Lecture 11 2/19/25 Flashcards
What are the indications for chemotherapy in animals?
-most effective single therapy for some malignancies such as lymphoma
-delay or prevent metastasis for highly metastatic tumors after surgery
-palliation for non-resectable tumors
-shrinkage of large tumors prior to surgery
What are the principles of chemotherapy?
-chemo kills rapidly dividing cells
-chemo is not targeted; collateral damage to normal tissue leads to chronic side effects
-common side effects include bone marrow suppression, alopecia, and GI upset
What are the characteristics of cytotoxic chemotherapy?
-aka maximally-tolerated dose chemo
-directly kills dividing tumor cells
-causes collateral damage
-tumor cells grow between doses
When is the cytotoxic chemo approach best?
when the majority of cancer cells can be cleared very rapidly (such as with surgery) and chemo is used as a secondary treatment for remaining cells
What is the goal of cytotoxic chemo?
long term control
What are the characteristics of metronomic chemotherapy?
-low-dose chemo
-does not kill tumor cells
-less side effects
-less expensive
-can be given at home
What is the goal of metronomic chemo?
tumor stabilization
How does metronomic chemo work?
-inhibiting angiogenesis
-activating immune system
How is chemo dosing done?
based on body surface area/mg/m^2
What is the most important concept regarding chemo dosing?
we ALWAYS round down (even 10.9kg becomes 10kg)
What are the general adverse effects of chemo?
-bone marrow suppression
-alopecia
-GI signs
Why is neutropenia the most common dose-limiting toxicity in chemotherapt?
-neutrophils are essential to innate immune system
-first line of defense against infection, especially bacterial
-shortest half life of all WBCs
What must be evaluated on blood work prior to chemo?
-HCT: no contraindication to treatment, but should be evaluated
-neutrophils: must be greater than 2500 for chemo
-platelets: must be greater than 150,000
What are interpretations when checking neutrophil nadir/lowest count?
-if neutrophils are greater than 1000 patient does not need intervention
-if neutrophils are less than 1000 patient does need intervention; predisposes to infection and sepsis
What are the possible interventions for neutrophil counts less than 1000?
-oral antibiotics for 5 to 7 days if no clinical signs or fever
-hospitalization with IV antibiotics if sick or fever present
-decrease chemo dose for next treatment
What are the characteristics of thrombocytopenia as a chemo side effect?
-typically a chronic side effect because of longer half life
-rarely clinical
What are the characteristics of anemia in oncology patients?
-common, but not typically due to chemo because of long life-span
-typically see a non-regenerative anemia due to inflammation
What are the characteristics of alopecia from chemo?
-chemo targets hair in anagen phase
-breeds with continuously growing hair coats are most affected (curly/wire hair)
-hair can grow back in different colors/textures
What are the characteristics of GI signs from chemo?
-crypts have rapidly dividing cells
-signs occur within 3 to 5 days of treatment
-can see vomiting, diarrhea, and anorexia
What is important regarding the MDR1 gene mutation?
-encodes a drug efflux pump
-helps cells get rid of various chemo drugs
-defective pumps lead to increased intracellular drug concentrations
-patients experience increased side effects and possibly death
Which breeds are at risk for the MDR1 mutation?
-australian shepherd
-mini australian shepherd
-collie
-long-haired whippet
-sheltie
-german shepherd
What should be done in preparation for chemo in breeds predisposed to the MDR1 mutation?
-run a blood test to ID mutation before chemo
-decrease chemo dose in heterozygous animals by 25% and escalate if tolerated
-recognize that there is no safe dose in homozygous animals
What are the general characteristics of drug extravasations?
-some drugs can cause local tissue reaction if accidentally given SQ
-prevention is key
How is drug extravasation prevented?
-have two experienced personnel for admin.
-place IV cath. first
-use only 0.9% NaCl flush
-no IV pumps
-constant monitoring of site for extravasation
What are the immediate steps to take in the event of possible extravasation?
-stop infusion
-leave IV cath or butterfly in place
-aspirate back drug
-plan further treatment
What are the effects of extravasation of vincristine and vinblastine?
-indirect effects similar to burns
-causes erythema, swelling, edema, and ulceration
What are the steps to handling vincristine/vinblastine extravasation?
-goal is to disperse and dilute
-stop infusion and aspirate back drug
-use warm pack to disperse drug
-administer hyaluronidase
What are the effects of extravasation of doxorubicin?
-direct effect
-progressive tissue destruction
-causes skin blistering, ulceration, necrosis, and tissue sloughing
-can progress to the point of needing surgery or amputation
What are the steps to handling doxorubicin extravasation?
-goal is to localize and neutralize
-stop infusion and aspirate back drug
-use cold pack to keep drug from spreading
-administer dexrazoxane/zinecard ASAP
What are the steps to chemo safety in the clinic?
-verify doses with multiple checks
-use biosafety hood and closed system transfer devices to draw up chemo
-wear gloves, gown, and mask PPE
-prevent pregnant, TTC, nursing, or immunocompromised staff from participating in chemo admin.
What are the steps to chemo safety for owners?
-inform owners that drugs are present in urine and feces for up to 72 hours after admin.
-advise owners to wear gloves when administering meds and cleaning up after pet
-advise owners to never crush/split/liquify drugs
