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Small Animal Medicine II > Systemic Cancer Therapy > Flashcards

Systemic Cancer Therapy Flashcards

1
Q

When is chemotherapy considered a preferred treatment? What cells does it target?

A

systemic disease —> metastasis

rapidly dividing cells - GI crypt, bone marrow, hair

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2
Q

What are the mechanisms of action of akylating agents, mitotic spindle inhibitors, and antitumor antibiotics? What are some examples of each?

A

adds an alkyl group to DNA, causing strand breaks —> cyclophosphamide, chlorambucil

attach to microtubules during mitosis —> vincristine, vinblastine

inhibit topoisomerase II, intercalate DNA, and cause free radical formation —> doxorubicin, mitoxantrone

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3
Q

What are the mechanisms of action of platinum drugs, antimetabolites/nucleotide analogs, and chemotherapeutic enzymes? What are examples of each?

A

binds platinum to DNA —> carboplatin

incorporates altered nucleotides into DNA during S phase —> Tanovea

depletes body of asparagine necessary for cell division —> L-asparaginase

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4
Q

How is the GI system affected by chemotherapy? What signs does this result in?

A

damages the crypt cells, resulting in shortened crypts, blunting of villi, and reduced absorption

decreased appetite, vomiting, and diarrhea 2-3 days post-treatment (time it takes for the damaged crypt cells to migrate up)

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5
Q

What treatments are recommended to relieve GI signs?

A

usually mild and self-limiting, hospitalization not usually necessary

  • decreased appetite = Cerenia, Mirtazapine, Entyce
  • vomiting = Cerenia, Ondansetron
  • diarrhea = Metronidazole, fluids
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6
Q

How does chemotherapy affect the bone marrow? What does this result in? What does not occur?

A

damages bone marrow precursors

neutropenia and thrombocytopenia with the nadir at around 7-10 days (time it takes for circulating cells to die) —> rebound leukocytosis seen after!

acute anemia —> RBCs have a longer lifespan, allowing them to circulate longer

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7
Q

Is treatment common necessary for neutropenia and thrombocytopenia resulting from chemotherapy treatment?

A

only if a fever develops

  • low grade (103-104.5) = antibiotics (TMP-S, marbofloxacin, clavamox) +/- fluids
  • high grade (>104.5) = hospitalization, IV antibiotics and fluids, Neupogen (exogenous GCSF to stimulate neutrophil growth)
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8
Q

Why is Neupogen not commonly given to patients with neutropenia caused by chemotherapy?

A
  • expensive
  • rebound neutrophilia typically results after nadir
  • most hospitals don’t carry a stock and by the time a delivery comes in, rebound neutrophilia would likely occur
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9
Q

What side effect can be seen around the catheter site with chemotherapy treatments?

A

extravasation injury —> severe damage to perivascular tissues if drug leaks outside of the vein during administration (not all drugs!)

  • can be severe enough to require amputation
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10
Q

What treatment is recommended for extravasation injuries? What is a drug-specific antidote available?

A
  • pull back on plunger to clear the line of the drug
  • place a warm compress for mitotic spindle inhibitors or a cold compress for others to keep the drug from spreading

Dexrazoxane for Doxorubicin

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11
Q

What breeds most commonly develop hair loss in response to chemotherapy? What can happen in cats?

A

breeds with continuous (anagen phase) hair growth —> Poodles, Bichon Frise, Schnauzers, OESD (clipped hair can regrow slowly)

lose whiskers and guard hairs, resulting in a “chemo coat” of softer hair

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12
Q

What specific side effect is seen with Doxorubicin? What should be done in at-risk patients?

A

cardiotoxicity due to myocardial damage from free radicals, resulting in irreversible DCM, decreased fractional shortening, and (supra)ventricular arrhythmias (dose-dependent)

pre-treatment echo, especially in Boxers and Dobermans

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13
Q

What specific side effect is seen with Cyclophosphamide? What signs does this result in?

A

sterile hemorrhagic cystitis caused by the metabolite, acrolein (dogs!)

hematuria, pollakiuria, dysuria a few days after treatment

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14
Q

How can sterile hemorrhagic cystitis be avoided with Cyclophosphamide treatment? How is it treated?

A

give Furosemide to dilute acrolein

  • get a urine culture and treat infection if present
  • NSAIDs, prednisone
  • oxybutynin - relax detrusor
  • DMSO
    (can take months to heal or be permanent)
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15
Q

What specific side effect is seen with Vincristine treatment? What signs are seen?

A

paralytic ileus due to peripheral neuropathy in dogs and cats

cessation of peristalsis results in restlessness, pacing, painful abdomen, anorexia, vomiting, and tenesmus within 7-10 days post-treatment

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16
Q

How is paralytic ileus due to Vincristine treatment treated?

A

metclopramide (prokinetic) + supportive care

17
Q

What specific side effect is seen with CCNU (Lomustine) treatment? What signs are seen?

A

hepatotoxicity in dogs —> delayed chronic hepatopathy

usually no clinical signs, but can result in elevated ALP and ALT

  • ALT more concerning
18
Q

How can hepatotoxicity as a result of CCNU treatment be prevented?

A
  • Denamarine pre-treatment
  • decrease dose, increase time between treatments
  • discontinue if ALT is elevated
19
Q

What are 2 specific chemotherapies not recommended for cats? Why?

A
  1. Cisplatin - pulmonary edema (cisplat splats cats!)
  2. 5-Fluoruracil - neurotoxicity

FATAL

20
Q

What is metronomic chemotherapy? When is it typically used?

A

daily low-dose oral chemotherapy administration to attain anti-angiogenic effects, rather than cytotoxicity —> blocks receptors responsible for formation of new blood vessels, like COX-2 and VEGF, and damages endothelial cells

  • HSA
  • osteosarcoma
  • soft tissue sarcoma
  • SCC
  • TCC
21
Q

What are the 3 most common chemotherapies used as metronomic therapy? What are they commonly combined with?

A
  1. cyclophosphamide (Cytoxan)
  2. chlorambucil (Leukeran)
  3. CCNU (Lomustine)

NSAIDs for further anti-angiogenic properties - Piroxicam, Deramaxx, etc.

22
Q

What is the mechanism of action of tyrosine kinase inhibitors? What 2 are used in veterinary medicine?

A

bind to various tyrosine kinase receptors on the surface of cancer cells to induce anti-angiogenic effects

  1. Palladia (toceranib)
  2. Masivet (masitinib, not available in US)
23
Q

What method of administration is used for Palladia? What is it used to treat? What side effects are commonly seen?

A

oral —> Mon/Wed/Fri

originally curated for MCT treatment, but is now used for carcinomas > sarcomas

  • GI - decreased appetite, vomiting, GI ulceration, diarrhea
  • BW - neutropenia, thrombocytopenia, hypoalbuminemia
  • UA - proteinuria, azotemia

Small Animal Medicine II (57 decks)

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