Chapter 6Cancer

Frequency and Significance

• Cancer is the 2nd leading cause of death in the United States

• Obviously, the term cancer covers many types of malignant neoplasms

• The treatment and outcome for these various neoplasms is widely different

Frequency and Significance

• The prognosis of cancer depends on several items:– The type of cancer– The extent of spread at the time of

discovery– The efficacy of existing therapy

• The incidence of malignant tumors is twice the mortality rate.

Common Cancers

• The most common cancers are basal and squamous skin cell carcinomas of the skin.– These account for 99% of all skin cancers– However, they are rarely fatal

• Malignant melanoma accounts for 1% of skin cancers, but is fatal in about 20% of patients!– This discusses the “type” variable of

prognosis

Common Cancers

• The “treatment” variable of prognosis is readily evident when discussing colon and lung cancer

• Colon cancer is cured in 50% of patients by surgical removal

• Lung cancer treatment on the other hand, is relatively ineffective—a 13% 5 year survival rate

Etiology

• Cells must undergo an alteration called initiation to acquire autonomous growth potential

• Initiation is stimulated by carcinogens which may be physical, chemical or biologic agents

Etiology

• Promotion is the step after initiation, and is the selective growth of the initiated cells

• Progression follows, and is the acquisition of additional DNA mutations

Oncogenes

• Initiators turn oncogenes “on”, which leads to the proliferation of the cell through growth enhancing products

• Oncogenes are supposed to be kept in check by tumor suppressor genes; however, there can be mutations in the tumor suppressor genes that prevent them from functioning properly

Prevention and Cure of Cancer

• While a grand idea, it is an extremely complex task that depends on the discovery of:– Oncogenes – Tumor suppressor genes– Other target genes– Initiating agents

Local and Systemic Manifestations

• Unfortunately, many cancers are asymptomatic until very late in their course– This can affect treatment options

• Local manifestations relate to symptoms at the cancer site—pain for example.

Local and Systemic Manifestations

• Systemic manifestations relate to symptoms not limited to the cancer site—anemia for example.

Diagnosis

• Diagnosis can be made by a variety of tests– Biopsy– Blood smear– Cytology– Radiologic Examination– Endoscopic Examination

TNM System

• T—tumor, the size and invasion into surrounding tissue

• N—extent of lymph node metastasis

• M—whether distant metastasis has occurred

• Stage I is localized, Stage IV is metastasis

Treatment

• Surgical Removal

• Radiation Therapy

• Chemotherapy