Principles of chemotherapy Flashcards
Define the following terms:
- Tumour
- Malignant tumour
Tumour:
• Abnormal proliferation of tissue even after the stimuli that evoked the change is gone
Malignant tumour:
• Known as cancer. It implies that the lesion has the ability to invade and destroy adjacent structures
List the treatment options for cancer
- Surgery
- Radiotherapy
- Chemotherapy
- Immunotherapy
- Hormone therapy
Define chemotherapy
- Drugs that are destructive to cells and tissues
- Chemotherapy drugs target cells at different phases of the cell cycle
- Unlike bacteria, cancer cells do not have obvious molecular targets that are foreign to their hosts
- Thus, chemotherapy attacks all cells whether healthy or unhealthy
List the 4 types of chemotherapeutic agents
- Antimetabolites
- Alkylating agents and platinum
- Mitotic spindle poisons
- Anthracyclines
Describe antimetabolites
- Inhibits the use of essential metabolites involved with DNA repair/ DNA nucleotide synthesis
- Thus the cell cannot divide and proliferate
- Antimetabolites can be grouped into folate antagonists and nucleobase/nucleoside analogues
Describe the types of antimetabolites
Methotrexate
• Folic acid is necessary for protein and nucleic acid synthesis. It helps make and repair DNA
• Inhibits the metabolism of folic acid through dihydrofolate reductase
• If folic acid is not metabolised, then DNA cannot be repaired = cell cannot replicate
Nucleobase Analogues
• These drugs target enzymes in DNA replication
• Structurally similar to DNA
• Two types: purine and pyrimidine analogues
Describe the mechanism of action of alkylating agents and platinum
- Works in all phases of the cell cycle
- Forms permanent bonds to nucleotides (guanine) in the DNA strand, and causes cross linkages with other nucleotides
- This just stops the DNA from being able to unwind and replicate
- The cell undergoes cell arrest (as they cannot replicate) and eventually apoptosis
Describe mitotic spindle poisons
- Vinca Alkaloids
- Taxanes
- Cell-cycle specific: attacks cells during division phase only
- Disrupts the mitotic spindles in cells = impaired mitosis. In health, mitotic spindles separate chromosomes into the two daughter cells
- They bind to tubulin (protein that makes spindle fibres) and cause inhibition of mitosis
- Two types: Vinca Alkaloids and Taxanes
Vinca Alkaloids
• Binds to tubulin and prevents assembly of microtubules
• Prevents “polarisation”
Taxanes
• Binds to tubulin, stabilizes it and prevents disassembly of microtubules
• Prevents “depolarisation”
Describe the mechanism of action of anthracycline
• Anthracyclines damage the DNA in cancer cells
They work in 4 ways:
• Inserting themselves into DNA base pairs (ruining the DNA structure)
• Cause free radical damage to DNA ribose
• Inhibit topoisomerase II enzyme, which would otherwise help cut through tangled DNA strands
• Interact with histones, causing histone eviction and loss of the chromosome structure
List the common chemotherapy side-effects
- Nausea
- Fatigue
- Hair loss/alopecia
- Diarrhoea
- Infection (White cells)
- Bleeding/bruising (Platelets)
- Anaemia (RBC)
Name the drug responsible for these side effects:
• Acoustic damage
• Nephrotoxic damage
• Haemorrhagic cystitis
Alkylating agents and platinum
Name the drug responsible for this side effect:
• Peripheral neuropathy
Mitotic spindle poisons
Name the drug responsible for these side effects:
• Cardiotoxicity
• Pulmonary fibrosis
Anthracyclines
Identify common dental side effects of chemotherapy
- Dry mouth
- Dysgeusia
- Mucositis
- Infection
Explain dental care prior to chemotherapy
- Complete invasive procedures prior to chemotherapy
- Postpone elective oral surgical procedures until cancer treatment is completed.
- Identify and treat carious and mucosal lesions, as well as perio and endo disease
- Identify and eliminate sources of oral trauma and irritation such as ill-fitting dentures, orthodontic bands, and other appliances.
