Leukemia is a general term that includes 4 main types. Two of them are chronic, namely chronic myeloid and chronic lymphocytic leukemia. 2 of them acute, namely acute lymphoblastic and acute myeloid leukemia. In medicine, one of the most important questions that need answering is what the outcome of such a patient is. This is referred to as “prognosis”, and the interpretation of the term differs between diseases. Prognosis usually includes the percentages of a complete cure, and those of death or long-term disability.
In cancers, only a few patients have a complete cure, defined as the elimination of all cancer traces, especially because cancer is a genetic disease. It is imprinted in your diseased cell genes. All treatment modalities aim at a “remission”, which is the elimination of all detectable cancer. If surgery is the method of treatment, we aim at the removal of a considerable portion or the totality of the tumor. Then, chemotherapy will do the rest for individual cells. In leukemias, however, things get a little more complex. The main cause of symptoms in leukemia is the change of blood components, whether by an increase or fall.
Therefore, to answer this question, we have to divide it according to the type of leukemia and then according to the severity of the disease, age and overall status of the patient, and whether this is the first time this patient has had leukemia or not. What is certain is that overall, leukemia patients nowadays have a much higher chance of survival than those who presented with the disease 10 years ago. The main difference between the cure rates of acute and chronic leukemias is their origin. Acute leukemias develop in immature cells of the bone marrow and develop a form of deformed cell that can easily be targeted by chemotherapy. Chronic leukemias, on the other hand, occur in more mature cells and are even detected during screening by an elevated number of a specific cell type usually present in the bone marrow. It is safe to say that, generally speaking, acute leukemias have higher rates of complete cure than chronic leukemias.
The question of cure, however, is misplaced in many cases. Medicine doesn’t always aim at a cure but at an improved quality of life for the patient which involves many parameters. For example, some cancers can theoretically be eliminated by a high enough dose of chemotherapy. But this high dose can cause more harm than good and even long-term disabilities for the patient, some can cause other types of cancers as well. A stark example of this is what we mentioned in our article of acute myeloid leukemia in the elderly who take a smaller dose of chemotherapy or a weaker chemotherapy regimen, which is less likely to bring remission, but this is still the best option to spare them the severe side effects of high-dose chemotherapy, which is more likely to be tolerated by the younger stratum of patients.
How can a genetic disease be treated?
Cancer originates within you, in your blueprint, and it doesn’t go away completely except if we remove the genes themselves or the cells containing them. Both of those options are done in blood cancers. Chemotherapy can be used to induce the cells carrying the genes to “kill themselves” and to remove the genetic defect. In chronic myeloid leukemia, this gene is well known, and it is called the BCR/ABL fusion gene. It is caused by a translocated genetic material between two clusters of genes called chromosomes. The main treatment of this type of cancer is a group of drugs called tyrosine kinase inhibitors or TKIs. The most famous and commonly used is imatinib. Surgery can’t be used in blood cancer, but we can remove the cells carrying the genes by another radical means called stem cell transplantation. Just like when we imagine burning down our houses when we see spiders roaming. A form of stem cell transplantation involves high-dose chemotherapy and/or radiotherapy to eliminate all cancer cells in the bone marrow, then implanting new ones. Another form may include other drugs or radiotherapy alone, which won’t kill all cells but will kill enough that the new bone marrow will take over and cure cancer.
Both of the above methods are not perfect and relapses of the cancer can occur, but they present the best effort and hope that we have in fighting cancer, and most research regarding leukemia involves perfecting both of these methods to ensure that we decrease the side effects and rejection rates of stem cell transplantation -which form most of its failures- and create new drugs to overcome the resistance of some cancers.
Acute myeloid leukemia: the young survive while the old perish
Acute myeloid leukemia is treated by chemotherapy and stem cell transplantation. The treatment is usually divided into two main stages, the induction and the consolidation phases. Induction phase includes chemotherapy, sometimes at a high dosage, which may be combined with other drugs collectively known as targeted therapy, including midostaurin and cladribine. After achieving good results detected by a blood counts, what usually follows is consolidation therapy, involving chemotherapy or a combination of chemotherapy and stem cell transplantation.
The doses of chemotherapy are likely to be too high, however. They may not be tolerated by some patients, especially seniors and those with an inadequate renal and liver functions. Actually, administering chemotherapy to these patients may be risky or even fatal. Stem cell transplantation is also a risky procedure due to the risk of rejection and life-threatening infections. The risk of failure of stem cell transplantation increases with age, so it may not be a good option for the old. The restriction of treatment options and the overall poor state of older patients make their cure less likely.
Acute lymphoblastic leukemia
Acute lymphoblastic leukemia is treated in a similar way to that of the myeloid type. It consists of induction, consolidation and maintenance chemotherapy, which may or may not follow. The main difference between the two types is the agent used and the method of administration. Cyclophosphamide, vincristine, adriamycin and prednisone combination is the usual regimen, also called CVAP. The other difference is CNS prophylaxis which is administering treatment to your brain and spinal cord because of their possible or established invasion with leukemic cells. Worth noting here, however, is that the presence of a Philadelphia chromosome in acute lymphoblastic leukemia in the past was a bad prognostic sign, which meant that people with that genetic abnormality were more likely to not respond to treatment and die, but with the advent of tyrosine kinase inhibitor drugs, the prognosis was changed for those patients, improving their outcome and life expectancy.
Chronic myeloid leukemia: the drug that changed everything
In recent history, chronic myeloid leukemia was treated in a manner similar to other cancers with intensive chemotherapy. As is the case with everything, we are afraid of what we don’t know, and our lack of knowledge regarding chronic myeloid leukemia made treatment options unclear. However, identifying the main genetic abnormality, “the Philadelphia chromosome” and the use of tyrosine kinase inhibitors, the first-generation drug imatinib, led to significant improvement in the outcome of such patients with over 94% of patients responding in the chronic stage. The term “chronic stage” signifies that this is the only stage easily treatable in CML.
The disease goes through three stages which are the chronic, the accelerated and the blast crisis. The blast crisis is the worst, most fatal and most resistant to treatment. Other agents are used for the blast crisis, but results are nowhere as positive as those achieved if the patient is “caught” during the chronic phase. The other main challenge facing the treatment of CML is the presence of resistance against this “magic drug”. Resistance can occur when the cancer modulates his defenses against the drug through changing its genetics, which the main target of this drug. However, several second-generation drugs were developed for this purpose. Stem cell transplantation remains a viable option with good results. It is safe to say that CML is the best managed type of leukemia to this day in its chronic stage.
Chronic lymphocytic leukemia: should we even treat?
Unlike other types of leukemia, chronic lymphocytic leukemia can remain without symptoms for years, and in such cases we don’t even have to treat patients. For this reason, we can say that chronic lymphocytic leukemia is the best leukemia to get. Its life expectancy exceeds its siblings and it rarely shows symptoms except late in the disease. What is even better is that the vast majority of patients are more than 60 years old. The only way chronic lymphocytic leukemia is treated is through stem cell transplantation. Nucleoside analogues include fludarabine, cladribine and pentostatin are the cornerstone of chemotherapy treatment of CLL. The gold standard in the treatment of chronic lymphocytic leukemia is fludarabine, and the most commonly used combination is fludarabine plus cyclophosphamide and rituximab.
Read also; How Long Can You Live with Chronic Lymphocytic Leukemia?
Other newer options include biologic agents, which target cancer cells more specifically than chemotherapy. But none of the previous treatment is given unless there is evidence of a rapid progression of the disease to spare the patient their side effects against a disease which is rarely cured and doesn’t cause symptoms. This practice is further proven by clinical trials which showed no benefit neither in the overall quality of life nor survival if chemotherapy is introduced early in the disease, and this example demonstrates how different the concept of quality of life is from simply curing a disease.