Anal Sac Adenocarcinoma In Dogs

Anal gland adenocarcinoma (AGA) (also known as anal sac adenocarcinoma) is a rare type of cancer of the apocrine glands located in the walls of the anal sacs. These sacs can be found by the anus, more or less at 4 o’clock and 8 o’clock (imagine the back end of dog as a clock face).

This type of cancer reported to represent 17% of perianal tumors in dogs and usually tends to occurs in middle aged to older dogs

AGA has no breed disposition and occurs in both males as well as females. This uncommon cancer tends to be locally invasive in the surrounding tissues and has a high rate of metastasis (spread to distant tissues)

Hypercalcemia (High calcium levels) is reported in approximately 25% of dogs with AGA, which can cause kidney failure.

Symptoms may include:

• Constipation, obstipation, dyschezia, tenesmus
• Scooting
• Excessive licking of the perineal area
• Narrow or ribbon-like stools or blood in stools
• Inflammation or external swelling in the perianal region
• Polyuria, polydipsia

During physical examination, perianal mass enlargement or irregularities may detected with one or both anal sacs.

Dog owners may observe symptoms of kidney failure from the elevated calcium (paraneoplastic syndrome).

These symptoms generally include:

• Increased Thirst And Urination May Occur
• Vomiting
• Lethargy
• Anorexia
• Muscle Weakness

Usually, the following tests are suggested to detect the tumor, evaluate for metastasis and present a clear clinical picture of overall health :

• Aspiration: A small needle aspirate into the anal sac mass to obtain a few cells and cytologic examination can distinguish anal sac adenocarcinoma from other tumor types
• Blood tests: Complete blood count (CBC), serum chemistry panel (including calcium levels), urinalysis
• Abdominal ultrasound and thoracic radiographic examinations: Evidence for metastasis(spread of cancer). Examination to evaluate for regional lymph nodes (sublumbar nodes) or tumor spread into other organs such as liver, kidneys, etc.
• For dogs with small (diameter less than 3cm): primary tumors and if the tumor hasn’t spread, the most appropriate therapy is local surgical excision. Post-operatively to improve the tumor control, radiotherapy may be used.
• Dogs with primary tumors (greater than 3cm), no evidence of metastasis: chemotherapy (e.g. mitoxantrone or carboplatin) can be used to attempt to shrink the tumor. More recently, melphalan is tested to be efficient chemotherpaic agent and Palladia ( tyrosine kinase inhibitors ) was found to be beneficial.
• Again, radiotherapy may be used post-op to reduce the duration of the resulting remission.
• Some dogs have tumours which have spread only to the regional lymph nodes but no further:

This happens in 50% of affected dogs

Surgical removal of enlarged lymph nodes (sublumbar lympadenopathy)

If the lymph nodes appear as if they cannot be removed or if you don’t want to give the dogs any undue risk, they can be left or managed by either radiotherapy or chemotherapy or sometimes by a combination of these. 

When surgical margins are clean (tumor-free microscopically) --- chemotherapy with (once every 3 weeks for 5-6 total treatments post-operatively) is recommended.

If cancer seen microscopically at tumor margins on biopsy (margins are incomplete) then in addition to chemotherapy, radiation therapy is also given.

hypercalcemia (and resultant kidney issues are is present):

Monitoring of creatinine concentrations, blood urea nitrogen  and urine specific gravity

 Vets may suggest sodium chloride diuresis together with furosemide.

calcium lowering drugs (e.g. bisphosphonates) or prednisone is used.

• After surgery, Dog activities should be restricted activity for about 2 weeks to allow recovery and incision healing
• A restrictive collar usage is recommended for 10-14 days. This prevents the natural tendency of dogs to lick and chew at a wound.
• A diet of roughly 50% meat, and 40–50%  whole grains or non-starchy vegetables is optimal.
• home-prepared diet with Dark leafy greens
• Fish oils or fish meals, or whole fish are rich in omega-3 fatty acids.

Although Anal sac adenocarcinoma is inheritable, for instance, spaniel breeds are powerless to fight against it.

We guess that’s a pretty cynical or skeptical approach. Can we do anything-- to prevent it from happening to our dogs in the first place?

So, what a cancer prevention diet for a pet looks like

In general, the breakdown looks like:

High Protein, Good Fats and Low Carbs, antioxidants and cancer fighting nutrients

Dogs: 50% veggies (dark leafy greens, carrots, broccoli, green beans etc are good choices) + 50% protein (chicken or beef is best)

More common in Spaniel breeds, English Cocker Spaniel, English Springer Spaniel, German Shepherd, Golden Retriever, Boxer

• Anal sac tumors occur in male and female dogs with roughly an equal incidence.

• They occur in any breed but are more common in Spaniel breeds.

• The average age of affected dogs is 10 years. Older dogs are most affected.

• With anal sac adenocarcinoma, the average survival time is approximately 12-18 months for dogs. The survival time is typically shorter if there is a metastatic disease or elevated blood calcium without surgery

• Most of the dogs, Anal sacs are the only site where this type of cancer is found, but in some cases, they may spread to the lymph nodes or via the bloodstream to places like the spleen, liver, and lungs.

• When the spread of the cancer is limited to the sublumbar nodes, treatment is still possible.
• Due to the fact that locally invasive nature and a high rate of local metastasis of AGA, If the spread has happened to distant sites such as the liver or lungs, surgery or radiation as a definitive treatment is generally not recommended.  
• In patients with distant spread, treatment is aimed at palliation (hypofractionated radiation therapy) to provide dogs more comfortable by relieving clinical signs).
• hypofractionated megavoltage radiation therapy provides partial regression or stabilization of tumor size with alleviation of clinical signs in 75% of affected dogs.

• Commercial foods should have high-quality, natural ingredients, with no artificial additives.
• Fresh, home cooked, balanced or raw food diet
• Avoid DRY FOOD and go for fresh diet
• Underground vegetables
• Pureed pumpkin 
• Add fiber to your pup’s diet.
• Increase water intake or install a pet water fountain.
• Supplement prebiotics and probiotics formulated for pets.

Regardless of the severity of a diagnosis of malignant cancer, most dogs can enjoy an excellent quality of life with appropriate therapy.

Most favorable prognosis can be expected with early detection and appropriate treatment. This emphasizes the significance of a rectal examination as part of a routine physical examination in all dogs.