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Neoplasia

C h a p t e r 7

colon and rectum (rectal examination, fecal occult blood test, and flexible sigmoidoscopy and colonoscopy, Chapter 29), prostate (prostate-specific antigen test- ing and transrectal ultrasonography, Chapter 39), and malignant melanoma (self-examination, Chapter 46). While not as clearly defined, it is recommended that screening for other types of cancers such as cancers of the thyroid, testicles, ovaries, lymph nodes, and oral cav- ity be done at the time of periodic health examinations. Diagnostic Methods The methods used in the diagnosis and staging of can- cer are determined largely by the location and type of cancer suspected. They include blood tests for tumor markers, cytologic studies, tissue biopsy, and gene pro- filing techniques as well as medical imaging, which is discussed with specific cancers later in this text. Tumor Markers Tumor markers are antigens expressed on the surface of tumor cells or substances released from normal cells in response to the presence of tumor. 2 Some substances, such as hormones and enzymes, that are normally pro- duced by the involved tissue become overexpressed as a result of cancer. Tumor markers are used for screen- ing, establishing prognosis, monitoring treatment, and detecting recurrent disease. Table 7-4 identifies some of the more commonly used tumor markers and summa- rizes their source and the cancers associated with them.

Screening, Diagnosis, and Treatment

Advances in the screening, diagnosis, and treatment of cancer have boosted 5-year survival rates to nearly 64%. When treatment cannot cure the disease, it may be used to slow its progression or provide palliative care. Screening Screening represents a secondary prevention measure for the early recognition of cancer in an otherwise asymptomatic population. 50,51 Screening can be achieved through observation (e.g., skin, mouth, external genita- lia), palpation (e.g., breast, thyroid, rectum and anus, prostate, lymph nodes), and laboratory tests and pro- cedures (e.g., Papanicolaou [Pap] smear, colonoscopy, mammography). It requires a test that will specifically detect early cancers or premalignancies, is cost effective, and results in improved therapeutic outcomes. For most cancers, stage at presentation is related to curability, with the highest rates reported when the tumor is small and there is no evidence of metastasis. For some tumors, however, metastasis tends to occur early, even from a small primary tumor. Unfortunately, no reliable screen- ing methods are currently available for many cancers. Cancers for which current screening or early detection has led to improvement in outcomes include cancers of the breast (breast self-examination and mammography, discussed in Chapter 40), cervix (Pap smear, Chapter 40),

Tumor Markers

 TABLE 7-4

Marker

Source

Associated Cancers

Oncofetal Antigens α -Fetoprotein (AFP)

Fetal yolk sac and gastrointestinal structures early in fetal life Embryonic tissues in gut, pancreas, and liver

Primary liver cancers; germ cell cancer of the testis Colorectal cancer and cancers of the pancreas, lung, and stomach

Carcinoembryonic antigen (CEA)

Hormones Human chorionic gonadotropin (hCG)

Hormone normally produced by placenta Gestational trophoblastic tumors; germ cell cancer of testis

Calcitonin

Hormone produced by thyroid parafollicular cells

Thyroid cancer

Catecholamines (epinephrine, norepinephrine) and metabolites Specific Proteins Monoclonal immunoglobulin

Hormones produced by chromaffin cells of the adrenal gland

Pheochromocytoma and related tumors

Abnormal immunoglobulin produced by neoplastic cells Produced by the epithelial cells lining the acini and ducts of the prostate

Multiple myeloma

Prostate-specific antigen (PSA)

Prostate cancer

Mucins and Other Glycoproteins CA-125

Produced by müllerian cells of ovary

Ovarian cancer

CA-19-9

Produced by alimentary tract epithelium Cancer of the pancreas, and colon

Cluster of Differentiation CD antigens

Present on leukocytes

Used to determine the type and level of differentiation of leukocytes involved in different types of leukemia and lymphoma