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Staging
- visual and digital assessment
- MDB
- always assess regional lymph nodes - affected in up to 80% cases
- pulmonary mets occur more frequently than lymph node mets - military
pattern in radiographs - doesn't matter which mammary gland is affected
- pleural surfaces may be involved.
- liver mets - about 25% in one study
- bone mets, lameness from appendicular mets, rib and thoracic may be asymptomatic, bone marrow can be infiltrated
- other soft tissue organs - spleen, kidney, adrenal gland, peritoneal surfaces, heart - mets reported
- CNS mets one cat
WHO Stage | Description | Median Survival after Surgery (months) | I | T<1cm, no N | 29 | II | T<1cm, N or T= 1-3 cm +-N | 12.5 | III | T>3cm or T<3cm + N | 9 | IV | any T or N with M | 1 |
1. Most important prognostic criteria : TUMOUR SIZE Tumour size | Median Survival | < 2 cm diam | 36+ months | 2-3 cm | 24 months | > 3 cm | 6 months | 2. Lymph Node involvement (Yes - 6 months vs. No - 18 months median survival) 3. Histologic parameters (MI (mitotic index), cell pleomorphism, tubule formation) Category | Prevalence | 1 Year Survival |
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| (following simple/regional resection) | Well differentiated | (13%) | 100% | Moderate | (60%) | 42% | Poor | (27%) | 0 |
4. Biologic Parameters
- Proliferation status (Ki-67 AgNOR expression - number of silver staining regions).
- High proliferation count > 5.9 -12% cats survived one yr after nonradical resection.
- Low proliferation count < 4.2 -88% survived one year.
- Vimentin expression (poor prognosis in humans) not studied in cats.
Treatment
1. Surgery. Radical, unilateral or staged
bilateral mastectomy is the procedure often recommended due to
malignant nature of most mammary tumors in cats and the likelihood of
multiple tumors within different glands. Radical resection produced
better local control but was not better than regional or simple
mastectomy in terms of overall survival. Therefore, local or regional
mastectomy may be considered if the tumor involves the most caudal or
cranial glands on one side, if there are favorable prognostic factors
or if follow-up therapy (chemotherapy) will be instituted. Draining
lymph nodes should be excised. The axillary node may be difficult to
identify but the inguinal lymph node should always be removed and
submitted for histopathologic evaluation. Cats with small lesions or
tumours that have not invaded the basement membrane (i.e. carcinoma in
situ) may be cured by surgery - definitve surgery should not be delayed
for these cats. Always submit entire specimen for evaluation of
surgical margins.
2. Chemotherapy.
Adriamycin (Doxorubicin) alone or Adriamycin/Cytoxan
(Doxorubicin/Cyclophosphamide) combined have been associated with
significant reductions in tumor volume in the majority of cats treated.
This implies the potential for pre-operative treatment of feline tumors
to significantly downstage the local disease. Current dosage
recommended is 1mg/kg IV every three weeks for five total treatments.
Major side effect is anorexia.
Other chemotherapeutic
compounds have not been evaluated thoroughly. Carboplatin may help -
not studied. Paclitaxel anecdotal efficacy. Vincristine and
methotrexate appear ineffective. Cyclophosphamide alone has no effect.
Improved survival following adjuvant chemotherapy in cats with mammary cancer has also not be definitively confirmed.
3. Hormonal therapy. Since the majority of cats do not possess significant estrogen receptors, antiestrogenic therapy is not likely to be of value.
4. Radiation therapy.
Little information exists to determine the effectiveness of radiation
therapy for feline mammary cancer. Response of human breast cancer to
irradiation, however, indicates a potential role in feline mammary
cancer - but due to the risk of radiation damage to underlying tissue
(lungs, kidneys) only shallow penetrating low energy radiation can be
safely utilized.
5. Immunotherapy. Has
not been shown to help. Post surgical therapy with Corynebacterium
parvum, or Streptococcus pyogenes + Serratia marcescens, or levamisole
(5mg/kg po 3Xweekly), or liposome-encapsulated
muramyl-tripeptide-phosphatidyl ethanolamine (L-MTP-PE) did not improve
outcome.
6. Supportive care. No
pain, no nausea, no starve - quality of life. Analgesia (NSAIDs,
fentanyl patches), anti-emetics, antacids, supplemental feeding (incl.
placing a feeding tube at surgery), appetite stimulants, SQ fluids.
Prevent weight loss. Eat anything just must eat. Treat concurrent
disease - kidneys, heart, triad.
7. Non-domestic Felids.
Generally not treated, it seems. Prevention may be more realistic goal
- don't use progestins for contraception - consider ovariohysterectomy
(spaying) these cats. Analgesics are essential in palliative care.
Prednisone unlikely to palliate neurological signs or help
significantly. Sources: - Rodney Page; Prognostic Factors for Canine and Feline Mammary Cancer, WSAVA 2001
- Gregory K. Ogilvie, Antony S. Moore; Feline Oncology, a comprehensive guide to compassionate care , 2001, VetLearnSystems
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