Oncology Treatment Flashcards
Two different ‘goals’ of therapy
- definitive intent (curative intent)
2. palliative intent-alleviation of clinical signs & symptoms without necessarily aiming to prolong survival
5 factors affecting choice of therapy
- client expectations (def. vs. palliative)
- age of animal
- finances
- risk aversion & aggressiveness
- treatments available (e.g. Sx, radiation therapy, chemotherapy)
Why is excisional biopsy controversial in oncologic surgery?
diagnostic, but chance to cure diminished
What is a preferable way to excisional biopsy of planning a definitive surgical procedure?
FNA/cytology or needle core biopsy/histopathology
When is the best chance to cure with oncologic surgery?
FIRST surgical procedure
Define a “margin”
the cuff of grossly normal tissue removed with the tumor
Are skin and fat (aka the components of lateral margins) good barriers to tumor growth?
no
Which margins are good barriers to tumor growth?
deep margins (things like fascia, bone)
What is the MOST common mistake in oncological surgery?
using too low of a surgical dose
What types of surgery are recommended for most solid tumors?
radical or wide excision
Four treatment options if margins are incomplete
- no treatment; monitor
- wide resection of surgical wound
- postop radiation therapy
- staging resection of surgical wound (*rare in vetmed)
Partial Response (PR)
at least 30% shrinkage of a tumor in at least one dimension
Progressive Disease (PD)
at least 20% enlargement in at least one dimension
___ % of dogs with canine appendicular osteosarcoma have micrometastases
90%
Ten Rules of Surgical Oncology
- a chance to cut is a chance to cure
- the OR is not the place to plan surgery
- if it’s worth taking out, it’s worth turning in
- change gloves and instruments for closure
- minimal tumor manipulation
- avoid multifilament suture
- avoid electrocautery or laser at margins
- beware of pseudocapsules
- no drains or flaps
- don’t compromise surgical dose for concerns about wound closure
Reasons to avoid directly grasping tumor with instruments
- lead to tissue fragmentation and exfoliation of tumor cells
- crush artifact on histopathology
What is a common tumor type for pseudocapsules?
Soft Tissue Sarcomas
What are the two types of ionizing radiation used?
Electrons and X-rays
Electron radiation is good for what types of tumors?
Superficial
Characteristics of X-ray (photon) radiation
- skin-sparing
- penetrate deeper
What unit is used for measuring “dose” of radiation?
Gray (Gy)
What % of the biologic effect of RT comes from free-radical formation?
70%
Why do we give several small doses of radiation rather than one large one?
- repair-normal cells repair but dose accumulates in tumor cells because they cannot repair
- repopulation of cells depleted by RT
- Reoxygenation-since 70% of DNA damage is induced by free-radical formation, oxygenation of tumor is important
- reassortment (of tumor cells through cell cycle)
Radiation is prescribed based on _________?
normal tissue tolerance
Acute toxicity(radiation) characteristics
- within weeks
- targets rapidly proliferating tissues
- painful/unpleasant
- self-limiting
How many patients and within what time frame generally develop late toxicity effects of radiation?
1-5% within three years
Characteristics of late toxicity from radiation
- years later
- target slowly-dividing tissues
- irreversible, progressive, and difficult to treat-can be fatal
What constitutes a high total dose of radiation?
42-57 gray
General protocol for definitive-intent RT
- daily (M-F) treatments for 3-4 weeks
- small dose per fraction (2.25-4.2 Gy)
General protocols for palliative-intent RT
- daily (M-F) treatments for a week at 4 Gy per fraction
- weekly treatments for 3-6 weeks at 6-8 Gy per fraction
What type of treatment usually works best against microscopic disease?
chemotherapy
What is one systemic form of cancer that chemo is a good treatment for?
multicentric lymphoma
How is metronomic chemo administered?
small, frequent doses orally
How is MTD chemo administered?
high doses, infrequently, IV or oral
What type of chemo is directly cytotoxic?
MTD
Toceranib phosphate (Palladia), masitinib, and mesylate (Kinavet) are examples of ______
tyrosine kinase inhibitors
How do TKIs work?
inhibition of VEGF, PDGF, c-Kit, etc.
What is the route of administration for TKIs?
oral; this is appealing to owners however these drugs still have potentially dangerous side effects and require intense monitoring
What is the incidence of side effects with chemotherapy?
about 30% of cases; only 5% very severe (hospitalization )
Why is diarrhea sometimes a side effect with chemo?
GI mucosal inflammation and damage
Patients receiving chemo sometimes vomit as a side effect due to activation of ______
CRTZ or CNS vomiting centers
Most important bone marrow side effect of chemo
neutropenia; some drugs have a delayed second nadir at ~21 days
Cyclophosphamide unique toxicity
sterile hemorrhagic cystitis
Doxorubicin unique toxicities
- extravasation reactions
- cardiotoxic-dogs
- nephrotoxic-cats
Cisplatin unique toxicity
pulmonary effects-cats
L-asparaginase unique toxicity
allergic/anaphylactic
CCNU/lomustine unique toxicity
hepatotoxic
Prednisone may induce drug resistance by what mechanism?
induces MDR gene
Which class of anti-inflammatories are good for carcinomas?
NSAIDs
Which class of anti-inflammatories are good for lymphoma?
steroids
What are some palliative measures that could be done in a patient with cancer that is having difficulty breathing/sleeping?
- bronchodilators
- intranasal vasoconstrictors (Afrin)
- palliative RT
How does the canine melanoma vaccine work?
DNA plasmid encodes tyrosinase which allows antibodies against tyrosinase to be produced which is helpful since tyrosinase is involved in the production of melanin
Route of administration for melanoma vaccine
transdermal
IL-2 is recombinant from _______ and marketed for ________(tumor type)
canarypox; feline injection-site sarcomas
Steroids are sometimes used as intralesional therapy for _____
MCTs
What are some definitive treatment options for canine appendicular osteosarcoma?
- amputation
- limb-sparing surgery
- stereotactic radiation therapy
What are some palliative treatments for canine appendicular osteosarcoma?
- palliative RT
- bisphosphonates
- pain management
Lifespan of RBCs in dogs & cats
dogs: 120 d
cats: 70d
Lifespan of platelets
5-10d
Lifespan of granulocytes
4-8 hours
