Involve. Supporting you. Supporting your patients with cancer
At this moment, 24.6 million people worldwide are living with cancer. The National Cancer Institute estimates that there will be 1,479,350 new cases of cancer in 2009 in the US alone. As the incidence of cancer has increased, the role of the oncology nurse has expanded and cancer treatment innovation has advanced to meet the needs of patients. The following pages provide background information about cancer and cancer care to help oncology nurses stay abreast of the evolving oncology landscape so that they can provide the highest-quality patient care.
Defining Cancer: A Brief Overview
While the exact cause of cancer remains unknown in most instances, multiple theories of carcinogenesis, the underlying etiologic pathway that leads to cancer, have been put forth. The 2 most accepted models of carcinogens are:
- Vogelstein and Kinzler – Emphasizes that cancer is ultimately a disease of damaged DNA, comprised of a sequence of genetic mutations that can transform normal cells to cancerous cells. The genetic mutations involved include inactivation of tumor suppressor genes and activation of oncogenes. Compared with cancers arising in the general population, individuals with a major inherited predisposition to cancer are born with inherited (ie, germ line) mutations in genes involved in cancer causation, giving them a head start on the pathway to cancer. Similar mutations would be expected to result in cancer progression among all individuals; however, in those without a major inherited cancer predisposition, the mutation would occur as a somatic mutation later during their lifetime.
- Hanahan and Weinberg – Focuses on the hallmark events at the cellular level that lead to a malignant tumor. In this model, the hallmarks of cancer include sustained angiogenesis, limitless replicative potential, evading apoptosis, self-sufficiency in growth signals, and insensitivity to antigrowth signals, leading to the defining characteristics of malignant tumors by giving them the ability to invade and metastasize. This model highlights the fact that malignant tumors arise and flourish within the environment of a whole organism. The tissue organizational field theory posits that carcinogenesis is better conceptualized at the level of tissues rather than cells. This theory is based on the dual premise that carcinogenesis is driven by defects in tissue organization and that all cells are inherently in a proliferative state.
Risk Factors Associated With the Development of Cancer
Many epidemiologic studies have demonstrated the association between modifiable lifestyle factors or environmental exposures and specific cancers. Understanding these risk factors and discussing them with your patients may be the first step in cancer care and prevention:
- Cigarette smoking/tobacco use – A strong association has been established between use of tobacco and the development of cancer in multiple sites throughout the body.
- Infections – an estimated 18% of cancers globally are believed to be related to infection, with a higher percentage noted in developing nations (26%) than in developed nations (8%). Examples include human papillomavirus (HPV) and cervical cancer, hepatitis B and C viruses and liver cancer, Epstein-Barr virus and Burkitt's lymphoma, and Helicobacter pylori and gastric cancer.
- Radiation – Exposure to radiation, particularly ultraviolet radiation and ionizing radiation, is directly related to the development of cancer. Exposure to solar ultraviolet radiation is the primary cause of nonmelanoma skin cancers, the most common malignancies in human populations.
- Diet – While the association between diet and the development of cancer is still considered uncertain, several studies have demonstrated the protective effect of diets high in fruits and non-starchy vegetables and low in fat.
- Alcohol – The dietary factor with the strongest established link to the development of cancer. Alcohol consumption is believed to increase the risk of cancers of the mouth, esophagus, breast, and colorectum.
- Physical activity – Epidemiologic evidence suggests that people with physically active lifestyles have a lower risk of certain malignancies than their more sedentary counterparts.
- Obesity – Identified as a risk factor for the development of postmenopausal breast cancer and cancers of the esophagus, pancreas, colorectum, endometrium, and kidney.
Staging Cancer
Once a malignancy is diagnosed, the cancer is staged. Cancer staging is the process of determining the status of the cancer so that appropriate treatment can be identified. Most cancers are staged based on the following:
- The size of the tumor
- Whether the cancer has spread
- If the cancer has spread, how far it has spread
A variety of systems are used to determine cancer staging, but one of the most common is the TNM staging system.
The TNM Staging Guide Explained
The TNM staging guide assigns cancer types a "T" category, an "N" category, and an "M" category. The letters in TNM staging represent the following:
| TNM Staging Guide | |
|---|---|
| T = Tumor | |
| TX: | Tumor cannot be evaluated |
| T0: | No evidence of an original tumor |
| Tis: | Cancer is "in situ" or has not spread |
| T1-T4: | Describe tumor size and status of spreading |
| N = Nodes | |
| NX: | Nearby lymph nodes cannot be evaluated |
| N0: | The cancer has not spread to lymph nodes |
| N1-N3: | Status of cancer spreading into lymph nodes |
| M = Metastasis | |
| MX: | Distant spread cannot be evaluated |
| M0: | No evidence of distant spreading |
| M1: | Distant spreading has been found |
After the TNM stage of the cancer is determined, an overall cancer stage of 0, I, II, III, or IV is assigned. The higher the overall cancer stage, the more advanced the cancer is.
| Stage | Definition |
|---|---|
| Stage 0 | Carcinoma in situ (early cancer that is present only in the layer of cells in which it began) |
| Stage I Stage II Stage III |
Higher numbers indicate more extensive disease: greater tumor size, and/or spread of cancer to nearby lymph nodes and/or organs adjacent to the primary tumor |
| Stage IV | The cancer has spread to another organ |
Interested in learning more about cancer? Visit CancerInformation.com for in-depth oncology information.
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