Abstract
Background: Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer in dogs. Despite this, relatively few reports of this disease exist pertaining to prognostic factors and outcome.

Aim: To evaluate factors associated with survival in dogs with all subtypes of HCC diagnosed on histopathology.

Methods: A retrospective single institutional study was performed on 94 client owned dogs with a histopathologic diagnosis of HCC between 2007 and 2018 obtained by biopsy (21/94) or attempted definitive resection (73/94). Signalment, preoperative features, surgical findings, and postoperative outcomes were recorded. Associations between survival to discharge and collected data was performed by univariable logistical regression. Kaplan-Meier survival analysis was performed to identify negative risk factors for long-term prognosis.

Results: The median survival time (MST) for all patients was 707 days (95% CI = 551-842). MST was not significantly different (P > 0.05) between patients who had suspected versus incidentally diagnosed HCC (695 days versus 775 days), between complete versus incomplete surgical margins (668 days versus 834 days), or between patients with massive subtype vs nodular/diffuse subtype (707 days vs 747 days). Logistical regression identified an association with excision of the right medial lobe and risk of perioperative death (OR=9.2, CI 1.5-55.9, P=0.016). An ASA score ≥4, disease present within the quadrate lobe, and elevated blood urea nitrogen, potassium or gamma-glutamyltransferase, were identified as negative prognosticators during multivariable cox regression. Preoperative imaging (ultrasound or CT) agreed with the surgical location in 91% of cases. Preoperative cytology was consistent with a diagnosis of HCC in 15/32 (46.9%) of cases.

Conclusion: Type of diagnosis (incidental vs presumed), completeness of excision, and subtype were not associated with MST in this study. Preoperative identification of tumors within the central division may be related to a less favorable outcome. Results of preoperative cytology were not highly sensitive for identifying a malignancy.

Key words: Cancer, Canine, Hepatocellular carcinoma, Liver, Survival analysis