Chemotherapy

Question 1

what are the 3 main sites of action of cytotoxic agents used in chemotherapy
give 3 examples

Answer 1

Alkylating agents (platinum compounds e.g. cisplastin)

Anti-metabolites (e.g. 5-fluorouracil, methotrexate)

Spindle poisons (e.g. Vinca alkaloids, Taxoids)

Question 2

Alkylating agents (Platinum compounds):
mechanism of action

Answer 2

allow covalent bond to form between DNA strands

replication cant occur - tumour cant grow further

Question 3

Anti-metabolites:

mechanism of action of 2 main agents

Answer 3

5-fluorouracil:
activated to 5-FdUMP: inhibits action of thymidylate synthase, preventing pyrimidines to be incorporated into DNA

methotrexate:
inhibit dihydrofolate reductase (necessary to form purines and thymine pyrimidine): unable to form DNA

Question 4

Spindle poisons:

mechanism of action of 2 main agents

Answer 4

Vinca alkaloids and Taxoids: inhibit tubulin
Taxoids: promote and stabilise tubulin (preventing it being broken down)

= damage to spindle fibre and cell death

Question 5

3 mechanisms that cells can cause cells to become resistant to chemo

Answer 5

decreased entry / increased exit of agent

inactivation of agent in cell

enhanced repair of DNA lesions produced by alkylation

Question 6

what are the main adverse effects of chemo treatment

Answer 6

based on cytotoxic effects affecting rapidly dividing cells:
hair, GI mucosa

haematological toxicity: mainly affects neutrophils, platelets
(risk sepsis)

Question 7

how is response of cancer to chemo monitored

Answer 7

radiological imaging
tumour marker blood tests
bone marrow testing

Question 8

what is the overall effect of chemotherapy drugs

Answer 8

limit proliferation of malignant cells (actively dividing cells not in G0)