Approaches for the Treatment of Cancer

Added on - 16 Sep 2019

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APPROACHES FOR THE TREATMENT OF CANCER1.0.IntroductionCancer (malignant tumors or neoplasm) is a generic term for a large group of diseases that canaffect any part of the body. One defining feature of cancer is the rapid creation of abnormal cellsthat grow beyond their usual boundaries, and which can then invade adjoining parts of the bodyand spread to other organs, the latter process is referred to as metastasizing. Metastases are themajor cause of death from cancer (The point, 2015). It is considered as a major public healthproblem worldwide and is the second leading cause of death in the United States; leading causeof death worldwide, accounting for 8.2 million deaths in 2012 (Cancer, 2015). The mostcommon causes of cancer death are cancers of lung (1.59 million deaths), liver (745 000 deaths),stomach (723 000 deaths), colorectal (694 000 deaths), breast (521 000 deaths) and esophagealcancer (400 000 deaths) (Cancer, 2015). The values reflect the intensity of the disease on thesurvival of life of victims and gave an insight to apply an adequate treatment. Therefore, thefocus has been given to review the available modalities of treatment. The present paper describesthe pathophysiology, available treatment modalities along with novel methods and possibilitiesto explore for newer modes of treatment.2.0. Search strategyThe available and popular sources were used to search for the evidences. The sources, diverseonline electronic resources including BNI (British Nursing Index), CINAHL (Cumulative Indexto Nursing and Allied Health Literature), EMBASE (the Excerpta Medica database), Pubmed,The DARE (Database of Abstracts of Reviews of Effects), HTA (Health Technology AssessmentDatabase) and NHS (Economic Evaluation Database). In addition, the available text books,magazines and articles from news papers from library have been searched to find out the relevantliterature on the modalities for the treatment of cancer. The search was made for past 30 years tocollect the relevant sources and link the evidences to the current context. Adequate measureswere made to channel the quest for the pertinent sources. The keywords utilized for the pursuitincorporate ‘pathophysiology of cancer, treatment of cancer, novel methods for prevention ofcancer, etc. The outcome of the search for the relevant sources has been depicted in subsequentsections.1
3.0.Cancer PathologyIn the cell cycle, dividing cells undergo one mitosis (M) after another, passing through G1,S(DNA synthesis phase), and G2 phases. Some cells leave the cycle temporarily, entering a G0state from which they can be rescued by appropriate mitogenic stimuli. Other cells leave thecycle permanently, entering terminal differentiation.Any population of cells can grow in number by any one of three mechanisms including (i)shortening the length of the cell cycle, (ii) decreasing the rate of cell death and (iii) moving G0cells into the cell cycle. All three mechanisms operate in normal and abnormal growth. In mosttumors, all three mechanisms are important in determining the growth of the tumor, which is bestcharacterized by its doubling time. Doubling time of tumors range from as little as 17 days forEwing sarcoma to more than 600 days for certain adenocarcinomas of the colon and rectum.However, the fastest growing tumor is probably Burkitt’s lymphoma, with a mean doubling timeof less than 3 days.Cancer is a multi-step process in which multiple genetic alterations must occur, usually over aspan of years, to have a cumulative effect on the control of cell differentiation, cell division andgrowth. Among human tumors, heritable mutations are an exception. Most alterations areacquired in somatic life in the form of chromosomal translocations, deletions, inversions,amplifications or point mutations. Certain oncogenic viruses play important roles in a few humantumors E.g., human papilloma-virus in cervical cancer and skin tumors.The application of molecular biological techniques in the field of tumor virology, cytogenetic,and cell biology led to the discovery of the transforming genes of tumor viruses, the genesactivated at the breakpoints of non-random chromosomal translocations of lymphomas andleukemia (Carlos and Harlan, 1994). Oncogene products are positive effectors of transformation.They impose their activity on the cell to elicit the transformed phenotype and can be consideredpositive regulators of growth. To the transformed cell, they represent a gain in function. Tumorsuppressor gene products are negative growth regulators and their loss of function results inexpression of the transformed phenotype.The normally functioning cellular counterparts of the oncogenes, called proto-oncogene are alsoimportant regulators of biological processes. They are localized in different cell compartments,2
are expressed at different stages of the cell cycle, and appear to be involved in the cascade ofevents that maintain the ordered procession through the cell cycle.In addition, the cell cycle is regulated by external mitogens (e.g. growth factors, peptide andsteroid hormones, lymphokines), which activate a process called signal transduction by whichspecific signals are transmitted within the cell to the nucleus. The process is also mediated bynon integral membrane associated proteins belonging to the tyrosine kinase, RAS gene families,and members of the MAPK family. Signals generated by mitogenic stimulation can lead to theexpression of specific genes coding for proteins localized in the nucleus. Certain members of thenuclear oncogene protein family have been shown to be transactivators of specific RNAtranscripts.4.0.Types of treatment in practiceThe common methods in practice for the treatment of cancer include surgery, chemotherapy, andradiation therapy. Surgery is often the first treatment option if the tumor can be taken out of thebody. Sometimes only part of the tumor can be removed. Radiation, chemotherapy, or bothmight be used to shrink the tumor before or after surgery. Surgery also plays a key role indiagnosing cancer and finding out how far it may have spread. The details are discussed insubsequent sections4.1.SurgerySurgery is used to prevent, diagnose, stage, and treat cancer. Surgery can also relieve (palliate)discomfort or problems related to cancer. Sometimes, one surgery can take care of more than oneof these goals. In other cases, different operations may be needed over time. Surgery can beexplored to estimate the intensity of cancer. In most cases, the only way to know if a person hascancer and what kind of cancer it is by collecting a small piece of tissue and testing it. Thediagnosis is made by looking at cells from the sample with a microscope or by doing other labtests on it. The entire procedure is referred as biopsy. Another mode of surgery (staging surgery)is done to find out how much cancer there is and how far it has spread (Rungruang andAlexander, 2012). During this surgery, the area around the cancer including lymph nodes andnearby organs is examined. This is important because it provides information to guide treatmentdecisions and predict how people will respond to treatment. The curative or primary surgery is3
usually done when cancer is found in only one part of the body, and it’s likely that all of thecancer can be removed. In this case, surgery can be the main treatment. It may be used alone oralong with other treatments like chemotherapy or radiation therapy, which can be given before orafter the operation. Another type of surgery, debulking surgery is used to remove some, but notall, of the cancer for instance ovarian cancer (Schorge et al., 2010). It’s sometimes done whentaking out the entire tumor would cause too much damage to nearby organs or tissues. Forexample, it may be used for advanced cancer of the ovary and some lymphomas. In these cases,the doctor may take out as much of the tumor as possible and then treat what’s left withradiation, chemotherapy, or other treatments. Palliative surgery is used to treat problems causedby advanced cancer (Gray and Adnan, 1997); correct a problem that’s causing discomfort ordisability. For example, some cancers in the belly (abdomen) may grow large enough to blockoff (obstruct) the intestine. If this happens, surgery can be used to remove the blockage.Palliative surgery may also be used to treat pain when the pain is hard to control by other means(Hosoya and Lefor, 2011). Palliative surgery helps ease problems caused by cancer and helpspeople feel better, but it’s not done to treat or cure the cancer itself. Supportive surgery is done tohelp make it easier for people to get other types of treatment. For example, a vascular accessdevice such as a Port-A-Cath® or Infusaport® is a thin, flexible tube that can be surgicallyplaced into a large vein and connected to a small drum-like device that’s placed just under theskin. A needle is put into the drum of the port to give treatments and draw blood, instead ofputting needles in the hands and arms each time.Reconstructive surgery is used to improve the way a person looks after major cancer surgery. It’salso used to restore the function of an organ or body part after surgery. Examples include breastreconstruction after mastectomy or the use of tissue flaps, bone grafts, or prosthetic (metal orplastic) materials after surgery for head and neck cancers. Preventive or prophylactic surgery isdone to remove body tissue that’s likely to become cancer-even though there are no signs ofcancer at the time of the surgery. Sometimes an entire organ is removed when a person has acondition that puts them at very high risk for having cancer there. The surgery is done to reducecancer risk and helps prevent the chance of cancer, but it doesn’t guarantee cancer prevention.For example, some women with a strong family history of breast cancer have an inherited changein a breast cancer gene (called BRCA1 or BRCA2). Because the risk of breast cancer is very4
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