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. The development of new types of therapy takes decades, and complex terminology is not always understood by the general public - and the question is in the air whether an effective cure for cancer has been found. Let's figure out why there cannot be one cure for all types of tumors and how far from traditional chemotherapy has oncology advanced now.
Why Cancer Is Not One Disease
Malignant tumors can develop from a wide variety of cells - from the epithelium of the skin to cells in the muscles, bones or the nervous system - and occur in many different places in the body. The basic knowledge of where the tumor originated and what it consists of allowed doctors to only 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 after a few years can return 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 localization, stage and tissue. If earlier breast cancer was considered one disease, now it is clear that it can be different - and the possibilities of treatment and the likely outcome depend on what receptors are on the tumor cells. The study of how cancer develops is far from complete - it seems like nowhere else the principle “the more we know, the more we don’t know” is at work. In addition, neglected, metastatic tumors remain a particular problem - they are much more difficult to treat than those detected in the early stages. But in the treatment of certain types of cancer, a revolution has taken place.
What is the problem with chemotherapy and radiation therapy?
Chemotherapy is the introduction of cytotoxic (that is, toxic to cells) substances, most often drugs are administered intravenously. They are designed to destroy rapidly dividing cells - and in addition to tumor cells, they also "get" to other tissues, where they multiply rapidly. It is the skin, mucous membranes and bone marrow in which blood cells are formed - therefore, typical side effects of chemotherapy include hair loss, stomatitis, bowel problems, and anemia.
In radiation therapy, the area where the tumor is located (or where it was before if it was removed surgically) is exposed to powerful radiation. This treatment can be done before surgery to shrink the tumor (then it will be easier to remove it), or after surgery in an attempt to destroy any remaining malignant cells. The main problems of radiation therapy are the same as those of "chemistry": firstly, even with the use of modern devices and techniques, it is impossible to completely protect healthy tissues from aggressive effects, and secondly, cancer mortality remains very high.
What is treated with hormone therapy
Hormone therapy for cancer was mentioned by Solzhenitsyn in his book Cancer Ward, 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, do exist - and for the best effect it is important to eliminate this influence. True, not hormones 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.
Such therapy is actively used for breast cancer in postmenopausal women or, for example, for prostate cancer in men. Breast cancer cells are often hormone sensitive, meaning they contain receptors that recognize estrogen, progesterone, or both. The presence of such receptors can be detected during a special analysis - and after that, medications can be prescribed that will block the receptors, preventing hormones from stimulating tumor regrowth.
When stem cells really work
Stem cells are often talked about either in the context of dubious rejuvenation procedures (we have already talked about why plant stem cells are added to creams), or as part of scientific achievements with loud headlines like "scientists have grown teeth from stem cells", but, unfortunately, not yet high practical value. But in malignant tumors of the bone marrow and blood, stem cells are used quite successfully.
For 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 precursors, which means that the blood will simply be deprived of cells and will not be able to perform its tasks. Therefore, after chemotherapy, transplantation is performed - the patient is injected with his own (obtained in advance) or donor stem cells. Of course, this method is not without problems - it is difficult to tolerate and is not suitable for all patients. Considering that the same multiple myeloma is considered a disease of the elderly (it usually occurs after 65-70 years), for many patients, treatment options are very limited.
What is targeted therapy
The further the oncological science develops, the more opportunities appear to influence drugs specifically, on a specific target (target in English) - and not on the whole body, as is the case with chemotherapy. Some tumors are characterized by mutations of specific, already known, genes, leading, for example, to the production of large amounts of some abnormal protein - and this helps the neoplasm to grow and spread. For example, if a mutation in the EGFR gene is found in lung cancer and a lot of a protein with the same name is produced, then the tumor can be fought not only with classical methods such as chemotherapy, but also with EGFR inhibitors.
Now there are drugs that are active in mutations of different genes characteristic of certain types of cancer. Patients are tested for these mutations to determine if it makes sense to use such a therapy: it is expensive and works well when the body has a target for it, but is useless if there is no target. Targeted drugs also include drugs that block angiogenesis, that is, the formation of new blood vessels that feed the tumor. Theoretically, hormonal and immunotherapeutic agents can also be classified as targeted - they are exactly what they act on certain targets, but for practical convenience they are usually placed in separate groups.
What was the Nobel Prize for?
Immunity is a powerful and complex system that not only helps to heal wounds or fight colds. Mutations occur every day that can cause a cell to divide uncontrollably and become cancerous; the immune system destroys these defective cells, protecting us from cancer. At some point, the balance may be disturbed, and this is not due to "reduced immunity", but to special mechanisms by which tumor cells "escape" from the immune response. The discovery of these mechanisms was the reason for the Nobel Prize for James Ellison and Tasuku Honjo - it formed the basis of immunotherapy, a new approach to cancer treatment.
The essence of immunotherapy is to make the immune system attack and destroy malignant cells on its own. Several drugs from this group have already been registered in different countries, and many more are in development. Allison and Honjo discovered immune checkpoints - molecules by which cancer cells suppress the immune response. There were drugs that suppress these molecules (called immune checkpoint inhibitors) and a revolution took place in oncology. For example, with melanoma (a disease with a 100 percent mortality rate 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 that are characteristic of a wide variety of malignant processes. For example, pembrolizumab is approved for the treatment of a variety of tumors, provided that they have a certain molecular feature associated with impaired DNA repair and increased tendency to mutation. Other drugs are used for one or two types of cancer - it all depends on the molecular target that can be acted upon by the drug antibodies. Finally, the most complicated immunotherapeutic method is CAR-T, in which a person's immune cells are "trained" to attack a tumor. The method has already been registered for the treatment of acute leukemia in children, due to its complexity and novelty, the cost of treating one person can reach half a million dollars.