Vivek Basu (vet and Aria’s owner), Andy Yale (Lecturer in Veterinary Oncology) and Sandra Guillén (Lecturer in Veterinary Oncology)

Aria, an 11-year-old, female neutered, rough collie, was presented for investigation into chronic vomiting and weight loss. Aria also had a history of hypothyroidism, which was well controlled. Haematology and biochemistry on admission were largely unremarkable. Total thyroxine, cobalamin, folate, and ACTH stimulation tests were also within normal limits.

Abdominal ultrasound showed gastric wall thickening in the region of the fundus and greater curvature of the stomach. Gastroduodenoscopy revealed a focal erythematous lesion in the fundus (Figure 1). Endoscopic biopsies were obtained, and histopathology was suggestive of early gastric adenocarcinoma.

CT of the thorax and abdomen showed no evidence of metastases (See figure 2, below) and following discussion with our Soft Tissue Surgery Service and her carer, Vivek, who is a vet, Aria underwent a partial gastrectomy.

Histopathology confirmed an undifferentiated adenocarcinoma, with vascular and serosal invasion, which had been incompletely excised.

Aria’s vomiting and appetite improved after surgery but given the high metastatic rate reported for this cancer, adjuvant chemotherapy of carboplatin was recommended.

Aria continued to have an excellent quality of life throughout chemotherapy, with only mild side effects seen. After finishing the six-dose carboplatin protocol, ongoing maintenance treatment with toceranib phosphate was elected. However, due to recurrent diarrhoea this was discontinued after nine weeks.

Nine months on

At nine months post-diagnosis, Aria started having sporadic episodes of abdominal pain and retching immediately after eating. A repeat ultrasound of the abdomen showed segmental wall thickening of the small curvature and associated pancreatoduodenal and cranial mesenteric lymphadenopathy.

These findings, together with the clinical signs, were most compatible with tumour recurrence. Aria was then started on rescue chemotherapy with intravenous 5- fluorouracil every two weeks. Multimodal analgesia was also started, with robenacoxib once a day, paracetamol twice a day, and gabapentin twice a day.
Sadly, Aria continued to experience weight loss and abdominal pain despite multimodal analgesia, and humane euthanasia was performed 12 months after her initial presentation.

Case discussion

Gastric carcinomas (GC) account for less than 1% of all canine tumours, although represents one of the most common tumours found in this location in dogs, followed by leiomyo(sarco)ma, gastrointestinal stromal tumours and lymphoma.

Similar to humans, the aetiology of canine gastric carcinomas is complex and poorly understood, but it is believed that both environmental and genetic factors play a role (see reference 1 below) Unfortunately, diagnosis is often made when the disease is at an advanced stage and metastatic disease can be found in up to 70% of dogs.

Limited information is available regarding the clinical outcome of GC after surgical resection, as well as chemotherapy’s role in the progression of this disease. In Aria’s case, the long survival time was unusual, but we believe that the multimodal approach with the combination of marginal tumour excision and chemotherapy may have contributed to it.

In a recent study of dogs undergoing partial gastrectomy +/- chemotherapy, the median survival time was 178 days and administration of chemotherapy was associated with improved survival, but only 7 out of 40 dogs had a survival of more than 10 months (see reference 2 below).

Of those long-term survivors, four dogs received carboplatin based protocols, with two of them also receiving toceranib afterwards. One dog was treated with toceranib only and one dog with mitoxantrone.

Aria underwent three different chemotherapy and molecular targeted therapy protocols, with carboplatin appearing to make the most significant improvement in quality of life. More importantly, her adverse reactions were expected, mild, and well managed on an outpatient basis.

Toceranib has been anecdotally used in dogs with GC based on the overexpression of receptor tyrosine kinases, its antiangiogenic properties, and the responses seen with a similar drug (sorafenib) in humans with GC.

Due to Aria’s higher-than-average survival time and excellent quality of life, it is our authors’ hope that this protocol can be adapted for future similar situations and allow those animals to experience a similar outcome.

Author’s note: Aria is my own dog, she carried me throughout vet school and my career, traveling the globe alongside me. She meant more than words can express, and I hope this case study can be her legacy, helping future generations and continuing to improve the world alongside the joy she brought to everyone that knew her.

References
1. Hugen S, Thomas RE, German AJ, Burgener IA, Mandigers PJJ. Gastric carcinoma in canines and humans, a review. Vet Comp Oncol. 2017 Sep;15(3):692-705.
2. Abrams B, Wavreille VA, Husbands BD, et al. Perioperative complications and outcome after surgery for treatment of gastric carcinoma in dogs: A Veterinary Society of Surgical Oncology retrospective study of 40 cases (2004-2018). Vet Surg. 2019 Aug;48(6):923-932.
3. Miller KB, Lejeune A, Regan R, Szivek A, Kow K. Suspected Carboplatin Extravasation Reactions in Seven Dogs. J Am Anim Hosp Assoc. 2018 Nov/Dec;54(6):360-367