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