PET-CT identifies recurrence of sinonasal adenocarcinoma

This patient underwent PET-CT imaging approximately 14 months following stereotactic radiation therapy (SRT) and completion of six cycles of carboplatin chemotherapy because of intermittent nasal congestion, sneezing and mucoid nasal discharge.

PET-CT imaging was recommended to evaluate for active cancer, assess for metastatic disease, and further investigate the liver abnormalities.

While conventional imaging can reveal structural changes, it may not always distinguish between active cancer, scar tissue, treatment-related changes or inflammation. PET-CT combines anatomical and metabolic imaging, allowing veterinarians to determine whether abnormalities exhibit increased metabolic activity, a feature typically associated with malignancy.

The patient underwent a whole-body PET-CT scan using F18-fluorodeoxyglucose (F18-FDG), a radiotracer that highlights areas of increased glucose metabolism. Imaging was performed approximately 60 minutes following intravenous administration of the tracer.

Physiological uptake was observed in expected tissues, including the brain, salivary glands, heart, abdominal organs and urinary system, confirming appropriate tracer distribution and scan quality.

For this patient, PET-CT identified a contrast-enhancing soft tissue mass occupying both nasal passages, extending caudally into the nasopharynx. The lesion caused extensive bilateral turbinate destruction and progressive osseous lysis, including involvement of the right maxillary bone, osseous margins of the nasopharynx and the pterygoid hamulus.

The tumour demonstrated extension beyond the nasal cavity with invasion of adjacent soft tissues, including portions of the medial pterygoid muscle, and apparent protrusion into the oral cavity. While most of the lesion demonstrated only mild FDG uptake, the nasopharyngeal component exhibited moderate metabolic activity (SUVmax 7.1), consistent with viable recurrent neoplastic tissue.

Importantly, no abnormal FDG uptake or enlargement was identified within the regional mandibular or retropharyngeal lymph nodes, indicating no evidence of locoregional nodal metastasis.

Whole-body staging revealed no pulmonary nodules, intrathoracic lymphadenopathy or evidence of distant metastatic disease. The abdomen and musculoskeletal system were also unremarkable, with no clinically significant abnormalities identified.

For referring veterinarians, PET-CT offers an advanced imaging modality that can distinguish active cancer from treatment-related changes, thereby improving confidence in both diagnosis and post-treatment monitoring. For pet owners, it can provide reassurance that treatment has been successful while ensuring any remaining health concerns are appropriately investigated.

We are currently accepting referrals. Pet owners can contact their vet directly and request a referral to Pet Theranostics.