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Cancer is a group of diseases which is caused by out of control cell division, which may be due to a defect in a gene, known as mutation. These defective genes can then divide and cause neoplasm of cells leading to a tumour which can essentially invade tissues and spread to other sites of the body (Metastasis). Cancer can be either malignant, where the tumour is able to spread and is thus cancerous, or it can be benign where the tumour does not spread to other parts of the body and is therefore not cancerous. There are various ways in which cancer can be treated some of which include; chemotherapy, radiation, gene therapy, surgery, immunotherapy and hormone therapy. This essay will focus on how the use of antioxidants can either enhance or diminish the effects of chemotherapy.
Chemotherapy treatment aims to interfere with cell division and thus prevent cells from dividing uncontrollably. The treatment involved makes use of various anticancer drugs and/or radiation where anticancer drugs, have different modes of action as they act at different stages of the cell division cycle and can therefore be given in combination. Anticancer drugs act to prevent proliferation of cancer cells by damaging the DNA and proteins via apoptosis. Additionally, the routes of administration of chemotherapy may be intravenous, oral, intra arterial or topical use. The length of the treatment will however, depend upon how well the patient's body responds to the chemotherapy. Alongside cancerous cells, hair follicles and immune cells also divide rapidly and the effects of chemotherapy can hence have adverse effects upon their growth, leading to hair loss, vomiting and other toxic effects. Some of these effects can subsequently be reduced by the use of antioxidants. Cancer Research (online).
Antioxidants are phytochemicals, which are naturally occurring substances that are found in plants and within certain foods. For example, vitamin E (leafy vegetables and nuts), vitamin C (oranges, broccoli and strawberries), selenium (fish, meat and eggs) and β-carotene (carrots) are all antioxidants that can be obtained in the daily diet. American cancer society (online). Antioxidants which are also referred to as 'Free Radical Scavengers' essentially work by delaying the onset of reactive oxygen species (ROS) which are generated by the interaction of radiation with water molecules. When the radiation attacks water, the water molecule loses an electron and becomes an exceedingly reactive hydroxyl radical, this then tries to gain an electron from elsewhere, (such as DNA). Free radicals are consequently unstable molecules which have the ability to cause damage. Lauren Pecorino (2008:239). It is the generation of these free radicals, which can be found in the environment or in the metabolism which occurs in the body that can damage DNA thus leading to uncontrolled mitosis and ultimately cancer. Antioxidants can 'mop up' and neutralize these free radicals, hence reducing its actions of damaging DNA and other cells. National Cancer Institute (online). The use of dietary and supplementary antioxidants alongside endogenous antioxidants can sometimes help maintain a balance in the production of ROS.
Antioxidants in the diet aim to help 'boost' the immune system as they protect the cells from being damaged by free radicals. However, many white blood cells in the body actually make use of the free radicals to enable them to kill viruses. Therefore, the use of antioxidants that 'mops up' these free radicals can prevent the killing of the bacteria, which shows that free radicals can actually be of some benefit and should not be destroyed. In addition to this, the view that antioxidants can benefit the immune system, has led to a large proportion of the population to take antioxidant supplements in an attempt, to further prevent disease and improve overall health. Whereas, the use of high dose antioxidant supplements (exceeding the recommended daily allowance) such as co-enzyme Q10 and green tea extract may conversely have negative effects, as they can reduce the ability of the cells of the immune system to fight an infection. This is because the high doses will stop the generation of any free radicals, which will therefore prevent the leukocytes from being able to remove the viruses and bacteria. In addition to this, the use of antioxidants can interfere with chemotherapy drugs such as alkylating agents that work by generating free radicals in the cancer cells which in turn destroy them. (Goldstein IM, 2000). Consequently, this shows that the use of antioxidants may inhibit the action of the chemotherapy drugs and would thus prevent it from having any therapeutic effect. Similarly, this was supported by Brian D. Lawenda et al. who claimed that antioxidant supplements can further interact with chemotherapy, as they provide the protection of cells and thus prevents the chemotherapy agents from shrinking the tumour. This in turn enables the cancerous cells to still survive. It can thus be seen, that the use of antioxidant supplements in an attempt to reduce the side effects of chemotherapy, may prevent the treatment from working efficiently or completely stop its effects. (Brian D. Lawenda, 2008). In contrast to this, findings from a study carried out by 'The Society of Integrative Oncology' found that there was actually no interference of antioxidants with chemotherapy. In fact, it was found that the use of antioxidants can actually improve the quality of life of the patient, as they reduce the toxic side effects of therapy. For that reason, this can be seen as an advantage, as the antioxidants would enhance patient compliance and ensure that the patient completes the therapy. Cancer Treatment Centers of America (online).
Many researchers have found that when a normal cell moves away from its typical environment, it dies via a sophisticated process known as apoptosis. The death of these cells therefore prevents them from proliferating and growing in other areas. However, it is further suggested that cancerous cells are able to move away from their environment, using an alternative energy source which enabled them to survive with the lack of ATP. The survival of these cells with lack of energy and oxygen production leads them to generate free radicals, which when treated with antioxidants in laboratory environments, astonishingly showed that they actually enable the cancerous cells to survive. (Zachary T. Schafer, 2009). This implies that antioxidants may actually enhance the growth of the cancerous cells as they move away from their environment, hence enabling the spread of the cancer. For that reason, the use of antioxidants can have a reverse effect on the free radicals, because instead of eliminating them, it can actually increase its survival. This in turn may reduce the efficacy of chemotherapy, because the chemotherapy will aim to kill the cancerous cells, whilst the adjunctive use of antioxidants will cause the cancer cells to survive.
Further support is gained from Dr. D' Andrea (Assistant Clinical Member, Department of Medicine, Memorial Sloan-Kettering Cancer Center, NY) who favours that antioxidants should be avoided in chemotherapy. Dr. D' Andrea looked at various research, which showed evidence that cancer patients who were given antioxidants concurrently with chemotherapy showed a decreased survival rate in comparison to those who were not treated with antioxidants. The argument is put forward that there are a higher number of studies which indicate that antioxidants should not be used with chemotherapy, and for that reason patients should be advised not to use them. Many of the research which has been carried out make use of in vitro studies which seem to be unreliable as they are conducted in controlled conditions which may thus affect the validity of the results. (Gabriella M. D'Andrea, 2005). Simone CB (Protective Cancer Institute in Lawrenceville, USA) on the other hand, carried out an in vitro and in vivo study and found that patients who were taking prescribed antioxidants had reduced side effects, protection of the normal tissue and no interference with the chemotherapy. Therefore, this shows that because the antioxidants are able to 'mop up' the highly reactive free radicals it will prevent further damage to the other tissues and has no significant interference with chemotherapy, hence contradicting the findings of Dr.D'Andrea. Pub Med (online).
In conclusion, the concurrent use of antioxidants in the treatment of chemotherapy is a highly controversial topic. However, no definite answer has yet been obtained. I believe that antioxidants should be used whilst undergoing chemotherapy, as they can enhance the immune system which will reduce the patient's body from being susceptible to an infection. In addition to this, it will also reduce the toxic side effects of the treatment which, in turn would ensure that patients are able to cope with the treatment in order for them to continue using it. Furthermore, many of the studies are in vitro; therefore the findings cannot always be applied to humans thus reducing the validity of the results. For that reason, more in vivo studies should be carried out. Overall, more research and clinical trials need to be carried out in order for a more convincing answer.