Chemotherapy

From Cat

The fundamental biochemical and genetic differences between feline cancer cells and normal cells are not clearly understood. Clinically useful drugs achieve a degree of selectivity on the basis of certain characteristics of cancer cells that can be used as pharmacologic targets. Combination antineoplastic chemotherapy offers many advantages. Drugs with different target sites or mechanisms of action are used together to enhance destruction of tumour cells. Antineoplastic agents that act primarily on rapidly dividing and growing cells produce multiple side effects or toxicities, including bone marrow or myelosuppression, GI complications, and immune suppression. Patterns of toxicity may be either acute or delayed. Acute toxicities often include GI complications such as nausea, vomiting, anorexia, and diarrhoea. Allergic reactions and anaphylaxis may also be of immediate concern with selected drugs. Delayed toxicities may develop days to weeks after antineoplastic therapy. Myelosuppression, a common delayed toxicity, can be life-threatening due to the increased incidence of infection associated with leukopenia, increased risk of haemorrhage associated with thrombocytopenia, and anaemia. Other important delayed toxicities include tissue damage associated with extravasation of selected drugs, alopecia caused by hair follicle damage, and stomatitis or ulcerative enteritis. Adverse effects on spermatogenesis and teratogenesis may be of concern in breeding animals.

Combination chemotherapy allows killing of tumour cells by several mechanisms. CBC assessment should be performed prior to and 1 week after each therapy until a pattern indicates that each agent is safe and well tolerated. If a serious side effect occurs, subsequent doses of that drug should be reduced by 10-15%.


Drug Indications Dose cats Preparation Administration
Actinomycin D lymphoma, FIP 0.5 - 0.9 mg/m2 single injection given weekly a 4
Adriamycin lymphoma, osteosarcoma, hemangiosarcoma, carcinoma <10 kg:1 mg/kg 10 mg vials Diluted in saline over a minimum of 15 mins via an IV catheter
Bleomycin Lymphoma, squamous cell carcinoma 10 µg/m2 IV or SQ or intralesionally 15 IU/mL every 24 hours for 4 days, then weekly; max dose 200mg/m2
Busulfan Leukemia 0.1 mg/kg 6 mg/mL one tablet daily for 4-6 weeks
Carboplatin Fibrosarcoma, squamous cell carcinoma 150-200 mg/m2 50 mg and 150 mg vials Diluted in saline over a minimum of 15 mins via an IV catheter
Carbimazole Hyperthyroidism 5 mg/kg daily 5 mg tabs Give orally once daily
Chlorambucil Gingivitis, lymphoma 15 mg/m2 2 mg tablets 4 day pulse treatment repeated every 3 weeks
Cisplatin Fibrosarcoma 50 mg/mL vial 100 mg/m2 every 4 weeks x 2
Cyclophosphamide Lymphoma 50 mg/m2 25 mg and 50 mg tablets Give orally once daily for four days
Cyclosporin Thrombocytopenia 4 - 6 mg/kg 10 mg tabs Give orally once daily
Cytarabine Myelomonocytic leukemia 30 - 50 mg/kg every 24 hours
Dacarbazine Melanoma, lymphoma 200 - 250 mg/m2 IV Give every 24hrs for 5 days, every 21 days
Soft tissue sarcomas 1000 mg/m2 IV infusion over 6 - 8hrs, every 21 days
Decitabine Leukemia 400 - 800 mg/m2 50 mg vial Give IV or SQ every 24 hrs x 10 days
Deuterium depletion[1] Adjuvant 25+/-5 ppm Orally Give ad lib in conjunction with other oral chemotherapy agents
Doxorubicin lymphoma, osteosarcoma, hemangiosarcoma, carcinoma <10 kg:1 mg/kg 10 mg vials Diluted in saline over a minimum of 15 mins via an IV catheter
Imatinib Mast cell tumours[2], fibrosarcoma[3] 10 mg/kg 10 mg capsules Given orally once daily until remission
Lomustine Leukemia 60 mg/m2 10 mg and 40 mg capsules Give orally in one dose every 4 weeks
Methimazole Hyperthyroidism 5 mg/kg daily 5 mg tabs Give orally as needed
Mitoxantrone Lymphoma, oral SCCs, transitional cell carcinoma 6.0 - 6.5 mg/m2 IV 2 mg/mL vial once every 3 - 4 weeks x 4 - 6 times
Prednisolone Anti-inflammatory, immunosuppression 10 mg/day 5 mg tablets Give orally from day 1
Sorafenib Renal carcinoma 2 mg/kg 100 mg caps Give orally once daily
Vincristine Lymphoma, pheochromocytoma, leukemia, plasmacytoma, haemangiosarcoma 0.5-0.7 mg/m2 1 mg/mL vials bolus IV via an IV catheter

The protocol with the highest first remission rate (69%) and highest remission duration (615 days) and survival time (510 days) is chlorambucil and prednisolone. This is followed by the protocol combination of COP (cyclophosphamide, oncovin, prednisolone) with a remission rate of 75% and remission duration of 150 days.

The Modified Wisconsin protocol (Modified CHOP) includes L-asparaginase, vincristine, cyclophosphamide, chlorambucil, doxorubicin, prednisolone and methotrexate and purports a remission rate of 68% and survival time of 225 days. Individual veterinarian preference appears to affect protocol choice[4].


Feline Conversion of Body Weight in Kg to Body Surface Area

Kg Square metres (m2)
0.5 0.06
1.0 0.10
2.0 0.15
3.0 0.20
4.0 0.25
5.0 0.29
6.0 0.33
7.0 0.36
8.0 0.40
9.0 0.43
10.0 0.46
11.0 0.49
12.0 0.52

References

  1. Somlyai G et al (2010) Biological significance of naturally occurring deuterium: the antitumor effect of deuterium depletion. Orv Hetil 151(36):1455-60
  2. Isotani M et al (2010) Mutations in the fifth immunoglobulin-like domain of kit are common and potentially sensitive to imatinib mesylate in feline mast cell tumours. Br J Haematol 148(1):144-153
  3. Katayama R et al (2004) Imatinib mesylate inhibits platelet-derived growth factor activity and increases chemosensitivity in feline vaccine-associated sarcoma. Cancer Chemother Pharmacol 54(1):25-33
  4. August, J.R. (2006). Consultations in feline internal medicine. Elsevier Saunders, Missouri