Page 498 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

476 PART IV Specific Malignancies in the Small Animal Patient

of AGASAC cells was associated with a longer MST (1168 days)
1.0
No metastasis than in dogs whose AGASAC expressed E-cadherin in fewer than
624
75% of cells (448 days).
VetBooks.ir 0.8 and without hypercalcemia were 256 days and 584 days, respec-
Metastasis
In a study of 113 dogs with AGASAC, MSTs for dogs with
tively. 600 Although hypercalcemia is a poor prognostic factor
600,602,607
other studies have found no differ-
in some studies,
Proportion surviving 0.6 dogs. 599,605,606,609 Dogs with hypercalcemia require complete or
ence in survival between hypercalcemic and normocalcemic
near-complete removal of the tumor burden, including metastatic
Tumor responses
disease, to resolve the hypercalcemia.
603,613,637
0.4
to hypofractionated RT and toceranib have resulted in resolution
Medical management
611,617,640
of hypercalcemia in some dogs.
with corticosteroids and/or bisphosphonates may be needed to
0.2 improve control of hypercalcemia. Recurrence of hypercalcemia
after tumor-ablating treatment is typically associated with recur-
rent or metastatic disease. 600,603,614
In 11 dogs with anal sac melanoma treated with various combi-
0.0
nations of surgery, RT, chemotherapy, immunotherapy, and sup-
0 500 1000 1500 2000 portive medical management, the median PFI and OST were only
Time (days) 3 months and 3.5 months, respectively. 560 Ten of 11 dogs died due
• Fig. 23.34 Estimated Kaplan–Meier survival curves for overall survival to local or distant tumor progression. 560 One dog with a small, 1.5
times in dogs with apocrine gland anal sac adenocarcinoma with (dashed) cm primary tumor survived at least 58 months after surgery and
and without (solid) metastasis at the time of diagnosis. The median over- adjuvant chemotherapy. 560 Six of nine dogs with anal SCC sur-
all survival times for dogs with metastasis (448 days) was significantly vived 0 to 7 months after diagnosis. 561–563 Two dogs were lost to
shorter than for dogs without metastasis (761 days, p = 0.042). (Reprinted follow-up 7 months after diagnosis and one dog was disease-free
with permission from Wouda RM, Borrego J, Keuler NS, et al. Evalua- 1 year after treatment with hypofractionated RT and carboplatin
tion of adjuvant carboplatin chemotherapy in the management of surgi- for a recurrent SCC. 561–563 Of five dogs that underwent surgical
cally excised anal sac apocrine gland adenocarcinoma in dogs. Vet Comp
Oncol. 2016;14:67–80.) resection of the primary tumor, four dogs had recurrence within 1
to 5 months of surgery. 561,563
The MST for 30 cats treated surgically, with or without adjunc-
range from 293 to 448 days and this is significantly worse than tive chemotherapy and/or RT, is 260 days. 566 The 1-, 2-, and
the MSTs of 529 to 1205 days for dogs without LN metas- 3-year survival rates were 42%, 27%, and 18%, respectively, with
tasis. 601,605,606 Dogs with LN metastasis at the time of diag- a tumor-related mortality rate of 53%. 566 Poor prognostic factors
nosis have a 2.3-fold increased risk of tumor-related death. 605 for survival in treated cats with AGASAC include local tumor
Although the prognosis is worse for dogs with LN metastasis, 601 recurrence and increased nuclear pleomorphic score. The risk of
MSTs improve after excision of the metastatic LNs. 601 The role tumor-related death increased by 8 times for cats with local tumor
of chemotherapy in dogs with LN metastasis disease remains recurrence and 10 times for cats with increased nuclear pleomor-
undefined. The MST for dogs with distant metastasis ranges phic score. 566 The MSTs for cats with a nuclear pleomorphic score
from 71 to 82 days in one study to 219 days in another study, of 2 and 3 were 909 days and 187 days, respectively, and this was
and this is significantly worse than the MST in dogs without significantly different. 566 The role of chemotherapy and RT are
distant metastasis. 600,601 unknown, but RT would theoretically be indicated because of the
Treatment also has an effect on STs in dogs with AGASAC. high rate of local tumor recurrence, especially after incomplete
Overall, when considering all dogs with AGASAC, those treated histologic excision. A short-lived partial response to carboplatin
with surgery have a significantly better outcome (MST 548 days) was reported in one cat with recurrent AGASAC. 644 In another
than those treated with either chemotherapy (MST 202 days) report, adjuvant curative-intent RT (48 Gy) and carboplatin
or those for which surgery was not part of the treatment proto- resulted in local recurrence and/or metastasis within 6 months of
col (MST 402 days). 600 However, when dogs with advanced LN treatment in two cats. 567 In both cats, RT was well tolerated with
metastasis (>4.5 cm) were expressly evaluated, treatment with minimal acute effects. 567
hypofractionated RT resulted in significantly better outcomes
compared with surgical extirpation. 611 Comparative Aspects 645–648
AGASAC has been classified histologically according to its
tumor cell arrangement, including solid, rosette, tubular, pap- No similar hormonally dependent perianal disease state exists in
illary, and mixed patterns. 607,608 In one study of 39 dogs, dogs humans. The most common cancer of the anal margin is squa-
with a predominantly solid pattern had shorter PFIs and OSTs mous cell (epidermoid) carcinoma. These tumors arise from the
compared with dogs with other histologic patterns, corroborat- junction of haired skin and mucous membrane of the anal canal.
ing a prior study that also associated tumor-related death with Risk of developing cancer in this location is positively correlated
solid histologic pattern. 607,608 Other histologic features of the with sexual activity, and most tumors are associated with human
primary tumor that have been associated with shorter PFIs and papillomavirus infection. Precancerous changes (dysplasia) in
OSTs include increased peripheral infiltration into surrounding the epithelium of the anal canal may precede tumor develop-
tissue, presence of necrosis, and lymphovascular invasion. 607 In ment. Regional LNs are the most common site of metastasis.
an IHC study, the expression of E-cadherin in greater than 75% Previously considered a surgical disease requiring a permanent