Principles of drug treatment in solid tumors
This is asking about the principles of chemotherapy. Chemotherapy is the main treatment for disseminated malignancies and usually requires multiple cycles of IV drugs.
Chemotherapeutics are drugs with selective toxicity against cells in mitosis. They do not act locally, but rather systemically work to prevent cellular replication. As cancer cells replicate at an increased rate, it is logical that such drugs disproportionately affect cancer cells.
The aim of chemotherapy can be curative or palliative depending on the therapeutic scheme, and it can be a single agent or more commonly, multiple agents that have increased synergistic therapeutic effect.
Chemotherapeutics have three mechanisms:
- Damage DNA (e.g. Cisplatin, doxorubicin)
- Inhibit DNA synthesis (e.g. methotrexate)
- Stop mitosis (e.g. vinblastine)
Simply put, chemotherapy can be used in almost any way, by itself,with surgery, radiation therapy or others, pre, or post other treatments or in a palliative form.
Chemotherapy is most effective on tumors that are dividing fast, the more cells in a tumor that are in G1 (rather than G0) the greater the chemotherapeutic effect.
The dose of the drugs is determined by the Phase I trials which look for the maximum tolerated dose. The standar method of determining chemotherapy dosage is based on body surface area, which uses a mathematical formula, including weight and height, to evaluate the dosing levels. If the dose is too high, the drugs will be too toxic, too low, ineffective.