Page 656 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

634 PART IV Specific Malignancies in the Small Animal Patient

30 days and, in one report of 76 dogs, most dogs were eutha-
nized at the time of diagnosis. 134,200 If therapy is attempted,
effort is generally made to control local disease in addition to
VetBooks.ir locoregional and distant metastases, although therapy is con-
sidered largely palliative. There is currently no standard-of-care
consensus therapy for canine prostate tumors, although use of
nonsteroidal antiinflammatory drugs (NSAIDs) is recommended
as minimal therapy.
Therapeutic options for managing local disease include par-
tial or total prostatectomy, electrosurgical transurethral resection
(TUR), photodynamic therapy (PDT), RT, laser therapy, and
medical management. Prostatectomy is generally recommended
for dogs with early stage, intracapsular disease, but case selection is
likely important for good outcome. Total prostatectomy is associ-
A
ated with a moderate to high rate of postoperative morbidity and
a survival benefit over medical management has not been investi-
gated. 148,228–233 The entire prostate gland and associated urethra
are removed with total prostatectomy, thus requiring reconstruc-
tion for urinary drainage. The most common complication is uri-
nary incontinence, occurring in 33% to 35% of dogs. 148,231,232
A recent multiinstitutional retrospective study described total
prostatectomy in 25 dogs that included 9 dogs with extracapsular
extension of tumor and 11 dogs with intracapsular tumors. All
dogs survived prostatectomy and 21 received variable adjunctive
therapy, most commonly mitoxantrone and NSAIDs (n = 14). 148
The MST for all dogs was 231 days and dogs with intracapsular
tumors had a significantly longer MST than those with extracap-
sular tumors (248 days vs 138 days). 148 Local recurrence and/
B or distant metastasis were suspected in over 30% of dogs, thus
justifying the prospective exploration of surgery and additional
• Fig. 29.7 (A) Cytology from a prostatic carcinoma (4×) demonstrating local and systemic therapy for some dogs. 148 Subtotal intracap-
clusters of variably sized polygonal epithelial cells with a moderate amount sular prostatectomy may be a useful alternative in some dogs. In
of basophilic cytoplasm, which often contains clear, nonstaining vacuoles. one study that compared 10 dogs that underwent total prosta-
(B) Cytology from a prostatic carcinoma (20×) showing cellular detail and tectomy to 11 dogs that underwent subtotal intracapsular pros-
moderate anisocytosis and anisokaryosis. Cells have round to ovoid nuclei tatectomy, the latter procedure was associated with longer mean
with a coarsely granular chromatin pattern and distinct nucleoli. (Images STs (112 days vs 20 days) and a decreased rate of postoperative
courtesy Dr. D. Seelig and Dr. D. Heinrich, University of Minnesota.)
complications. 230 Importantly, 7 of the 10 dogs that underwent
total prostatectomy were euthanized within 2 weeks of surgery
support for its effect on prognostication. 134,225 Cytologic evalua- compared with only two dogs in the subtotal intracapsular prosta-
tion of samples collected via traumatic catheterization or prostatic tectomy group. 230 The high acute (within 2 weeks) postoperative
wash may prove challenging, as it can be difficult to differentiate mortality rate in dogs that underwent total prostatectomy in this
dysplastic epithelial cells from neoplasia. 213,226 In one study, dis- randomized study may be reflective of less stringent case selection
cordant results between cytology and histology in prostatic dis- given the results of the more recent report of total prostatectomy
orders occurred in 20% of cases, but were not considered a flaw in dogs. 148,230 As urinary incontinence is common after prostatec-
of aspiration techniques but rather of the pathologic process. 213 tomy, attempts have been made to reduce trauma to the prostatic
Multiple techniques were employed, including ultrasound-guided urethra, including use of a neodymium:yttrium–aluminum–gar-
FNA, prostatic massage and wash, and impression smears of biop- net (Nd:YAG) laser; however, there is still a risk of significant
sies. Other factors, such as serum and seminal plasma concentra- postoperative complications. 229,232,233 Rapid palliation of dysuria
tions of acid phosphatase (AP), prostate-specific antigen (PSA), was reported after TUR using an electrocautery cutting loop with
and canine prostate-specific esterase, have not been useful in the or without intraoperative RT in three dogs with prostatic TCC or
definitive diagnosis of PCA in the dog. 133,227 Although signifi- undifferentiated carcinoma. 212 Complications occurred in all dogs
cantly higher serum total AP, prostatic AP, and nonprostatic AP and included urinary tract infection, tumor seeding, and urethral
concentrations were noted in dogs with PCA compared with perforation, and STs were relatively short. 212
healthy dogs or dogs with BPH, they were neither sufficiently sen- In dogs with urethral obstruction due to a prostatic tumor,
sitive nor specific for definitive diagnosis. 227 palliative measures may be attempted to alleviate the obstruc-
tion. Placement of a cystostomy tube permits urinary diver-
Treatment and Prognosis sion and bladder emptying, but owners should be aware that
it generally does not resolve incontinence or stranguria and
Because PCA in dogs is characterized by insidious local progres- secondary urinary tract infections are common. 234–236 Pallia-
sion and a high rate of metastasis, most dogs are diagnosed with tive stenting of the urethra in the obstructed area is a reason-
advanced disease and the overall prognosis is poor. Median sur- able alternative to cystostomy tubes and is the authors’ preferred
vival times (MSTs) for dogs without therapy are often less than option. The extent and location of the obstruction is determined