Cancer Cure: What Chemotherapy Is Replacing
Recently it became known that the Nobel Prize awarded to two scientists who made a discovery that led to a revolution in the treatment of cancer. Developments of therapies take dozens of years, and complicated terminology is not always clear to the general public - and the question has hung in the air whether they have found an effective cure for cancer. We understand why a single medicine for all types of tumors cannot be and how far oncology has already advanced from traditional chemotherapy.
Why cancer is not a single disease
Malignant tumors can develop from a wide variety of cells — from the epithelium of the skin to the cells of the muscles, bones, or nervous system — and occur in many different places in the body. Basic knowledge of where the tumor originated and what it consists of, allowed doctors to better plan operations — but it was unclear why in some cases cancer leads to rapid death, in others it is effectively cured, and in others it seems to disappear, but through few years can come back with renewed vigor.
Now the molecular mechanisms of tumor development are being studied more and more deeply - and it is already clear that it is impossible to classify them only by location, stage and tissue. If earlier breast cancer was considered a single disease, it is now clear that it can be different - and the type of receptors and possible outcome depend on the receptors on the tumor cells. Studying how cancer develops is far from its completion - it seems that here the principle “the more we know, the more we don't know” works anywhere else. Moreover, advanced, metastatic tumors remain a particular problem - it is much more difficult to treat them than those detected in the early stages. But in the therapy of certain types of cancer, the revolution did occur.
What is the problem with chemo and radiation therapy?
Chemotherapy is the introduction of cytotoxic (that is, toxic to the cells) substances, most often the drugs are injected intravenously. They are designed to destroy rapidly dividing cells - and in addition to tumor cells, it "gets" to other tissues, where they multiply rapidly. This is the skin, mucous membranes and bone marrow in which blood cells are formed - therefore the typical side effects of chemotherapy include hair loss, stomatitis, intestinal problems, anemia.
In radiation therapy, the area where the tumor is located (or where it was before, if it was surgically removed) is subjected to strong radiation. Such treatment can be carried out before surgery to reduce the volume of the tumor (then it will be easier to remove it), or after surgery in an attempt to destroy all remaining malignant cells. The main problems of radiation therapy are the same as in “chemistry”: firstly, even with the use of modern devices and techniques, it is impossible to fully protect healthy tissues from aggressive effects, and secondly, cancer mortality remains very high.
What is treated with hormone therapy
Cancer hormone therapy was also mentioned by Solzhenitsyn in the book Cancer Corpus, where it was said that female or male hormones are administered to treat certain tumors. Tumors, the growth of which depends on the influence of hormones, and the truth exist - and for the best effect it is important to eliminate this effect. True, it is not hormones that are used for this, but their antagonists — agents that suppress the synthesis of certain hormones or change the sensitivity of receptors to these hormones on cells.
This therapy is actively used in breast cancer in postmenopausal women or, for example, in prostate cancer in men. Breast cancer cells are often sensitive to hormones, that is, contain receptors that recognize estrogen, progesterone, or both of these hormones. The presence of such receptors can be identified in the course of a special analysis - and then prescription of drugs that will block the receptors, not allowing hormones to stimulate the re-growth of the tumor.
When stem cells really work
Stem cells are often spoken of either in the context of dubious rejuvenation procedures (we have already told why plant stem cells are added to creams), or as part of scientific advances with loud headings like "scientists have grown teeth from stem cells", but, unfortunately, so far not high practical value. But for malignant tumors of the bone marrow and blood, stem cells are quite successfully used.
In some types of leukemia and multiple myeloma, stem cell transplantation is an important component of treatment. High doses of chemotherapy destroy not only malignant blood cells, but also normal cells and their predecessors - which means that the blood will simply be devoid of cells and will not be able to perform its tasks. Therefore, after chemotherapy, a transplantation is performed - his own (obtained in advance) or donor stem cells are administered to the patient. Of course, this method is not devoid of problems - it is hard transferred and is not suitable for all patients. Given that the same multiple myeloma is considered a disease of the elderly (it usually occurs after 65-70 years), for many patients the treatment options are very limited.
What is targeted therapy?
The further the oncological science develops, the more opportunities there are to influence drugs with a sighting, on a specific target (target in English) - and not on the whole organism, as happens with chemotherapy. Some tumors are characterized by mutations of specific, already known genes, leading, for example, to the production of large quantities of some abnormal protein - and this helps the tumor to grow and spread. For example, if a lung cancer detects a mutation of the EGFR gene and produces a lot of protein with the same name, then the tumor can be dealt with not only with classical methods like chemotherapy, but also with EGFR inhibitors.
Now there are drugs that are active for mutations of different genes characteristic of various types of cancer. Patients are being tested for these mutations to determine if it makes sense to use this therapy: it is expensive and gives a good effect when the body has a target for it, but is useless if there is no target. Medication that blocks angiogenesis, that is, the formation of new blood vessels that feed the tumor, are also targeted. Theoretically, hormonal and immunotherapeutic agents can also be attributed to targeted ones - they are exactly what affects certain targets, but for practical convenience they are usually taken out into separate groups.
For what they still gave the Nobel Prize
Immunity is a powerful and complex system that not only helps to heal wounds or fight a cold. Every day there are mutations that can cause the cell to uncontrollably divide and become malignant; the immune system destroys such defective cells, protecting us from cancer. At some point, the equilibrium can be broken, and the reason is not "reduced immunity", but special mechanisms by which tumor cells escape the immune response. The discovery of these mechanisms was the reason for the Nobel Prize of James Ellison and Tasuku Honjo - it formed the basis of immunotherapy, a new approach to the treatment of cancer.
The essence of immunotherapy is to force the immune system to attack and destroy malignant cells. Several drugs from this group are already registered in different countries, and many more are in development. Allison and Honjo discovered immune checkpoints - the molecules through which cancer cells suppressed the immune response. There are drugs that suppress these molecules (they are called inhibitors of immune checkpoints) - and a revolution occurred in oncology. For example, with melanoma (a disease with a 100 percent mortality earlier), some patients managed to eliminate all signs of the disease - and these people have been alive for ten years.
Some of these drugs act on mechanisms characteristic of a variety of malignant processes. For example, pembrolizumab is registered for the treatment of many tumors, provided that they have a certain molecular peculiarity associated with a violation of DNA repair and an increased tendency to mutations. Other drugs are used for one or two types of cancer - it all depends on the molecular target, which can be acted upon by drug antibodies. Finally, the most complex immunotherapeutic method is CAR-T, in which human immune cells “train” to attack a tumor. The method has already been registered for the treatment of acute leukemia in children, because of its complexity and novelty, the cost of treating one person can reach half a million dollars.
PHOTO:tonaquatic - stock.adobe.com
