Palliative Chemotherapy Shows Promise for Feline Carcinoma of Unknown Primary
Carcinoma of unknown primary, or CUP, is one of those diagnoses that makes even seasoned veterinary professionals pause. Despite advanced imaging, histopathology, and immunohistochemistry, the original tumor site remains elusive. In human oncology, CUP is relatively common and notoriously challenging, accounting for a notable percentage of new cancer diagnoses and carrying a guarded prognosis. In veterinary medicine, especially in cats, documented cases are few, leaving clinicians with limited guidance and a lot of tough conversations. A recently reported feline case offers a meaningful data point and a reminder that palliative care can still deliver measurable wins for both patient and caregiver.
The patient was a 7 year old spayed female Domestic Shorthair cat presented for vomiting and anorexia. Advanced imaging via computed tomography revealed a concerning picture. Multiple masses were identified in the abdomen, liver, and kidneys, along with mild sternal and splenic hilar lymphadenopathy. The extent of disease immediately suggested a metastatic process. Ultrasound guided Tru Cut needle biopsies were obtained for histology and immunohistochemistry. Despite thorough evaluation, results supported a diagnosis of carcinoma of unknown primary. No definitive origin could be identified, placing this case squarely in CUP territory.
With extensive metastases and no surgical options, prognosis was poor. Rather than pursuing aggressive interventions with low likelihood of success, the clinical team and owner opted for a palliative approach. The goal shifted to stabilizing disease progression, managing clinical signs, and preserving quality of life. This decision reflects a growing trend in veterinary oncology. Millennial pet owners in particular often prioritize comfort, transparency, and meaningful time over maximal intervention at any cost.
The cat was treated with a combination of gemcitabine and carboplatin, a protocol more commonly discussed in human oncology and select veterinary applications. The response was encouraging. The patient maintained a good quality of life for approximately four months following initiation of therapy. Hematologic adverse effects were noted, including non regenerative anemia and neutropenia. Importantly, these side effects were manageable with supportive care and did not outweigh the perceived benefits of treatment. For a disease known for poor outcomes and limited options, four months of stable quality of life represents a meaningful result.
This report adds to the sparse veterinary literature on CUP in cats and highlights gemcitabine plus carboplatin as a potential palliative chemotherapy option for non resectable feline carcinomas. While this is a single case and not a controlled study, it provides practical insight for clinicians faced with similar scenarios. It also reinforces the value of palliative oncology as an active, thoughtful treatment pathway rather than a passive alternative. Even when cure is not possible, there is still room to improve comfort, slow disease progression, and support the human animal bond.
Further studies are needed to better define the role of gemcitabine carboplatin protocols across various feline carcinomas and metastatic presentations. Until then, cases like this help expand our collective clinical playbook. For veterinary professionals navigating the gray zones of oncology, this case serves as a reminder that sometimes success is not measured in years, but in good days.
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