Cancer and Chemotherapy in Veterinary Medicine Flashcards
What are the main differences between veterinary and human chemotherapy?
- Same drugs but smaller doses
- Less intense schedule
- Palliation/ Control rather than a cure
- Aim is to prolong life
What is the definition of chemotherapy?
The treatment of disease by the use of chemical substances, especially the treatment of cancer by cytotoxic and other drugs
How do cytotoxic drugs work?
Cytotoxic drugs interfere with cell growth or division
some act at specific stages of the cell cycle
some are cell cycle non-specific
Where do cytotoxic drugs work best?
- They work best on actively divding cells
- Tumours with a high mitotic index are more likely to be sensitve
What kind of cells does chemotherapy target?
Rapidly dividing cells
When is the best time for cancer treatment?
- Treat as early as possible in the disease course
- Following surgery
- Start treatment as soon as the surgical wound has healed
What is neoadjuvant chemotherapy?
Conversion of tumour pseudocapsule into a thick,
collagenised capsule with no viable tumour cells
(documented in people)
* creates a better defined tumour which is more amenable to complete histiologic excision
How do you dose cytotoxic drugs?
- Use at the maximum tolerated dose -> highest fractional kill with each treatment
- Multiple doses are usually required
- Pulse dosing at intervals
What is combination chemotherapy?
More likely to be effective than a single agent (less selection pressure)
What drugs should you use for combination chemotherapy?
Are known to be effective as single
agent
Have different modes of action and don’t
interfere with each other
Act at different stages of the cell cycle
Don’t have overlapping toxicities
What is the induction stage of chemotherapy?
- Initial treatment protocol, fairly intense
- Aim to induce remission (i.e. state where tumour is not clinically
detectable)
What is the maintenance stage of chemotherapy?
- Follows induction, less intense
- Aim to maintain remission
What is the re-induction stage of chemotherapy?
- When tumour relapses
- Return to initial protocol - Aim to re-induce remission
What is the rescue stage of chemotherapy?
- When tumour becomes resistant to current therapy
- Use different drugs that tumour has not been exposed to before with different mechanism of action
What factors affect the success of chemotherapy?
- Tumour Cell Type
- Drug distribution
Development of resistance
How do we best choose a chemotherapeutic protocol?
- Look at the disease
- Look at the patient
- Look at the owner
What is adjuvant chemotherapy
- Delays/ eliminates microscopic metastasis
- Delays/ avoids recurrence after incomplete surgical margins
What is neoadjuvant chemotherapy?
Volume reduction that allows surgical resection
What are the routes of chemotherapy administration?
- Oral
- IV
- SC
- Intra-Cavitary
- Intra-lesional
- IA
How do you handle oral chemotherapy drugs?
- Use gloves
- Dont cut or crush
- Child-Proof container
- Owner handling advice
How would IV chemotherapy be administered?
- IV exclusive administration drugs
- Minimise trauma in the peripheral veins
- Stressed or aggressive patients should be sedated
What is intra-arterial chemotherapy?
Standard chemotherapy is delivered via a peripheral vein
Cytotoxic agent circulates via heart and lungs before reaching
the arterial supply of the tumour
What is the indication of Intracavitary chemotherapy?
– Malignant effusions
– Mesotheliomas, carcinomatosis
What drugs are used for intracavitary chemotherapy?
5-Fluoruracil, carboplatin, mitoxantrone
