Overview

• Prostatic adenocarcinoma is a malignant tumor that occurs in both neutered and intact male dogs.
• Although this neoplasm represents <1% of all canine malignancies, it is the most common prostatic disorder in neutered male dogs.
• Metastases to regional lymph nodes, lungs, and the lumbosacral skeleton are common. Skeletal metastases can adopt an osteoblastic appearance.

Signalment

• Dog and rarely cat
• Medium- to large-breed intact or neutered male dogs
• Median age of 9–10 years

Signs

Causes & Risk Factors

Neutered males are at increased risk for prostatic neoplasia

Differential Diagnosis

• Other primary neoplasia (i.e., squamous cell carcinoma, transitional cell carcinoma).
• Metastatic or locally invasive neoplasia (i.e., transitional cell carcinoma).
• Acute or chronic prostatitis, benign prostatic hypertrophy, prostatic abscess, and prostatic cysts are possible differentials in intact male dogs but are highly unlikely in neutered dogs.

CBC/Biochemistry/Urinalysis

• Inflammatory leukogram possible.
• Alkaline phosphatase may be high if skeletal metastases exist.
• Post-renal azotemia may be present if urethral obstruction exists.
• It is prudent to evaluate urine samples via cystocentesis and free-catch techniques, as hematuria, pyuria, and malignant epithelial cells may be observed in free-catch samples but are unusual in samples obtained by cystocentesis.

Other Laboratory Tests

Serum and seminal plasma markers such as acid phosphatase, prostate specific antigen, and canine prostate specific esterase are not elevated in dogs with PAC.

Imaging

• Thoracic radiography-metastases may appear as pulmonary nodules or increased interstitial markings.
• Abdominal radiography-sublumbar lymphadenomegaly, mineralization of the prostate, lytic lesions to the lumbar vertebrae or pelvis as a consequence of direct tumor extension from regionally infiltrated lumbar lymph nodes may be seen.
• Abdominal ultrasonography-focal to multifocal hyperechogenicity with asymmetry and irregular prostatic outline, ± prostatic mineralization.
• Contrast cystography may help differentiate prostatic from urinary bladder disease.

Diagnostic Procedures

• Prostatic aspirate (percutaneous or transrectal).
• Prostatic wash.
• Prostatic biopsy performed percutaneously or surgically.
• Percutaneous biopsy has been associated with tumor seeding along the biopsy tract.

Drug(s)

• Chemotherapy-carboplatin, mitoxantrone, or doxorubicin; may offer short-term benefit.
• Pain relief with NSAIDs, morphine-derived drugs.
• Aminobisphosphonates for the relief of painful skeletal metastases.
• Stool softeners to relieve tenesmus.

Contraindications/Possible Interactions

N/A

Patient Monitoring

Ability to urinate and defecate, pain secondary to skeletal metastases, quality of life.

Prevention/Avoidance

Keeping dogs sexually intact may decrease risk.

Possible Complications

• Urethral obstruction
• Metastasis to regional lymph nodes, skeleton, and lungs

Expected Course and Prognosis

Guarded to poor, survival of 2–6 months depending upon presenting clinical symptoms. Treatment early in the course of disease with curative-intent radiation and systemic chemotherapy can extend survival times to 12 months.

Associated Conditions

None

Age-Related Factors

None

Abbreviations

• NSAID = nonsteroidal anti-inflammatory drug
• PAC = prostatic adenocarcinoma