Question

Explain the significance of growth fraction and the cell cycle to the success of chemotherapy.

Explain the three primary therapies for cancer: surgery, radiation, and chemotherapy.

Answer 1

1. ANS: The growth fraction, the percentage of cancer cells undergoing mitosis at any given time, is the ratio of replicating cells to resting cells. It is a major factor determining the success of chemotherapy. Antineoplastics are more effective against cells that are rapidly
dividing. A high growth fraction means there are many replicating cells. Solid tumors have a low growth fraction; thus, they are less sensitive to chemotherapy. Leukemias and lymphomas have a high growth fraction; thus, chemotherapy is more effective. Hair follicles, bone marrow, and gastrointestinal tissue have a high growth factor; this explains many adverse effects.
The cell cycle proceeds as follows: G0 Phase is the resting stage, G1 Phase is when the cell synthesizes material needed to duplicate DNA, S Phase is when the cell duplicates DNA, G2 Phase is the premitotic phase, M Phase is when mitosis occurs, and then the cell returns to the G0 phase.
To achieve a total cure, every malignant cell must be removed or killed through surgery, radiation, or drugs or by the patient's immune system. Even one cell could reproduce and continue the cancer. The immune system eliminates a very small number of cancer cells,
so it is important to diagnose cancer early and treat with surgery, radiation, and/or drugs (chemotherapy).

2. ANS:

Cancer may be treated using surgery, radiation therapy, and drugs. Chemotherapy may be used for cure, palliation, or prophylaxis.
*Surgery is performed to remove a tumor when it is localized or pressing on nerves, airways, or other vital tissues. Surgery is not an option when tumors affect blood cells or when it would not extend the life span or improve quality of life.
*Radiation and drug therapy are generally more successful.
Radiation can destroy tumor cells. Ionizing radiation is aimed directly at a tumor and may follow surgery. It is used as palliation for inoperable cancers to shrink the size of a tumor and to relieve pain or difficulty in breathing or swallowing.
*Chemotherapy: the use of drugs to treat cancer these are all vesicants. has to go directly into the vessels and not into the tissues because they are toxic to tissues. for dosing you'd give the meds for a certain period of time then take the patient off the drugs to give them time to rest. Works best on cells that are replicating fast.