Chapter 39 Chemotherapy
Chemotherapy is used in treatment of cancer. There are two types of chemotherapy:
The Cell Cycle
To understand how chemotherapy works it is necessary to understand the lifecycle of a cell (Figure 39.1):
• G0 phase (resting stage): the cell is at rest and has not started to divide. This can last for a few hours to a few years, depending on the circumstances (reproductive cells have a very short resting phase whereas plant seeds have been known to germinate many years after they have been deposited). The cell becomes activated.
• G1 phase: the cell starts to make more proteins and is ready to divide. This usually lasts 18–30 hours.
• S phase: the deoxyribonucleic acid (DNA) chains are copied so that the new cell has the same DNA. This usually lasts 18–20 hours.
• G2 phase: this is just before the cell starts splitting into two cells. This phase usually lasts from 2–10 hours.
The Aims of Chemotherapy Treatment
• Control: stopping the disease spreading and try to provide quality of life while the patient is alive.
Terminology
• Adjuvant therapy: postsurgical treatment to prevent the growth of any remaining cells and metastasis around the body.
• Benign tumour: remains confined to original location. There is no invasion of surrounding material or general dispersal. Can be removed by surgery. Generally not life threatening unless in an inoperable place, e.g. certain types of brain tumour.
• Malignant: tumour can invade surrounding material and generally disperse in the body. Often life threatening.
• Metastasis or secondaries: spreads from the main site of the tumour to a distant site, forming new centres of growth.
