Page 641 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 28 Tumors of the Mammary Gland 619

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A B

C

• Fig. 28.6 (A) Cat having mammary adenocarcinoma prepared for bilateral simultaneous chain mastec-
tomies. (B) Intraoperative view after excision of all mammary tissue. (C) Immediate postsurgical appear-
ance after the bilateral chain mastectomies. (Courtesy Dr. Julius Liptak, VCA Canada—Alta Vista Animal
Hospital, Ottawa, Canada.)

intramammary injection of iopamidol and radiographic imaging Several studies, all retrospective, have evaluated the use of che-
after intramammary ethiodized oil injections. 111 There are no motherapy in cats with mammary cancer. Two case series of cats
clinical reports utilizing nuclear lymphoscintigraphy in the cat. with macroscopic primary and/or metastatic tumors documented
Use of blue dyes for node visualization is recommended with objective responses in 40% to 50% of the cats treated with a com-
caution because their use may cause Heinz body anemia and bination of DOX and cyclophosphamide. 224,225 The relatively high
methemoglobinemia in this species. LNs extirpated during mas- response rate in the macroscopic setting suggests that this may be
tectomy surgery frequently yield metastasis, as found in 48 of an effective protocol in patients with microscopic minimal residual
51, 204 41 of 93, 222 and 17 of 66 218 cats having surgical resection disease (i.e., after surgical cytoreduction). Results from adjuvant
of malignant MGTs. studies are, however, mixed, but two more recent studies suggest a
Fibroepithelial hyperplasia has a classic appearance that is benefit from chemotherapy in cats undergoing radical mastectomy
very difficult to mistake for malignant MGTs. This condition (chain or bilateral). The chemotherapy varied in these studied, but
is typically treated with either OHE or medical hormone ther- DOX-based protocols were used most commonly in both of these
apy management. Inflammatory mammary carcinoma has very studies: cats treated with chain mastectomy and adjuvant chemo-
rarely been reported in cats; in a sole case series of three cats, therapy survived significantly longer than cats treated with chain
the disease was described as occurring secondary to postsurgi- mastectomy alone (1998 days vs 414 days). 202 Similar findings were
cal mastectomy with nonhealing incisions, edema, and suture also demonstrated in a separate multiinstitutional study whereby
rejections. 200 the disease-specific survival was significantly improved for 53 cats
receiving adjuvant chemotherapy in 105 cats being followed after
Systemic Treatment mastectomy. 222 These results support the use of adjuvant chemo-
Early detection and aggressive surgery (including prophylactic therapy in this setting. It is interesting that none of these retrospec-
chain mastectomy) can result in long-term survival in cats with tive studies reported STs as long as earlier studies using surgery
early stage MGTs; however, cats with delayed diagnosis, large pri- alone, especially in the subset of cats with small tumors. This fur-
mary tumors, or metastatic local LNs are not treated effectively ther illustrates the difficulty in comparing outcomes between retro-
with surgery alone. The incidence of distant metastasis, primarily spective studies, especially noncontemporaneous ones. Ultimately,
to the lungs and pleura, is high, although other organs are also prospective, randomized trials will be necessary to determine the
frequently involved. 199 Despite the high rate of metastasis after appropriate use of chemotherapy in cats with MGTs. Despite the
surgery, relatively few advances have been made in identifying lack of quality evidence in the literature to support it, veterinary
effective adjuvant systemic treatments. oncologists continue to recommend the use of chemotherapy in
Owing to low HR expression in feline mammary carcinoma, some cats with MGTs. Table 28.8 summarizes the most important
hormonal therapy is not likely to be effective; however, random- prognostic factors, general guidelines for systemic treatments, and
ized trials have not been performed to confirm this. the strength of supporting evidence.