Acute promyelocytic leukaemia (APL) treatment and side effects

Patients with APL will begin treatment immediately. This is because of the high risk of severe bleeding if APL is left untreated.

The goal of your treatment will be to achieve remission. There are two levels of remission to be achieved before the disease is cleared:

Morphological remission

A morphological remission is also known as a complete remission (CR). This is achieved when the level of abnormal promyelocytes detected in your bone marrow is less than 5%. This will also be when your blood count has recovered to a normal level.

Molecular remission

A molecular remission is also known as a complete molecular remission (CRm). This is based on the results of your PCR tests (assessed from your bone marrow sample). The PCR test is very sensitive (it can detect one APL cell amongst 10,000 normal cells), so can identify remaining APL cells that aren’t visible under a microscope.

Achieving a negative PCR means that the test has been unable to detect any trace of the PML/RARA gene – in other words, APL cells cannot be detected by the most sensitive test available.

You won’t usually have a PCR test after your first cycle of treatment, because the test would likely be positive at this early stage (which is normal and does not predict your outlook). But you’ll have a PCR test after each further course of therapy.

Most patients (about 95%) achieve CRm by the end of their treatment.

The outlook for people with APL is generally better than for many other forms of blood cancer, although it still depends on a range of factors like age, general fitness, and the type of APL you have. Every person is individual, so your consultant and healthcare team are the best people to ask about your likely outlook (your prognosis).

Most patients with APL have a successful outcome and will achieve molecular remission with treatment. Up to three quarters of all younger, fitter APL patients are treated successfully.

Some rare types of APL are more difficult to treat, and so the outlook may vary. Your prognosis is also likely to be affected if you had a high white blood cell count when you were diagnosed. Your consultant will be able to tell you how these factors affect your outlook.

Talking about your prognosis

You may find it hard to ask or talk about your prognosis. Sometimes those close to you may want to know your prognosis even if you don’t. However, your healthcare team aren’t allowed to give this, or any other information, to anyone – not even family members – without your permission. Try to decide early on who you want to know about your condition, then tell your healthcare team – you can change your mind any time.

First-line therapy

First-line therapy means the treatment you’ll have after being diagnosed. If you’re diagnosed with APL, your treatment will be one of two drug combinations, described below. If first-line therapy is successful then it’s likely you won’t need any further treatment.

ATRA with arsenic trioxide

In 2018, a drug called arsenic trioxide was approved as an option for first-line treatment in England, Wales and Northern Ireland. It’s given in combination with another drug called all-trans retinoic acid (ATRA).

ATRA is given as a capsule. Rather than killing APL cells, ATRA targets the protein formed by the faulty PML/RARA gene. This allows APL cells to mature into normal white blood cells rather than cancer cells.

Arsenic trioxide works in a similar way to ATRA, and also targets this protein. It is given into a vein (intravenously). If your doctor recommends this treatment option, you’ll receive intravenous arsenic trioxide in combination with ATRA capsules for a number of weeks.

You may be worried if you’ve heard of arsenic before, as a poison when used in high doses. However, arsenic can also be used safely in medicine, and it is a very effective treatment for APL.

ATRA with chemotherapy

If you're receiving treatment in Scotland, or your condition is more advanced when you're diagnosed, you'll usually be given ATRA with chemotherapy, rather than arsenic trioxide.

If your doctor recommends this treatment option, you’ll start taking ATRA capsules as soon as APL is suspected. If you begin treatment but your diagnosis then changes after further tests, you’ll stop taking ATRA, but the ATRA you’ve already had won’t do you any harm.

ATRA works in combination with a group of chemotherapy drugs called anthracyclines. Anthracyclines can damage the DNA in cells and are especially effective against cancer cells. They are given to you through a drip (intravenously), usually into a vein in your arm. You may start on anthracyclines at the same time as ATRA or you may start a few days afterwards.

Clinical trials

If there is a clinical trial (study) available that’s suitable for you, your consultant may ask if you’d like to consider taking part in one.

Clinical trials are done for several reasons, including to look for new treatment options and to improve existing treatments. Taking part in a clinical trial has many advantages, such as the opportunity to have the newest available treatment which may not be given outside of the trial. You’ll also be very closely monitored and have detailed follow-up.

In a clinical trial, the best current treatment is compared to one that could be better. Your safety and well-being are always the first priority.

Taking part in a clinical trial does come with uncertainties, and you may prefer not to take part in one. Taking part in a trial is voluntary and you can choose to withdraw at any time. If you don’t want to be in a trial, or there isn’t a suitable trial available, you’ll be offered the best treatment available at that time which is suitable for your individual condition.

Second-line therapy

Most people with APL achieve remission through their first-line treatment. However, if you don’t, this is known as refractory APL.

If you have refractory APL, there are more treatment options available. These options can also be used if you relapse after being in remission. The treatment you have for relapsed or refractory APL will largely depend on what first-line treatment you had. 

ATRA with chemotherapy (if you had ATRA with arsenic trioxide as a first-line treatment)

If you have ATRA with arsenic trioxide as a first-line treatment and you don’t achieve remission or you relapse, your doctor may suggest you try ATRA with chemotherapy as a second-line treatment (see above for an explanation of ATRA with chemotherapy).

ATRA with arsenic trioxide (if you had ATRA with chemotherapy as a first-line treatment)

If you have ATRA with chemotherapy as a first line treatment and you don’t achieve remission or you relapse, your doctor may suggest you try ATRA with arsenic trioxide as a second-line treatment (see above for an explanation of ATRA with arsenic trioxide).

Other treatment options

Stem cell transplant

You might be offered a stem cell transplant (sometimes called a bone marrow transplant). This treatment aims to give you healthy stem cells, which then produce normal blood cells.

There are two types of stem cell transplant:

• an autologous transplant (or autograft) – this uses your own stem cells
• an allogeneic transplant – this uses stem cells from a donor.

If you’ve relapsed more than once or your doctor thinks you might be at risk of relapsing again after successful relapse treatment, you may be offered an autologous transplant, to prevent the APL from returning again. If you are going to have an autologous transplant, your own stem cells will be collected and stored (harvested) when you are in molecular remission.

An allogeneic transplant can also be very effective if you have refractory or relapsed APL. However, because it’s a higher-risk procedure, your doctors will only recommend this in particular circumstances – for example, if the PCR test result is still positive after you have finished your relapse treatment, or if the APL comes back after an autologous transplant.

> Order or download our booklet, The seven steps: blood stem cell and bone marrow transplants, for more information on stem cell transplants

There are some potential short-term and long-term side effects from treatment for APL.

Different people have different responses to their treatment. Even if two patients are having the same treatment, they may have a different experience. You might not get all, or even any, of these side effects – try to bear this in mind when you read about them. You may also like to talk about potential side effects with your healthcare team.

Side effects from treatment with ATRA or arsenic trioxide

Differentiation syndrome

Some patients treated with ATRA or arsenic trioxide will experience a condition called differentiation syndrome, also known as retinoic acid syndrome or RA syndrome. This can happen when ATRA or arsenic trioxide cause the APL cells to mature into white blood cells.

This is an important part of treating the disease, but when large numbers of white blood cells are present it can cause problems. It’s most likely to happen during the first 3 weeks of treatment of APL.

The signs and symptoms include a cough, difficulty breathing, fever, weight gain, fluid in the tissues and fluid in the membranes around the heart and lungs, which can cause a shadowing of the lungs on x-rays.

Differentiation syndrome can usually be treated with steroids. Your doctor may also recommend you stop taking ATRA/ATO for a few days.

If you have a high white blood cell count when you’re diagnosed, you may be at higher risk of differentiation syndrome. Your doctor may suggest you take steroids as a precaution to try and stop it happening.

Other side effects from ATRA with arsenic trioxide

If you’re having arsenic trioxide in combination with ATRA, you may experience some other side effects. Below are some more common side effects of arsenic trioxide:

• fatigue
• nausea
• vomiting
• diarrhoea
• dizziness
• muscle pain
• tingling
• rash or itching.

You should tell your doctor straight away if you notice one of the following side effects, as these may be signs of an allergic reaction:

• difficulty breathing
• fever
• sudden weight gain
• swelling (due to water retention)
• fainting
• feeling a strong heartbeat in your chest (palpitation).

Short-term side effects from ATRA with chemotherapy

If you’re having ATRA combined with chemotherapy, you may experience some short-term side effects from your chemotherapy treatment. These may include the following:

• an achy feeling
• constipation
• diarrhoea
• extreme tiredness
• infections
• rashes
• sore mouth/mouth ulcers
• nausea and vomiting.

You’re unlikely to have all of these. If you have side effects, do tell your healthcare team as they may be able to help with them – there are medicines you can take to help with nausea and vomiting, for instance.

Long-term side effects from chemotherapy

The long-term effects of chemotherapy depend on which drugs you take, the intensity of your treatment and, in some cases, the total amount of the drug you take. Your specialist will discuss these potential side effects with you before you start your treatment.

Anthracyclines can cause heart damage, more often in older patients. The level of damage caused to the heart, and the likelihood of you developing this at all, will depend on the amount of anthracyclines you need to take. If you relapse (the cancer comes back) and need more treatment, your healthcare team will consider what the most effective treatment will be for you, with the least possible side effects.

Infertility

You may be worried about the effect of your treatment on your fertility. It’s a concern that many patients have, and one that also affects their partners and families too. If you’re having treatment for APL at an age when you’re thinking about having children or more children, you might want to discuss your options for protecting your fertility with your doctor.

It’s very important that women don’t become pregnant while taking ATRA, arsenic trioxide or chemotherapy. If you’re sexually active whilst on treatment it’s recommended that you use at least two reliable forms of contraception.

Some chemotherapy drugs may have a temporary effect on fertility.

For men, chemotherapy drugs might affect sperm production and cause infertility. However, recent clinical studies have shown that most patients get normal sperm function back once they’ve finished chemotherapy.

For women, chemotherapy without radiotherapy is less likely to lead to infertility.

Permanent infertility is more common in patients who’ve had a stem cell transplant after high doses of chemotherapy and/or whole body irradiation, which are less common treatment options for APL.

It’s natural to worry about the effects of treatment on any children you may have after your treatment. Lots of evidence from clinical studies has shown that cancer treatment of a parent doesn’t lead to an increased risk of cancer or other health problems in their children.

The aim of follow-up is to look out for signs of relapse and treatment complications. These appointments are really important so do make sure you get to them.

For the first year after your treatment, you’ll normally have a check-up every one to two months. After one year, your check-ups will get less and less frequent, until they’re given every year at five years and onwards.

Your follow-up will also include regular testing of your bone marrow using a bone marrow aspirate, like you had when you were diagnosed. This will usually only be done if you were treated with ATRA and chemotherapy. 

A small number of patients who achieve a morphological remission will go on to experience a relapse. If you do relapse, there are a number of treatment options available. Your healthcare team will discuss the best way forward with you.

If you were treated with ATRA and arsenic trioxide, because your risk of relapse is very low, your doctors won’t normally monitor for relapse using a PCR test during your follow-up – as long as the test at the end of your treatment was negative.

If you’ve received ATRA and chemotherapy, because your risk of relapse is slightly higher, your doctors will monitor you using this test throughout your follow-up. The test means they’ll be able to detect a relapse early in most cases.

Treatment of patients at high risk of relapse

If your PCR test at the end of your final course of therapy shows any APL cells left in your bone marrow, you’ll need further treatment to prevent a relapse. The aim of this treatment is to achieve molecular remission, meaning that no APL cells are visible, even in a PCR test.

Types of relapse

Haematological relapse

If APL cells can be seen under a microscope at the time a relapse is identified, this is called a haematological relapse.  

Molecular relapse

When no APL cells are visible under a microscope but the more sensitive PCR test does reveal APL cells, this is known as a molecular relapse.

Extramedullary relapse

Although relapse usually occurs in the bone marrow, about 10% of all relapses are in places outside the bone marrow. This is known as an extramedullary (EM) relapse. Most EM relapses are in the central nervous system (CNS) – which involves the brain and spinal cord. It mostly happens in patients who had a high white cell count when they were diagnosed.

To test for CNS disease, your doctors will perform a brain scan and assess the fluid that surrounds the brain and spinal cord for APL cells. The procedure for this is called a lumbar puncture test.