Another antineoplastic agent that has been evaluated to treat mammary carcinoma belongs to the platinum family. The adjuvant
use of carboplatin has been anecdotally reported to provide a median duration of remission of 436 days and median survival
time of 535 days, with 40% of cats alive at two years.46 The single-agent use of carboplatin appears to be well-tolerated, with only mild to moderate hematologic and gastrointestinal
toxicity noted in treated cats.46
In summary, given the high metastatic potential of feline mammary carcinomas, the adjuvant use of systemic chemotherapy after
radical mastectomy is recommended to maximize survival times. Additionally, systemic chemotherapy may have a limited role
for the palliative management of macroscopic, nonresectable primary tumors, but future prospective studies should be performed.
Other treatment options
Although surgery and systemic chemotherapy are considered the cornerstones of therapy, other treatment modalities may also
benefit feline cancer patients.
Attempting to harness the host's immune response against feline mammary carcinoma has been attempted, but response to treatment
with biologic response modifiers has been poor.47,48
Palliative radiation therapy likely has a role in providing pain relief from nonresectable, ulcerative mammary carcinomas,
as well as in delaying local regrowth from residual microscopic disease.
The judicious use of analgesics should be considered for patients suffering from large bulky disease, ulcerated tumors, or
painful metastases, such as to bone. Although many analgesics are considered off-label for use in cats, medications such as
nonsteroidal anti-inflammatory drugs and opioids may be beneficial for the supportive management of these advanced-stage patients
(see "Understanding and recognizing cancer pain in dogs and cats" and "Treating cancer pain in dogs and cats" in the May 2005
issue of Veterinary Medicine).
PROGNOSIS
Table 3 Selected Prognostic Factors for Mammary Cancer in Cats
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Without treatment, cats are likely to die of their disease within a year.5,39 The most important prognostic factors include tumor size, extent of surgery (when comparing radical with conservative surgery),
histologic grade, and lymph node metastasis (Table 3).
Tumor size
Tumor size has been the most important prognostic factor for recurrence and survival in most studies.12,16,39,48,49 In one sentinel investigation, cats with smaller tumors treated with surgery alone had longer disease-free intervals and
median survival times than did cats with tumors larger than 2 cm in diameter (Table 3).39 A comparable relationship is also observed in male cats with mammary carcinoma, with a median survival time of 14 months
for tumors less than 2 cm in diameter and a median survival time of less than two months for tumors greater than 3 cm.10 These collective findings advocate early surgical intervention in any cat presenting with a mammary mass.
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