Chronic myeloid leukaemia
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Dr. Valentín García Gutiérrez. Hematology and Hemotherapy Service, Hospital Universitario Ramón y Cajal; Ramón y Cajal Health Research Institute; University of Alcalá
What is chronic myeloid leukaemia and whom does it affect?
Chronic myeloid leukaemia (CML) is a cancerous disease of the bone marrow characterised by an uncontrolled increase in the production of some of the cells it produces.
CML accounts for around 20% of all leukaemias, although it must be considered an infrequent disease, affecting approximately one person in every 100,000. The average age of patients when the disease appears is 56, its appearance during childhood being very infrequent.
The disease is included within a group of diseases known as myeloproliferative neoplasms, the common characteristic of which is their slow evolution.
In general it is diagnosed during an asymptomatic, and not very aggressive, stage of the disease called the chronic stage. Until the arrival of the drugs that are now used, the natural evolution of the disease was to remain in this chronic phase for a period of 3 to 5 years, after which the disease progressed to an accelerated phase, and then to a blastic phase. With the presence of these accelerated and blastic phases the disease is considered to have reached the most advanced stages, now being very similar to an acute leukaemia and consequently having a very poor prognosis. Fortunately, thanks to the treatments available, the probability of progression is less than 10%.
What are the symptoms and how is it diagnosed?
The most usual manner in which the disease presents itself is through the chance discovery of an alteration during a blood test. Such an alteration usually consists in a marked increase in the number of leukocytes (white blood cells) and/or platelets. Around 30% of patients with such alterations may suffer from generalised tiredness, weight loss, perspiration, bone pain, bleeding, repetitive infections, or abdominal problems resulting from an increase in the size of the spleen (splenomegaly).
Upon suspicion of the disease as a result of such a test a meticulous study must be made of the patient's blood and bone marrow to confirm the presence of the disease. Diagnosis is confirmed after the detection of the presence of a chromosome called the Philadelphia chromosome (named for the city in which it was discovered). This chromosome is usually studied by means of bone marrow puncture, aspiration and biopsy. As a complementary diagnosis, and one which will later be of use for evaluating the patient's response to treatment, an oncogene called BCR-ABL must be found (this test can usually be performed through a blood test, the blood being extracted in the usual way).
How is chronic myeloid leukaemia treated?
Present day treatment for CML consists of the administration of drugs called tyrosine kinase inhibitors (TKI) which, in principle, must be taken indefinitely. All TKIs are taken orally and have a very good toxicity profile.
Imatinib was the first drug to be approved for this disorder, being very effective and having an excellent safety profile. Nilotinib, dasatinib and bosutinib are the so-called 'second generation' TKIs, ponatinib is generally considered to be a 'third generation' inhibitor.
Both nilotinib and dasatinib are indicated for newly-diagnosed patients, and for patients for whom an insufficient level of control is achieved after treatment with imatinib (something that can happen with up to 40% of patients). Bosutinib and ponatinib are approved for patients who do not respond adequately to a second generation TKI. A small percentage of patients may develop a specific mutation called T315I, which confers resistance both to imatinib and second generation TKIs, making it essential to pursue treatment with ponatinib.
At the present time in Spain there is a generic imatinib on the market, produced by various pharmaceutical companies. All of them have demonstrated an adequate bioequivalence with the original brand (Glivec®) at a much reduced price. Since the beginning of 2017 almost all patients treated with imatinib are treated with one of the generic drugs available.
A bone marrow transplant, considered for many years to be the treatment of choice for most CML patients, is now reserved for patients who fail to respond to treatment with TKIs, something that occurs in less than 10% of cases.
Prognosis for chronic myeloid leukaemia
There has been a radical change in the prognosis for CML over recent years. After the arrival of TKIs, CML has changed from being a disease with a life expectancy of just 5 years for patients who are not candidates for a bone marrow transplant, to one with a life expectancy similar to that of the general population for those patients diagnosed during the chronic stage, (which is the case with the great majority of CML patients). At the present time, global survival rates for the disease are around 90%, most deaths occurring for reasons not related to the disease.
Nevertheless, there are some circumstances (the most important factor being the stage of the disease) which affect the prognosis and which must be evaluated by doctors in order to choose the most appropriate treatment.
Pregnancy and other special situations
Given the disease's excellent prognosis, and given that approximately 20% of diagnosed cases of CML corresponds to patients under the age of 40, the desire to conceive is an issue that is frequently raised.
The teratogenic effect of TKIs, that is to say, the risk of malformation, is unknown, it being recommended to avoid them during pregnancy and before gestation. Nevertheless, in the case of men, there is ever increasing evidence to suggest the possibility of treatment with TKI without there being any such teratogenic effect.
At the present time there is sufficient evidence of patients with CML who have had normal pregnancies after appropriate treatment for their disease.
It is essential for patients to raise the issue at a centre with experience in the matter so that the various options may be considered. Such options may include continuing with the administration of the drug (only in the case of men); interrupting its administration (temporally or definitively) for patients with an adequate response; or substituting the drug for another, such as interferon.
Chronic myeloid leukaemia and parenthood
Side effects of medication
TKIs are drugs that are generally well tolerated. During the first months of the disease patients frequently suffer from minor side effects, common to all of them, and which are generally transitory. The most adverse effects are nausea, water retention, abdominal discomfort and cramp. It is important for patients to know that some of the side effects may be asymptomatic and therefore only detectable by means of analysis and that it is, therefore, essential to monitor the disease closely. Most such side effects can be managed appropriately by means of reducing or interrupting the medication although it may occasionally be necessary to add a complementary treatment. It is of fundamental importance that patients should discuss any side effects with the doctor treating them and that they should make no changes at all on their own account. There are other specific side effects for each drug and the frequency with which they occur may depend on some of the patient's characteristics. The choice of treatment is therefore made on an case by case basis that is adapted to each patient
Despite their excellent safety profile, TKIs may interact with other drugs that patients need to take for other disorders. It is important for patients to consult with their doctors before starting a new course of medication.
Possibility of discontinuing the medication
Although, for the great majority of patients, the TKIs achieve an excellent control over the disease the general indication is to maintain the treatment indefinitely. However, there is now evidence of how, for a very select group of patients (who achieve a very high level of response), and after various years of treatment, it may be possible to safely discontinue the medication. This possibility for interrupting the treatment is even included in the prospectus for nilotinib. Nevertheless, it is of crucial importance that patients know that this interruption must only be for selected patients and under careful monitoring by specialised centres.
Links of interest concerning medical issues relating to chronic myeloid leukaemia
Links of interest about other general issues that may be of interest for patients with chronic myeloid leukaemia
Help and support
We recommend you contact the Spanish Association of Chronic Myeloid Leukaemia Patients (AELEMIC).
On our website you will also find the testimonies of people who are suffering, or who have suffered, from this disease. We would also like to invite you to follow us on our main social networks (Facebook, Twitter e Instagram) where we often share patients' accounts of overcoming the disease.
If you are resident in Spain, you can also contact us via email firstname.lastname@example.org so that we can help put you in contact with other patients who have overcome this disease.
You will find many other topics of interest about diet, fertility, treatments, etc., on our BLOG 'Unstoppable against leukaemia'.