Introduction

Canine nasal tumors are one of the more common tumor types in dogs representing up to 1% of all cancers. The majority are carcinomas including adenocarcinomas, squamous cell carcinoma and undifferentiated carcinomas. The remaining include fibrosarcomas, chondrosarcoma and osteosarcoma, but occasionally lymphoma, mast cell tumors, malignant melanoma, hemangiosarcoma and other pathologies are diagnosed. They are characterized by local invasion with inflammatory infiltration consisting of neutrophils, macrophages and plasma cells and low metastatic rates with local lymph nodes and lungs being the most common metastatic sites.

Patients are most often >10 years of age and present with progressive signs of nasal disease such as unilateral nasal discharge, episodes of epistaxis and sneezing as well as deformity of the nasal bones. If there is invasion of the cribriform plate neurological signs may be part of the clinical presentation. Despite the addition of CT and MRI as imaging modalities for the nasal cavity, imaging alone is not enough for a positive diagnosis and imaging features cannot identify particular tumor pathologies.

Therefore, one of the major challenges is still to get an adequate tissue sample to allow a more precise diagnosis to guide the choice of therapy. Obtaining a biopsy often requires invasive measures and as bleeding can be a complication hemostasis testing such as thromboelastography (TEG) or a coagulation profile is often recommended.

The majority of research over the past 5–10 years has focused on advanced imaging techniques including PET-CT and their ability to discern specific nasal tumor pathologies as well as optimizing radiation therapy (RT) protocols through the use of IMRT (intensity­ modulated RT).

Standard of Care?

Diagnosis: Preferentially a tissue biopsy should be obtained for histopathology, but under some circumstances cytology samples may be accepted.

Clinical staging prior to initiation of therapy: A minimum database (MDB) consisting of a complete hemogram including blood smear evaluation, biochemistry, and urinalysis, nasal and thoracic imaging by either X-ray, but preferentially CT or MRI as these are superior to conventional radiography of the nasal cavity in delineating extent of tumor. A study has showed no advantage of MRI over CT and CT has the advantage of providing information on bone lysis, whereas others have shown no difference.

Therapy: Radiation therapy (RT) is the treatment of choice supported by several studies also in recent years. The expected survival at 1 year ranges from 43–68% and the 2-year survival ranges from 11–44%. Most RT protocols involve 10–18 treatments delivered in 3–4.2 Gy fractions.

Chemotherapy have shown inferior to radiation therapy, but may be considered when RT is not available or as rescue treatment after RT. Various chemotherapeutic protocols have been reported, including single agent cisplatin and multi agent doxorubicin, cisplatin and piroxicam. Recent studies have reported protocols utilizing mitoxantrone in combination with NSAIDS, and adjuvant therapy with local slow releasing carboplatin gel after cytoreduction.

Response evaluation criteria: restaging 6 and 12 weeks after RT including if possible a minimum database (MDB) consisting of a complete hemogram including blood smear evaluation, biochemistry, and urinalysis, nasal and thoracic imaging by preferentially CT.

Follow-up: Every month for one year and every three months thereafter: physical examination and CT q6 months. If suspicion of relapse confirmation by cytology or histopathology.

On the Horizon

The future diagnosis and management of canine nasal cavity tumors likely will include molecular diagnostic techniques, molecular imaging (PET-CT, PET-MRI and potentially also HyperPET) to guide IMRT as well as species specific immune therapeutic approaches.

References

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