Oncology: Medical Therapies Flashcards
(37 cards)
What is chemotherapy?
Chemotherapy is genotoxic treatment of disease by the use of chemical substances
What are the different applications of chemotherapy?
- Primary- sole- anticancer treatment
- Adjuvant- after surgery ‘mop up’
- Neoadjuvant chemotherapy- beofre surgery to shrink
- Concurrent- with radiation to increase sensitivity of RT
- What cells does chemo target?
- How can cells act as reservoirs?
- What are the targets of chemo?
- Highly proliferating tissues
- Cells in G0 can repopulate
- DNA synthesis, RNA synthesis, protein synthesis, cell cycle progression
When is chemotherapy most and least effective?
What is the major cause of chemotherapy failure?
- Most effective against rapidly dividing cells
- Slow growing (indolent) typically resistant
Drug resistance casues failure
At which stage is chemotherapy most likely to be effective?
C- fast growing, smallest
How are tumours heterogenous?
- Cancer is a result of genetic instability- leads to more varitaion
- As they progress they become ‘subclones’
- Therefore may be lots slightly different
What factors affect chemotherapy success?
- Growth fraction and mass doubling time
- Tumour cell heterogeneity
- Inherent tumour sensitivity
- Drug dosage
- Tumour blood supply/oxygenation
- Interval between treatments
How can drug resistance be minimised?
- Treat as early as possible
- Use standard protocols
- Use correct doses
- Administer agenst properly
- At relapse act ASAP
What tumours should not be pre-treated with steroids?
Lymphoma or mast cells
Causes resistance
What factors influence choice of chemotherapy agents?
- Clinical situation- indication, evidence of benefit
- Owner goals- often palliative, balance between QoL and effect
- Patient- signlamnet, co-morb
- Dosing and schedule
What affects response and side effects of chemotherapy?
- Administration- dose ability to enter blood if oral
- Distribution- target site, cellular uptake (BBB, vasculature)
- Metabolism- drug activation
- Excretion- clearance
What tumour can recieve single agent chemotherapy?
Transmissible venereal tumour
How can polychemotherapy be achieved?
Sequential- several drugs at different times
Combined- several drugs at same time
With polychemotherapy what should they achieve together?
What should be avoided?
Should
* Have proven efficacy
* Different modes of action
* Affect different stages of cell cycle
* non-overlapping dose limiting toxicities
* not interfere
Should avoid
* Arbitrarily exclude one of the drugs from protocol
* Reduce drug dose
What routes of chemotherapy should be avoided?
- Topical
- Intratumoural
When can patients pose dosing problems?
- Obese patients
- Collies with drug sensitivities
- Hepatic function compromise
- Reduced renal function
Why is dosing rate difficult?
High dose chemo has a narrow therapeutic window
Too low- ineffective
Too high- toxic
When should chemotherapy dose be reduced?
Only lower as needed based on actual adverse effects
What is the purpose of dose density?
- Designed to allow recovery of normal tissues
- Rapidly dividing tissue such as bone marrow and GI tract have tremendous capacity to repair rapidly
What is the common first line chemotherapy protocol for a canine lymphoma?
CHOP
* vincristine, doxorubicin, cyclophosphamide, prednisolone
CEOP
* vincristine, epirubicin, cycloposphamide and prednisolone
What is the common first line chemotherapy protocol for lymphoma in cats?
high dose COP
* vincristine, cyclophosphamide and prednisolone
What should be assessed before chemotherapy?
- Tolerance of previous treatment
- Assess patient
- Assess tumour status
- Biochemistry- pre-protocol, every few months
- Haematology prior to treatment
- Urinalysis
What chemotherapy planning needs to take place?
- Risks and benefits with owner
- Ensure- not pregnent, no very young children
- Practice is sufficient to administer drugs safely
- Appropriate PPE is available
- Written owner info
Prior to each chemotherapy treatment what do neutrophils and platlets need to be?
Neutrophils over 3 x 10^9/L
Platelets over 100 x 10^10/L
