Cancer cells are masters at hiding. Sometimes they can spread to other tissues or organs at an early stage and remain there undetected for a long time. But why is cancer so hard for the immune system to detect and why does cancer often come back after successful therapy?
The body’s defense system performs at its best every day. It fights invaders, repairs damage, and disposes of diseased and dead cells. With regard to cancer cells, the immune system faces a particularly difficult task. Because cancer cells are the body’s own living cells – and the defense system is not designed to fight its own body. In addition, the so-called programmed cell death mechanism is often disabled in cancer cells. Normally, diseased cells kill themselves.
Cancer cells can turn invisible
In addition, malignant cells have a variety of different strategies to hide from the immune system. Cancer cells can make themselves virtually invisible. In addition, cancer cells inhibit immune reactions and are thus more difficult to attack.
So-called tumor stem cells are a particular problem. These have the ability to divide indefinitely and keep forming new cells. Thus, a single cancer stem cell can in principle produce a complete tumor. Fighting tumor stem cells with cancer therapies is difficult. Cancer stem cells have good repair mechanisms and even have the ability to eliminate cell toxins, such as those used in the course of chemotherapy.
Why cancer often comes back
It can happen that chemotherapy or radiation therapy successfully fights the tumor, but a cancer stem cell survives. This can be dormant for a long time, sometimes for years, and at some point suddenly become active again. The cancer comes back. For this reason, recurrent cancer is in most cases a relapse, i.e. a flare-up of the same type of cancer. In addition, it can happen that a new cancer is due to the previous cancer therapy. In these cases, experts speak of a "second cancer".
To fight cancer, different therapies are often combined in treatment. This increases the chance of reaching and killing as many cancer cells as possible. The challenge is to design the therapy so that it is as aggressive as possible against the cancer, but causes as little damage as possible to healthy cells.
Every cancer therapy has its strengths
How the various therapy measures are combined varies from patient to patient. Among other things, it depends on the patient’s state of health, the type of cancer and the aggressiveness of the tumor. The operation is mainly used for localized tumors. A so-called systemic therapy, such as chemotherapy, which is effective throughout the body, can be used before surgery, for example to first shrink a tumor.
Both before and after surgery, chemotherapy can also launch a large-scale attack in the body against any remaining cancer cells – including those that have already spread to more distant tissues. Radiation therapy is usually applied locally in order to specifically treat the surrounding tissue, for example, in the case of breast cancer, the breast tissue and the lymph nodes located in the armpits.
Metastases: Even tiny tumors can sometimes spread
Usually not only the primary cancer is treated. If it is not known for sure whether the cancer has already spread, the therapy is often extended. Because not only larger tumors can form daughter tumors. With black skin cancer, for example, it can happen that even tiny tumors form metastases that are small at first and therefore go undetected.
It is even possible that a tumor discovered in the course of an examination is a daughter tumor and that the primary tumor is hiding somewhere in the body. A tissue examination provides clues. If the tissue found does not match the site where it was found, doctors know that cancer is also present elsewhere: For example, someone may have a bone tumor but it is made up of liver cancer cells because the cause (the primary cancer) is a tumor in the liver that has already spread to the bones.
The chances of healing are good for many types of cancer
Even if the facts so far do not sound very optimistic: The chances of curing cancer are much better today than they were a few years ago. An estimated 50 percent of all people with cancer survive it. Breast cancer and prostate cancer in particular, which are common cancers, are usually easily treatable.
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Of course, it would be even better if one could ensure that cancer does not develop in the first place. Colorectal cancer is an example here: Pre-cancerous lesions can be detected and removed during screening, so that cancer often does not develop in the first place.
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Important note: This information is in no way a substitute for professional advice or treatment by trained and accredited physicians. The content of t-online can not and must not be used to independently diagnose or start treatment.