Case Report: Long term multimodality treatment of canine hepatocellular carcinoma with serial monitoring of serum alpha-fetoprotein.

A 13-year-old spayed female Shih Tzu presented with a several-month history of progressively increasing liver enzyme activities concurrent with managed hyperadrenocorticism. Diagnostic imaging revealed a solitary hepatic mass originating from the caudate process of the caudate lobe adhering to the caudal vena cava. Hepatocellular carcinoma (HCC) was confirmed via histopathological examination of an ultrasound-guided tru-cut biopsy, accompanied by a markedly elevated serum alpha-fetoprotein (AFP) concentration. Molecular targeted therapy with olaparib was initiated since complete surgical resection was unachievable due to tumor adherence to the caudal vena cava and conventional chemotherapy has limited efficacy for canine HCC, based on genomic profiling. Following objective tumor progression and worsening mass effect after 2 months, cytoreductive surgery was performed. Postoperatively, olaparib and canine interleukin-15 (cIL-15) immunotherapy were instituted to control potential micrometastases. The patient achieved clinical and radiographic stability for a 10-month follow-up period, accompanied by a significant drop in serum AFP levels. However, following the discontinuation of cIL-15 and subsequent reduction of olaparib dosage because of suspected adverse effects, serum AFP levels rebounded progressively, and tumor recurrence was confirmed via ultrasonography. The patient died 20 months after the initial detection of the mass. This case describes the clinical course of canine HCC managed with a multimodal therapeutic approach and highlights the potential utility of serum AFP as an adjunctive biomarker for disease monitoring.