Pharmville

A group of diseases in which all forms cause cells to change and grow out of control. Most cancers form a lump or mass called a tumor. Tumors can invade and destroy healthy tissue. Tumor cells can break away and travel to other parts of the body. There they can continue to grow. This spreading is called metastasis.

• Neoplastic cells originate from normal body cells
• Transformation of a normal cell into a cancer cell involves mutation of the genes (DNA) of the normal cell
• Early embryonic genes activated at an inappropriate time can cause a cell to develop into a tumor
•  Only one cell has to undergo malignant transformation for cancer to begin
• Benign tumors grow by expansion, whereas malignant tumors grow by invasion
• Most tumors arise from cells that are capable of cell division
• Primary prevention involves avoiding exposure to known causes of cancer
• Secondary prevention of cancer involves screening for early detection
• Tobacco use is a causative or permissive factor in 30% of all malignant neoplasms
• Tumors that metastasize from the primary site into another organ are still designated as tumors of the originating tissue

• Demonstrate rapid or continuous cell division
• Show anaplastic morphology
• Have a large nuclear-cytoplasmic ratio
• Lose some or all differentiated functions
• Adhere loosely together
• Are able to migrate
• Grow by invasion
• Are not contact inhibited

• Ratio of proliferating cells to resting cells.
• Proliferating cells sensitive to chemotherapy because of interrupting DNA synthesis
• Disseminated cancer have high growth fractions whereas solid tumors have low growth fractions

• Chemotherapy drugs are more toxic to tissue with high growth fractions--this includes normal cells
• Bone marrow
• Skin
• Hair follicles
• Sperm
• Gastrointestinal tract

• Toxicity to Normal Cells
• Lack selective toxicity--unable to determine biochemical feature in target cell that normal cells lack
• Cure Requires 100% Cell Kill
• Kinetics of drug-induced cell kill
• Nonparticipation of host defenses in cell kill
• When should treatment stop? When no more visible cancer cells are present.
• Absence of Truly Early Detection
• Metastasis may have occurred
• Tumor will be less responsive to drugs
• Patient may already be debilitated by disease
• Solid Tumors Respond Poorly
• As tumors get larger growth fractions decline 
• Drug Resistance
• Cancer cells develop resistance as course of therapy continues
• Heterogeneity of Tumor Cells
• There is ongoing mutation
• Limited Drug Access to Tumor Cells
• Due to location or blood supply

• Each drug should be effective by itself
• Each drug should have different mechanisms of action
• Drugs should have minimally overlapping toxicities