Goals Of Chemotherapy
Click the following to see the goals of:
Cell Cycle Specific Chemotherapy Cell Cycle Non-Specific Chemotherapy Combination ChemotherapyCell Cycle Specific Chemotherapy
Given that most cancers have proliferating and resting cells, proliferating cells must be in cycle for phase specific agents to cause their death.
- Because all cells are not in cycle at the same time, cycle specific chemotherapy is administered in divided doses or continuous infusion.
- These methods of administration facilitate the lysis of cells as they enter certain phases of the cycle. These drugs therefore reduce the 'growth fraction' ie the number of cells in cycle.
Cell Cycle Non-Specific Chemotherapy
Non-specific agents cause death independently of the proliferative state of the cell.
They reduce the tumour burden or the number of cells that make up a tumour.
Combination Chemotherapy
Tumours, in their early stages grow rapidly because they have a high growth fraction. As the tumour burden increases its growth plateaus and the growth fraction decreases. Growth fraction and tumour burden are therefore inversely related.
Cycle specific and cycle non-specific drugs are given in combination because:
- Specific drugs reduce a tumour's growth fraction.
- Non-specific drugs reduce the tumour burden.
- The rationale for combining these agents is to achieve maximum tumour cell kill.
Course Of Combination Chemotherapy Treatment
Combination chemotherapy is administered in courses or cycles in order to ensure lysis of proliferating and resting cells.
The drugs used in combination are those that:
- Have demonstrated antitumour activity.
- Have different mechanisms of action.
- Produce synergy.
- Produce similar side effects at different points in time.
- Produce minimal overlapping organ toxicity.
The number of courses used in treatment varies depending on:
- The type of cancer.
- The agents used.
- The patient's response to therapy.
- In theory, a constant percentage of cell kill should occur after each course of therapy, reducing the cancer cell population each time so that, when the last cycle is completed, the body is able to destroy the remaining cancer cells for itself.