Survival and Disease-free Interval of Cats with Mammary Carcinoma Treated with Chain Mastectomy

Abstract

Background: Mammary tumors are extremely common in cats and have high metastatic rates with poor prognosis. The main objective of the present study was to evaluate the disease free interval and survival in cats undergoing radical mastectomy as sole therapy.Materials, Methods & Results: Twenty cats with mammary tumors and no evidence of distant metastasis were studied. General health and concomitant diseases were assessed by clinical and hematological examination. Thoracic radiographs and abdominal ultrasonography were performed to evaluate thoracic and abdominal metastases. All cats underwent chain mastectomy, which was unilateral when tumor was present in one mammary chain, and bilateral in steps if tumors were present in both mammary chains. Intact cats were spayed. An elliptical incision was made around the mammary chain with a three centimeter margin around tumor. Regional lymph node was removed. Mean age was ten years, and 14 cats were mixed breed, three were Persian and two were Siamese. Fifteen cats were spayed at tumor diagnosis, but only three had been spayed before one year old. The inguinal mammary glands were the most affected, followed by abdominal and thoracic glands. Histopathology diagnosed well-differentiated adenocarcinoma in eight cases, moderately differentiated adenocarcinoma in nine cases, poorly differentiated adenocarcinoma in two cases and carcinoma in situ in one case. Most tumors were grade II, and regional lymph node metastasis was present in two cases. Disease free interval ranged from 120 to 1800 days, with an average of 678 days. Four cats had tumor local recurrence and six developed lung metastasis. The survival time ranged from seven to 1800 days, with an average of 768 days. Twelve cats are still alive with no tumor recurrence.Discussion: The average age of onset of mammary carcinomas in cats was ten years old, similar to previous studies. Siamese cats have more risk of developing this disease, but mixed breed cats were frequent in this study. Intact or late spayed cats are predisposed to mammary tumors because of hormonal stimulation, the same was observed in this study. Inguinal and abdominal glands were most affected, similar to other reports. The histopathologic diagnosis was adenocarcinoma in most cases of this study, mostly grade II tumors, which was also observed in previous papers. Regional lymph nodes (axillary or inguinal) should always be removed during mastectomy in cats, as regional metastasis at diagnosis is common, even when not clinically palpable, as was observed in two cases. Distant metastasis occurs most often to the lungs, leading to severe dyspnea. In this study, four cats had local tumor recurrence and six developed lung metastasis. Aggressive and early surgical intervention is the treatment of choice for feline mammary tumors. Unlike dogs (where conservative mammary resections are appropriate in some cases), radical chain mastectomy is recommended for feline mammary tumors, as significantly reduces the risk of local recurrence. In this study, all animals underwent radical mastectomy, without previous cytology or biopsy. Survival is variable between studies, ranging from 220 to 1408 days. Several factors may be involved in disease free intervals and survival times, as tumor size, tumor histological grade, presence of metastasis at diagnosis, type of surgery performed, presence of concomitant diseases and adjuvant chemotherapy. In this study, mean survival time was 768 days and 12 cats are still alive and in follow-up, which may increase this number. This study supports that, if treated early and agressively, cats with malignant mammary tumors can have long survival after chain mastectomy.

Consensus for the diagnosis, prognosis and treatment of feline mammary tumors

“…In Brazil, a breed predisposition was not observed (CUNHA et al, 2016), as opposed to a previous international study that found Siamese cats to be more predisposed to mammary tumors (SORENMO et al, 2013). This fact is likely due to the domestic feline population in Brazil being predominantly composed of mongrel cats (CUNHA et al, 2016).…”

“…The regional, axillary and inguinal, lymph nodes, even if not clinically altered, should be excised at the time of mastectomy due to the high incidence of regional metastases (CUNHA et al, 2016). For the axillary lymph node lymphadenectomy (Figure 4), Patent Blue dye (2.5%) is applied intradermally at a dose of 2 mg/kg, without exceeding the volume of 1 ml per patient, to facilitate the identification and removal of the lymphatic tissue.…”

<b>Valor prognóstico de parâmetros clinico-patológicos e dos subtipos moleculares nos carcinomas mamários em felinos</b>

“…Animais da raça siamesa apresentam maior chance do desenvolvimento precoce da doença, por volta dos 9 anos de idade, além de ser uma raça mais predisposta quando comparada às demais (ZAPPULLI et al, 2015). No entanto, um estudo realizado no Brasil não demonstrou esta predisposição racial, onde a maior parte dos animais acometidos não apresentavam raça definida (CUNHA et al, 2016).…”

>b<Avaliação de marcadores imunohistoquímicos de resistência à múltiplas drogas nos carcinomas mamários em felinos>/b<

“…No entanto, a sobrevida destes animais pode variar de alguns meses até um ano, com uma variação média de 7,7 até 12 meses (OVERLEY et al, 2005;CUNHA et al, 2016…”

“…frequente nesta espécie(TOGNI et al, 2013). Alguns estudos estabelecem a raça Siamesa como predisponente ao câncer mamário(ZAPPULLI et al, 2005), porém outros não demonstram esta relação, talvez pela heterogeneidade de raças na população estudada(CUNHA et al, 2016). Os animais mais acometidos…”