO). ATO is given through a drip into a vein (intravenously). You will usually be given this treatment for 8 weeks.

If you have been diagnosed high-risk APL, you will also usually have chemotherapy using a medicine called idarubicin (although other chemotherapy drugs are sometimes used). This is combined with ATRA and ATO. Idarubicin is usually given in 2 doses.

You may stay for long periods in the hospital with your hospital team close by during this phase. In some cases, your hospital team may recommend that you have some of this treatment as an outpatient. This is usually only when there is no longer any risk of bleeding complications or differentiation syndrome.

You will then have more rounds (or cycles) of treatment to clear any leukaemia cells that may be left after the induction phase.  This treatment phase also helps reduce the risk of APL coming back. You will usually be treated with a combination of ATRA and ATO during this phase even if you were diagnosed with high-risk APL.

You might be able to have some of these treatments as an outpatient, which means you won’t need to stay in hospital overnight.

Most people will not have this phase. Your hospital team may recommend maintenance depending on your risk of relapse. You are more likely to have this phase if you were diagnosed with high-risk APL. This phase aims to prevent APL from coming back (relapse). If you have maintenance treatment, you will usually have a combination of ATRA and ATO.

If you have a rare type of APL where the PML/RARA gene isn’t present, your treatment may be different from the standard treatment. Your treatment may also be different depending on other conditions you may have and your general fitness.

Your hospital team will recommend the right treatment for you and explain this to you.

You may have heard that arsenic is poisonous and be worried. Arsenic is only poisonous when used in high doses. The smaller doses of arsenic used in medicine are safe. Arsenic trioxide is a very effective treatment for APL.

Your hospital team may use some of the tests used to diagnose you to monitor you during treatment.

Side effects are the unwanted effects of blood cancer treatment. You might not get all, or even any of the side effects linked to the treatment you're having. Some side effects are temporary and will stop during or soon after you finish treatment. But others can last longer. Your hospital team will usually monitor you for side effects.

Side effects of APL treatments can include:

• headache
• dizziness
• muscle pain
• numbness or tingling
• rash or itching
• fast heartbeat
• low or high blood cell count
• fatigue
• feeling sick (nausea) and vomiting (being sick)
• changes in your liver function.

Differentiation syndrome (sometimes called retinoic acid syndrome or RA syndrome) is a serious complication of APL treatment.

APL treatment works by forcing leukaemia cells to mature into healthy white blood cells.

Sometimes this happens too quickly, and your body can struggle to cope. This is differentiation syndrome. It is more likely to happen during the first few weeks of treatment.

Symptoms of differentiation syndrome include:

• fever
• weight gain
• swelling (caused by fluid build-up)
• low blood pressure (hypotension) – this may cause you to feel dizzy or lightheaded
• difficulty breathing.

Differentiation syndrome is serious and must be treated quickly. Because it is more likely to occur during the first few weeks of treatment, you will usually be in hospital where your hospital team will be monitoring you. If you notice any symptoms, it is important to tell your hospital team straight away.

You will usually be treated with steroids if you develop differentiation syndrome. You may also receive a gentle type of chemotherapy to bring your white blood cell count down.

Your APL treatment may be stopped while you are being treated for differentiation syndrome. This is more likely to happen if you have severe differentiation syndrome.

If you’re having chemotherapy, usually with idarubicin, as part of your APL treatment, you may experience some side effects of this. Side effects of chemotherapy include:

• Feeling very tired (fatigue)
• feeling sick or being sick (nausea or vomiting)
• hair loss.

Many side effects of chemotherapy will usually go away after you finish your treatment. Tell your hospital team if you experience side effects as there are often things that can help.

Chemotherapy and other blood cancer treatments can affect people in other ways such as the ability to have children (fertility). If you wish to have children, you can ask about the fertility options available to you before you start chemotherapy. If you have high risk APL requiring treatment with idarubicin, you will usually need to start treatment straight away and there may not be time to consider fertility options.

We have more information about the side effects of blood cancer treatment.

We also have information about the late effects of blood cancer treatment.

ATRA may be harmful to a baby conceived or developing during treatment. You’ll need to use contraception to avoid becoming pregnant or fathering a child, while you’re having this treatment. It is important to let your hospital team know if you think you may be pregnant before you start treatment.

Supportive care can help prevent or manage problems caused by APL and its treatments.  You will need regular transfusion with blood products because of the risk of bleeding in APL. You will usually have the first ones as soon as your doctor thinks that you have APL.

You may have other treatments including medicines to prevent infections and to boost your immune system. You may also have medicines to treat side effects of APL treatment. If your hospital team think that your risk of developing differentiation syndrome is high when they diagnose you, you may be treated with steroids as soon as you start getting treated for APL.

Most people (between 90% and 95%) go into remission (where there are no signs of APL left) by the end of their first treatment.  In some cases, APL may come back after you went into remission after treatment. This is called a relapse.

In the rare cases where a relapse happens, this will usually occur within the first three years after you went into remission.  The risk of relapse is more likely if you had high risk APL.  If you had high risk APL, you will usually be monitored for 2 to 3 years after treatment, so a relapse is picked up quickly and treated. An early relapse (within 2 years) is very rare if you were treated with ATRA and arsenic trioxide.

In very few people, APL may not respond to treatment and may not go into remission. This is called refractory APL.

While this can be a worrying time, there are more treatment options available for you if you have refractory APL or you relapse.

The treatment you have usually depend on what treatments you have had first. You may have some of the same treatments you had when you were first diagnosed.

You may also have treatments such as:

• a stem cell transplant – this involves replacing the stem cells in your body with new, healthy stem cells. These can be your own (autologous) or a donor’s (allogenic) stem cells. This is usually given after high-dose chemotherapy if you are well enough for it.

• standard APL treatment alongside intrathecal therapy (ITT). This is if the relapse affects your central nervous system (CNS). This happens in around 10% of the people who get an APL relapse. It is more likely to happen if you were diagnosed with high-risk APL.

This information is accredited with the PIF TICK, the UK's only quality mark for trusted health information.

Last review February 2026. Next full review due February 2029. We may make factual updates to the information between reviews.

Thank you to Professor Steven Knapper and Carla Fitzpatrick, Clinical Educator for Haematology, for checking the clinical accuracy of this APL information.