Oncology Flashcards
What is the metastatic rate of Sertoli cell tumors? What percent of dogs display signs of feminization?
<15% metastatic rate
> 50% of dogs display signs of estrogen overproduction (feminization), including bone marrow suppression (the most deleterious); more likely in retained testicles
Bilateral orchiectomy is the treatment of choice; feminization signs resolve typically within 1-3 months
For what tumor types is histopathologic grade a prognostic indicator?
Cutaneous mast cell tumors Soft tissue sarcomas Lymphoma Mammary carcinoma Pulmonary carcinoma Multilobular osteochondrosarcoma (MLO) \+/- Melanoma (oral, cutaneous, digital)- more so histologic features that are prognostic such as mitoses, pigmentation, Ki67 index
Which cells (in the cell cycle) are most responsive to radiation therapy?
Cells in late G2 or M phase are most sensitive/responsive
Cells in late S-phase are most resistant
What cells are most responsive to metronomic chemotherapy?
Proliferating endothelial cells are most sensitive (hence the use of metronomic chemotherapy for its anti-angiogenic properties)
Which chemotherapy drugs/drug class result in metaphase arrest?
Antimicrotubule agents such as the vinca alkaloids (vincristine, vinblastine, vinorelbine)
What is the most common secondary brain tumor?
Hemangiosarcoma
What is the mechanism behind platelet dysfunction in patients with multiple myeloma?
The malignant plasma cells produce an overabundance of immunoglobulin (M component), which inhibits platelet aggregation and the release of platelet factor-3 (helps with prothrombin > thrombin conversion).
Other mechanisms for bleeding diathesis in MM (besides platelet dysfunction):
1) Thrombocytopenia from myelophthisis
2) Adsorption of minor clotting proteins
3) Generating abnormal fibrin polymerization
4) Producing a functional decrease in calcium
What tumors can be associated with a paraneoplastic myasthenia gravis?
Thymoma (most common), less commonly osteosarcoma, biliary carcinoma, lymphoma, oral sarcoma
Which chemotherapy drugs can cross the BBB?
Lomustine (CCNU) Cytosine arabinoside (Cytosar) Temozolomide (Temodar) 5-fluorouracil (5-FU) Hydroxyurea Procarbazine
What is the mechanism behind the development of sterile hemorrhagic cystitis (SHC) with cyclophosphamide administration?
How do you prevent SHC from occurring with treatment?
The metabolite, acrolein, causes irritation to the bladder mucosa.
Incidence is reduced with co-administration of furosemide, and encouraging water intake and frequent urination for 24-48 hours after administration. Mesna is co-administered in humans, but not in veterinary medicine.
What is the mechanism of action of diazoxide in the treatment of insulinoma?
Inhibits closure of ATP-dependent K+ channels in beta-pancreatic cells > prevents depolarization of beta-cells and inhibits opening of voltage-dependent Ca++ channels > decreased Ca++ influx results in decreased exocytosis of insulin-containing secretory granules
Also increases glycogenolysis and gluconeogenesis, and inhibits uptake of glucose by tissues
What are the most common biochemical abnormalities you would see with tumor lysis syndrome?
Hyperkalemia, hyperphosphatemia, hyperuricemia, hypocalcemia
Which chemotherapy drugs are p-glycoprotein substrates, and thus must be reduced (or avoided) in dogs with MDR1 (ABCB1) mutations?
Vinca alkaloids (vincristine, vinblastine), doxorubicin
Which two chemotherapy drugs should never be used in cats, and what clinical syndromes do they cause in cats?
5-FU - neurotoxicity
Cisplatin - fatal pulmonary edema
What chemo drug causes mast cell degranulation?
Doxorubicin
