Introduction

Invasive urothelial carcinoma (iUC) is the most common neoplasia of the urinary tract in canines. Patients typically present with non-specific clinical signs such as dysuria, pollakiuria and hematuria and are treated for a urinary tract infection (UTI). When there is little to no response to antibiotic therapy further diagnostics are performed (radiographs/abdominal ultrasound [AUS]) and a mass is discovered.

The most common location of iUC is the trigone region of the urinary bladder. It can also extend into/affect the urethra and also involve the prostate in male dogs. At diagnosis approximately 20% of patients present with metastatic disease and at death at least 50% have metastatic disease. The prognosis of a patient with iUC is dependent on the extent of disease at diagnosis and has an overall median survival time of 6–12 months.

History

Lily was an 8-year-old, female spayed Shih Tzu that initially was presented to the referring veterinarian (rDVM) in July 2020 for urinary issues. The owner reported that she was urinating more and was tender in her abdomen. She was treated off and on for chronic UTIs for 3 months with little response to antibiotic therapy. Abdominal radiographs revealed cystoliths in the urinary bladder and Lily was started on a commercial urinary diet. Her clinical signs continued to worsen and in October repeat radiographs and ultrasound were recommended. Radiographs revealed a periosteal reaction on the right wing of the ileum. AUS revealed a mass like structure in the lumen of the urinary bladder, thickened urethra and enlarged medial iliac lymph nodes (heterogenous in appearance).

Diagnosis/Treatment

In October 2020, Lily was presented to the PUVH oncology service for workup of a urinary bladder mass with probable metastatic disease to the right ileum. The owner reported that she was still doing okay at home. She was eating, drinking, and urinating normally (great urine stream). Her current medications included 25 milligrams (mg) marbofloxacin once daily, 100 mg gabapentin every 12 hours, and 20 mg grapiprant once daily. The owner was concerned that Lily was painful in her pelvic limbs. She did not want to be picked up and would shake when standing. She was laying around more than normal and was not interacting with the owner as much.

On presentation Lily acted uncomfortable. She had a hunched posture, stiff gait and would lay down unless made to rise. She was also noted to pant constantly and would cry out with abdominal palpation. She was assigned a Colorado State University (CSU) pain score of 3. It was clear that she needed more aggressive pain control. The owner authorized further diagnostics which included thoracic and abdominal imaging, cystoscopy, and hospitalization for better pain control.

Radiographs revealed multiple lung nodules and bone lesions in the vertebrae, both ileum and sacrum. AUS revealed urethral thickening, enlarged medial iliac lymph nodes and a hepatic nodule. Following imaging an IV catheter was placed and Lily was moved to the intensive care unit (ICU). She was started on a 3 micrograms (mcg)/kilogram (kg)/hour (hr) constant rate infusion (CRI) of fentanyl overnight. A 0.1 mg/kg infusion of zoledronic acid was also administered to help with pain.

The following morning there was no change in Lily’s CSU pain score and appeared to have some windup present. Her fentanyl CRI was increased to 4mcg/kg/hr and she was started on a maintenance rate of a balanced crystalloid. Lily was anesthetized for a cystoscopy and during prep it was noted that her mass was extending out of the urethra into the vulva. Multiple biopsies were taken from the urethra and a fine needle aspirate (FNA) performed on the right wing of the ileum. Cytology of the urethra and ileum were both carcinoma. Lily was diagnosed with a high grade iUC via histopathology.

Treatment with chemotherapy was started immediately on Lily due to her large tumor burden. She was administered 250 mg/m2 of carboplatin IV. The plan was to discontinue the grapiprant and then start her on 0.3 mg/kg piroxicam after a 6-day washout period. Amantadine was started at 2 mg/kg daily, along with codeine sulfate at 2 mg/kg every 8 hours, and gabapentin was continued.

Lily received 3 doses of carboplatin and zoledronic acid at 3-week intervals. The owner reported at her second visit that she was doing much better and was comfortable. She was allowing them to pick her up and was more social. Prior to her 4th dose in January 2021, she was restaged. She was still doing well at home with no complications from her treatment. The owner did note that she did seem a little uncomfortable more recently and thought it was because she was due for an infusion of zoledronic acid. On staging it was noted that there was progression of her disease (lung nodules, bone lesions, new caudal abdominal mass). The owner was offered palliative care verse trying another chemotherapy. Vinblastine was administered at 2 mg/m2 IV along with a dose of zoledronic acid.

Lily received a total of 3 doses of vinblastine. She tolerated the drug well with no side effects. At each visit she started to become increasingly more painful. After her 3rd dose the owner chose to stop chemotherapy and continue palliative care at home. It was stated that her clinical signs were not improving. Lily was humanely euthanized with the rDVM on February 17, 2021.

Conclusion

Lily’s prognosis at diagnosis was poor due to her advanced disease on presentation. She was given a median survival time of 3–4 months. Pain control is the top priority for patients with bone metastasis. Lily made the team focus more on patient cues/behaviors and taught the team how to better advocate for the patient. Based on the clinical improvement in several patients with bone metastasis, the oncologist chose carboplatin as the treatment of choice.

Reference

1.  Vail DM, Thamm DH, Liptak JM. Withrow and MacEwens Small Animal Clinical Oncology, 6th ed. Philadelphia, PA: Saunders an imprint of Elsevier Inc.; 2020:645–652.