Cancer and Chemotherapy in Veterinary Medicine

Question 1

What are the main differences between veterinary and human chemotherapy?

Answer 1

• Same drugs but smaller doses
• Less intense schedule
• Palliation/ Control rather than a cure
• Aim is to prolong life

Question 1

What is the definition of chemotherapy?

Answer 1

The treatment of disease by the use of chemical substances, especially the treatment of cancer by cytotoxic and other drugs

Question 2

How do cytotoxic drugs work?

Answer 2

Cytotoxic drugs interfere with cell growth or division
some act at specific stages of the cell cycle
some are cell cycle non-specific

Question 3

Where do cytotoxic drugs work best?

Answer 3

• They work best on actively divding cells
• Tumours with a high mitotic index are more likely to be sensitve

Question 4

What kind of cells does chemotherapy target?

Answer 4

Rapidly dividing cells

Question 5

When is the best time for cancer treatment?

Answer 5

• Treat as early as possible in the disease course
• Following surgery
• Start treatment as soon as the surgical wound has healed

Question 6

What is neoadjuvant chemotherapy?

Answer 6

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

Question 7

How do you dose cytotoxic drugs?

Answer 7

• Use at the maximum tolerated dose -> highest fractional kill with each treatment
• Multiple doses are usually required
• Pulse dosing at intervals

Question 8

What is combination chemotherapy?

Answer 8

More likely to be effective than a single agent (less selection pressure)

Question 9

What drugs should you use for combination chemotherapy?

Answer 9

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

Question 10

What is the induction stage of chemotherapy?

Answer 10

• Initial treatment protocol, fairly intense
• Aim to induce remission (i.e. state where tumour is not clinically
  detectable)

Question 11

What is the maintenance stage of chemotherapy?

Answer 11

• Follows induction, less intense
• Aim to maintain remission

Question 12

What is the re-induction stage of chemotherapy?

Answer 12

• When tumour relapses
• Return to initial protocol - Aim to re-induce remission

Question 13

What is the rescue stage of chemotherapy?

Answer 13

• When tumour becomes resistant to current therapy
• Use different drugs that tumour has not been exposed to before with different mechanism of action

Question 14

What factors affect the success of chemotherapy?

Answer 14

• Tumour Cell Type
• Drug distribution
  Development of resistance

Question 15

How do we best choose a chemotherapeutic protocol?

Answer 15

• Look at the disease
• Look at the patient
• Look at the owner

Question 16

What is adjuvant chemotherapy

Answer 16

• Delays/ eliminates microscopic metastasis
• Delays/ avoids recurrence after incomplete surgical margins

Question 17

What is neoadjuvant chemotherapy?

Answer 17

Volume reduction that allows surgical resection

Question 18

What are the routes of chemotherapy administration?

Answer 18

• Oral
• IV
• SC
• Intra-Cavitary
• Intra-lesional
• IA

Question 19

How do you handle oral chemotherapy drugs?

Answer 19

• Use gloves
• Dont cut or crush
• Child-Proof container
• Owner handling advice

Question 20

How would IV chemotherapy be administered?

Answer 20

• IV exclusive administration drugs
• Minimise trauma in the peripheral veins
• Stressed or aggressive patients should be sedated

Question 21

What is intra-arterial chemotherapy?

Answer 21

Standard chemotherapy is delivered via a peripheral vein
Cytotoxic agent circulates via heart and lungs before reaching
the arterial supply of the tumour

Question 22

What is the indication of Intracavitary chemotherapy?

Answer 22

– Malignant effusions
– Mesotheliomas, carcinomatosis

Question 23

What drugs are used for intracavitary chemotherapy?

Answer 23

5-Fluoruracil, carboplatin, mitoxantrone

Question 24

What may cytotoxic drugs cause?

Answer 24

They may cause tissue damage

Question 25

When may Diarrhoea occur?

Answer 25

3-5 days post administration
Colitis with doxo- due to straining
Methotrexate- after long Tx period

Question 26

What other reasons can cause diarrhoea?

Answer 26

• Diet changes
• Parasites/ Bacteria

Question 27

What is ileus paralyticus?

Answer 27

• Caused by vincristine
• Causes inappetence in cats, constipation and abdominal pain

Question 28

What is the plan for fixing ileus paralyticus?

Answer 28

• Dose change
• Discontinuation
• Vinblastine

Question 29

What is the plan for fixing nausea and vomiting?

Answer 29

• Prophylactic administration of anti-emetic drugs
• Prophylaxis post administration
• Management and preventative plan

Question 30

What causes cardiotoxicity?

Answer 30

Doxorubicin
* Cardiac myocytes are more sensitive to free radical damage
* Decreases contractability
* Toxicity is dependent of the concentration peak in blood

Question 31

What causes urinary system toxicity?

Answer 31

• Sterile cystitis
• 10% cyclophosphamide

Question 32

What is the prognosis of sterile cystitis?

Answer 32

Irreversible if marked fibrosis occurs
Can rule out urinary tract infection

Question 33

What is lomustine?

Answer 33

• Has a 7% Liver Failure Prevalence in dogs
• Approx 50% have high ALT
• Unpredictable

Question 34

What does asparaginase cause?

Answer 34

• Skin reaction
• Can be prevented using antihistamines

Question 35

What does doxorubicin cause?

Answer 35

Mast cell degranulation

Question 36

What does Cisplatin cause in cats?

Answer 36

Fatal Pulmonary edema