Why is cancer so difficult to treat?
In many people's minds, cancer and AIDS are the two most horrific diseases. If you ask me, which one will be conquered first between the two? My answer is definitely AIDS.
Why so? Why is cancer so difficult to treat? There are three main reasons in my opinion.
The first reason is that cancer is an "endogenous disease" and cancer cells come from the patient itself, are part of the patient's body.
For "exogenous diseases", such as bacterial infections, we have antibiotics and the effect is very good. Why is antibiotics work so well? Because it is only toxic to bacteria and has no effect on human cells, and can be used at very high concentrations to kill all bacteria, while patients are “unscathed”.
But it’s not that simple to conquer cancer. Although cancer cells are broken human cells, they are still human cells. Therefore, to fix them, we are almost destined to be "to win at a great cost". This is the "side effect" that everyone often hears. For example, traditional chemotherapy drugs can kill fast-growing cells, which is useful for cancer cells, but unfortunately, many normal cells in our body are also growing rapidly, such as hair follicle cells under the scalp. Hair follicle cells are essential for hair growth. Chemotherapy drugs kill cancer cells and kill hair follicle cells. This is why patients with chemotherapy lose their hair. Hematopoietic stem cells responsible for hematopoiesis and maintaining the immune system are also killed, so the immune system of chemotherapy patients is very weak and extremely susceptible to infection. The epithelial cells of the digestive tract are also killed, so the patient has severe diarrhea, no appetite, and so on. Because of these serious side effects, chemotherapy drugs cannot be used in large doses, the concentration must be strictly controlled, and they cannot be used continuously. It is necessary to take a course of treatment. In fact, doctors constantly weigh and even compromise between curing cancer and maintaining the basic life of patients. If chemotherapy drugs can continue to be used in large doses like antibiotics, the cancer has long been cured. This is the main reason why I think AIDS will be overcome first than cancer. After all, AIDS is an "exogenous disease" caused by HIV. In theory, we may find drugs that only kill HIV without affecting human cells.
The second reason is that cancer is not a single disease, but a combination of tens of thousands of diseases.
There are no two identical leaves in the world, and there are no two identical cancers in the world. For example, lung cancer is the number one cancer killer in China and the United States. China now has nearly 600,000 lung cancer patients per year, and the United States has 160,000. I was often asked: is there any new medicine for lung cancer in the United States? I said: there are, but it is only useful for a small number of patients. For example, Novartis's latest lung cancer drug, Ceritinib, has recently been approved by the FDA, which has a good effect on 3% to 5% of lung cancer patients. But why did the new drug that was spent 10 years of research only work for a small number of patients? According to the pathological classification, lung cancer can be divided into small cell lung cancer and non-small cell lung cancer.
Is that the complete classification of lung cancer? No. We know that cancer is caused by genetic mutations. A recent systematic gene sequencing study showed that the average number of mutations per patient in lung cancer is close to 5,000! The combination of mutations varies from person to person, and each patient's genome is specific. The 600,000 lung cancer patients are actually more like 600,000 different diseases. Of course, this is not to say that we need 600,000 different drugs to treat lung cancer. Most of these thousands of mutations do not work for cancer cell growth. Only a few mutations are critical. As long as we capture these key genes, we are likely to develop more effective drugs. But in any case, new anti-cancer drugs developed by pharmaceutical companies, even if they are panacea, cannot cure all lung cancer patients. Going back to the question just now, why is Novartis' new drug, Ceritinib, effective only for 3% to 5% of lung cancer patients? Because Ceritinib targets the mutated ALK gene, only 3% to 5% of lung cancer patients have ALK mutations. For lung cancer patients without ALK mutations, the drug is completely ineffective. Ceritinib is currently preparing for clinical trials in China and expects that in the near future, Chinese patients with ALK mutations will be able to use this drug.
Because of the diversity of cancers, pharmaceutical companies are almost destined to develop drugs for only a few patients at a time. What is the development cost of each new drug? According to data, it needs at least 10 years and 2 billion dollars! Such a large amount of time and money investment has led us to make slow progress. To overcome all cancers, even if it is not in the foreseeable future, there is still a long way to go.
The third reason is that cancer can quickly develop drug resistance.
This is a common cause for cancer and AIDS, and it is the root cause of AIDS. Many people may have heard of super bacteria. Staphylococcus aureus infection is fatal before the onset of antibiotics, which can cause sepsis. But after humans discovered penicillin, Staphylococcus aureus was not so terrible. However, the evolution of biology is incomparably magical. Because we abuse penicillin, while it kills 99.999999% of bacteria, a certain bacterium suddenly develops new genetic mutations, which evolved resistance. They are no longer afraid of penicillin and become very dangerous. So, humans tried to find stronger antibiotics, such as vancomycin. But now there are both Staphylococcus aureus resistant to penicillin and vancomycin, which is super bacteria.
Biological evolution is a double-edged sword. Nature gives us this ability to adapt to different environments, but cancer cells not only retain the basic evolutionary ability, but also stronger. For the drugs we give it, the cancer cells are constantly changing, and try to avoid the drugs and survive. In Ceritinib clinical trials, people found that many cancer cells discarded the mutated ALK gene after a few months of treatment, and produced new mutations to help the cancer grow. The cancer cells evolve so fast. I cannot help thinking that how humans are insignificant in front of nature.