Malignant mammary tumors: Biologic behavior, prognostic factors, and therapeutic approach in cats - Veterinary Medicine
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Malignant mammary tumors: Biologic behavior, prognostic factors, and therapeutic approach in cats
Most mammary tumors in cats are malignant, and metastasis is common. The prognosis depends on how far the cancer has spread and the tumor's biologic behavior, among other things. Find out how to improve the outcome in these critically ill cats.


VETERINARY MEDICINE


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
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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