Cancer

The American Cancer Society promotes cancer awareness and disseminates information about the disease. Early detection, diagnosis, and treatment of cancer is one of the goals of Healthy People 2010. Due to these initiatives the mortality rates for most major cancers are declining. In fact, 8.4 million Americans - nearly one in 30 - are living with a history of cancer. Additional information about cancer and its treatment can be obtained from the National Cancer Institute.

Neoplasia is a disorder of cell growth and replication. Normal tissue growth stops at a certain point. In neoplasms, tissue growth occurs and persists at the expense of the rest of the body. The cells function and appearance can become abnormal.

Cell Growth and Differentiation

Normally cell growth is determined by certain set information in the genetic code. Cell growth stops when the growth stimulus is no longer present. Normal cell differentiation determines what a cell will look like, how it will function, etc.

Characteristics of Neoplasms.

Neoplasms, however, grow and divide not responding to usual growth and development stimuli. The do not differentiate in the same manner as the surrounding tissue cells. Neoplasms are identified by their, cell characteristics, manner of growth, rate of growth, potential for metastasis, ability to produce generalized effects on the body, ability to cause changes to surrounding normal tissues, and capacity to cause death.

· Cellular Changes: True cancer cells fail to undergo normal cell proliferation and differentiation. The term anaplasia is used to describe the lack of cellular differentiation. They are abnormally arranged and can loose their normal stratified appearance. Cell division and proliferation is increased in part due to alterations in p53, a tumor suppressor gene that is a cell cycle regulator. There is also a decreased response to normal inhibitory factors. Additionally cells demonstrate an enhanced response to hormonal and growth factor stimuli.

· Cell Membrane Changes: Cell surface antigens are coded and developed by the genetic code of a particular cell. May cancer cells produce antigens that are immunologically distinct from the surrounding normal tissue cells. These antigens are recognized as foreign by the body’s immune system, which can contribute to the defense against the neoplasm. Additionally laboratory identification of these antigens is useful in diagnosing a particular type of Cancer. Ex Carcinoembryonic antigen, not normally found in the adult is present in 75% of people with Colon Cancer.

· Metabolic Changes: Cancer cells may utilize different metabolic pathways than normal cells. Changes in these pathways may cause abnormal hormonal secretions. Ex. Some forms of Bronchogenic Ca produce ADH. Additionally cancer cells may produce or secrete substances associated with fetal growth and development that should not be present in normal children or adults. (Onco-feto-proteins.)

Cancer Development

Once the structure and function of the cell has changed, there are other process that lead to the development of neoplastic disease. Cancer cells are able to avoid immune detection and destruction. They are able to alter cellular antigens and antagonize the immune system. Thus these abnormal cells are able persist and continue tumor growth. Continued growth depends upon an adequate blood supply, therefore, neoplasms are able to stimulate the development of their own blood vessels through the process of neovascularization. Loss of normal cellular adhension molecules permits cell migration away from the tumor site. Access to blood vessels and lymphatics provides the means for metastasis to occur.

Paraneoplastic Syndromes

The syndromes are seen in patients with cancer, regardless of the type of cancer. They cannot be explained by the space occupying properties of the tumor. Yet, their presence is so characteristic of the presence of a neoplastic disorder that they can be considered warning signs to search for or rule out the presence of a tumor..

• Constitutional symptoms: Weight loss, anorexia, cachexia, fever. Possibly related to the secretion of tumor necrosis factor, previously called cachetin.

• Hematologic symptoms: anemia and clotting disorders

• Endocrine syndromes: Abnormal secretion of hormones leads to increased ACTH levels and SIADH. Elevated Calcium levels can occur due to secretion of parathryoid hormone related protein resulting in a clinical picture similar to that of hyper parathyroidism.

Carcinogenesis

There appears to be a familial tendency toward certain types of Cancer. This may be due to a genetic predisposition for the development of certain mutations that may lead to cancer.

• An hereditary link to breast cancer is seen in about 5% of all cases of breast cancer. Mutations in the BRCA1 gene are linked to approximately 50% of these cases. A second gene, BRCA2, is linked to an additional 30% of all cases of breast cancer. Thus women in families with these alterations have a greater than 80% risk of developing breast cancer.

• Hormonal factors are also linked to breast cancer development. A late first pregnancy, late menopause, or early menarche, are all associated with an increased risk for developing breast cancer.

• Retroviruses (viruses with RNA and reverse transcriptase that cause their RNA to make a mutant DNA within the cell nucleus) have been demonstrated to cause certain cancers in animals. ie. Feline leukemia

• Additionally there are a wide variety of environmental agents that have been linked to certain cancers, such as cigarette smoke to lung cancer. Additionally radiation can alter the cell structure leading to neoplasm formation.

Treatment

A wide variety of diagnostic methods are used to identify the presence of a tumor. Additionally surgery is used to stage the cancer, and to remove it. Other forms of treatment include radiation and drug therapy.

• Radiation: Radiation is used because it acts at the cellular level, causing cell death by breaking chemical bonds, disrupting DNA, and interfering with cell activity and reproduction. Radiation is of course injurious to all cells, not just the cancer cells. However, normal cells seem to be able to recover from the effects of radiation. Still great care must be taken to see that the radiation is properly focused. The patient goes to several practice sessions, where the location of the tumor is firmly identified. The skin is marked with lines and arrows to indicate where the radiation should be directed. Patients are directed not to remove the marks, and to avoid the use of lotions, creams, or powders on the radiated areas. The radiated area becomes red, hot, and swollen causing discomfort. It can only be washed with cool water. Tight clothing should be avoided. Depending on the location of the radiated area, patients may also have some nausea and vomiting.

• Pharmacotherapeutics: Chemotherapy can be used singly or in combination with other methods. They work by a variety of mechanisms such as interrupting of the production of essential enzymes, inhibiting actions of DNA and RNA, and preventing cell division. They are most effective in treating rapidly growing tumors. However, these same effects are also often visited on normal cells, causing the many side effects that you are familiar with, tinny taste in the mouth, loss of appetite, nausea and vomiting, decreased blood cell counts, and loss of hair. Helping patients and their families cope with all of these side effects as well as with the significance of the diagnosis of cancer can really stretch your nursing skills

• Other: Some tumors respond to various hormones, and the lack of them. Estrogen has been shown to increase size of some breast tumors. Therefore antineoplastic therapy for estrogen receptor positive tumors includes treatment with an anti-estrogen agent, Tamoxifen. Immunotherapy with substances such as interferons is being used to stimulate the body's immune response against the abnormal cells. The newest research is now directed toward blocking the angiogensis (blood vessel) development that occurs in solid tumors. When blood vessel formation is blocked, tumor growth is also blocked.

Concepts in Neoplasia

Diagnosing Breast Cancer

Websites Recommended by Students

http://www.imaginis.com/

Critical Thinking:

What characteristics of neoplastic cells are different from non neoplastic cells, that can be used in the diagnosis and treatment of neoplastic diseases? Answer.

Email responses to: Frizzell@lasalle.edu

Ó JPFrizzell 2003