13 September 2022

Check Up #6 - Chemotherapy, radiotherapy, targeted therapy and immunotherapy

What does each of them do?

Check Up #6 - Chemotherapy, radiotherapy, targeted therapy and immunotherapy.

Chemotherapy is the most conventional treatment against cancer. It uses medication to kill cells, and in particular cancer cells. But it does not target cancer cells specifically. It can be used by itself or in combination with other treatments, such as radiotherapy (see below) or surgery, to make them more effective.

Chemotherapy is usually administered intravenously at a hospital in the course of several sessions, but it can also consist of tablets taken at home. It can include one drug or a combination of drugs.

Since it is not only toxic to cancer cells, it has a range of well-known side effects, such as hair loss, vomiting, and tiredness. Today, there are other medications available to deal with much of these unpleasantness.

Radiotherapy is a cancer treatment that uses high doses of radiation to attack a cancerous tumor. This kills cancer cells or damages their DNA, thus slowing their replication and shrinking the tumor. It is by definition a local treatment; it does not affect the whole body.

According to the localisation, type and other characteristics of the cancer, it can be delivered externally by a machine or internally, by implanting the radiation source in the body (the latter is most often done for head and neck, breast, cervix, prostate, and eye cancer).

Radiotherapy can also be used, by itself or in combination with chemotherapy, to shrink large localised tumours before surgery (see Check Up #5, https://fchampalimaud.org/news/check-up-5-what-difference-between-adjuv… ).

Targeted therapy is a more recent type of cancer treatment that uses molecules specially designed to attack the life cycle or function of cancer cells of the patient, with less effects on normal cells. As cancer cells usually have mutations in their DNA that normal cells do not, molecules can be designed that recognise and target the tumoral cells. And since each patient may have different mutations, molecules can be made to target those particular mutations, so this is in fact a form of so-called precision or personalized medicine.

Only a few types of cancer are treated today using only targeted therapy. Some examples of drugs used are imatinib (to treat certain chronic leukemias), erlotinib and vemurafenib (treats certain colorectal, lung, head and neck cancers and melanoma), and certain monoclonal antibodies such as trastuzumab (treats certain breast cancers) and cetuximab (to treat different types of solid tumors). In general, targeted therapy is used in combination with other types of cancer treatments.

Immunotherapy is a cancer treatment that stimulates the patients’ own immune system to attack their cancer. One type of immunotherapy is T-cell transfer therapy, in which immune cells are taken from a patient’s tumor, manipulated in the lab to better attack that tumor, then those are grown in the lab to attain large quantities and injected back into the patient’s bloodstream. 

Monoclonal antibodies created in the lab to mark cancer cells, making them more detectable by the immune system, are another example. Other options are immune system modulators, “immune checkpoint inhibitors” and so-called treatment vaccines, which also boost the immune system’s response. As for immune checkpoint inhibitors, they cancel some of the natural restraints of the immune system, allowing it to more strongly attack cancer cells. This can, however, cause the immune system to attack healthy parts of the body – one of the major serious side effects of immunotherapy. 

Certain melanomas are currently being treated with immunotherapy, but, although its use has been approved for other cancers, it is not yet a first-line cancer treatment.

Source: National Cancer Institute (www.cancer.gov)
By Ana Gerschenfeld, Health & Science Writer of the Champalimaud Foundation.
Reviewed by: Professor António Parreira, Clinical Director of the Champalimaud Clinical Center.
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