Radiotherapy and antioxidants

• Antioxidants and radiotharepy
• Antioxidants' uses
• Antioxidants' types

Radio therapy or radiation therapy is used in the treatment of cancers. The types of cancer treatment include surgery, chemotherapy and radiation therapy. Surgery helps in separating the tumor from the body. Chemotherapy aims to kill the tumor cells which are detached from the tumor and spread to different parts of the body before they get lodged in some parts and grow into another tumor. Radiotherapy treatment for cancer dates back to the discovery of X-rays by Roentgen in 1985. The purpose of giving radio therapy in addition to surgery and chemotherapy is to prevent the tumor from growing again locally. It is also used to shrink the tumors and kill cancer cells which cannot be operated or for palliation i.e, to reduce pain and discomfort for the patients.

Cancer radiotherapy can be given in many ways

1. EBRT – External beam radiation therapy: EBRT uses a linear accelerator which accelerates the electrons in a machine and is allowed to hit a target. Photon energy is produced during this process which is directed towards the tumor in patient’s body.

2. Brachy therapy: Brachytherapy uses radiation from radioactive materials which is placed in or near the cancer cells as seeds, ribbon or wires

3. Interstitial radiation therapy: In interstitial brachytherapy, a radioactive source is placed within the tumor tissue such as within a breast cancer or a prostate cancer.

4. Intra cavitary radiation therapy: In intracavitary radiation therapy, a radioactive source is placed within a body cavity such as chest.

Radiotherapy acts by breaking the DNA strands in the nucleus of cells. Radiotherapy acts by two different methods. It acts directly by causing DNA strand breakage. Indirectly, it activates the water molecules in the cells to produce free radicals. These free radicals can cause injury to the cells by destructing the DNA.

Free radicals are atoms or group of atoms with unpaired electrons. Free radicals are formed when oxygen interacts with certain molecules during metabolism. Free radicals can destroy the cellular DNA or the cellular membrane leading to impaired functioning or death of the cell. Free radicals are highly reactive and can start a chain reaction causing damage to the cells and tissues.

Antioxidant system is an endogenous system maintained by the body to reduce the effect of free radicals or reactive oxygen species.

There are two different types of antioxidant systems inside the body; enzymatic and non-enzymatic. Enzymatic antioxidants include superoxide dismutase which catalyses the conversion of superoxide anions to hydrogen peroxide, catalase which converts hydrogen peroxide to water and oxygen and glutathione peroxidase which converts hydrogen peroxide to water.

Non enzymatic systems of antioxidants include vitamin E, vitamin A, vitamin C and glutathione. Glutathione helps in reducing the concentration of reactive oxygen species. Glutathione is a tri-peptide, L-γ-glutamyl-L-cysteinylglycine. A tri-peptideis a peptide consisting of three aminoacids joined by peptide bonds. Glutathione has a sulfhydryl group and is able to donate a hydrogen ion and unpaired electron to neutralise the free radicals.

Antioxidants in general can be called as free radical scavengers. Free radicals are found to be responsible for many diseases like cancer and diabetes and plays a role in aging etc.

Antioxidants help in reducing the incidence of these lifestyle related illnesses and reduce the pace of aging.

Antioxidants and cancer is a topic gaining importance these days. Many studies have come out with the result that low levels of antioxidants in the body and the occurrence of different types of cancer are related. Role of antioxidant in the treatment of cancer is also under discussion.

Radio therapy or radiation therapy is the regional form of treatment for the control of cancers. Radiation therapy produces free radicals by ionization. The resulting free radicals produce DNA strand breaks in the nucleus of cancer cells. The effectiveness of radiotherapy depends upon the level of antioxidants like glutathione in the cells. Elevated levels of glutathione will make the cell more radio resistant. In other words if the level of glutathione is very high in the cells, then the free radicals generated from irradiation will be neutralised by glutathione and the cell will not be damaged.

While destroying the tumor cells, radiation therapy can also cause injury to the normal tissues. The extent of damage caused to the normal tissue increases with the size of the tumor.

This is still a topic which has not reached consensus. Some literature argue that it is beneficial to supplement antioxidants during radiotherapy to reduce the side effects while some are of the opinion that antioxidant supplement during radiotherapy should be avoided as it can hamper the effect of treatment.