Nasal Lymphoma with Low Mitotic Index in Three Cats Treated with Chlorambucil and Prednisolone

SIMPLE SUMMARY: Nasal lymphoma is the most common type of cancer of the nasal cavity in cats. Nasal lymphoma in cats is usually treated with injectable chemotherapy and/or radiation therapy if it is localized to the nasal cavity. These treatments require significant commitments in both time and finances from the owner. In this case series, we report three cats with nasal lymphoma with a low mitotic index, treated with oral chlorambucil and prednisolone, with two of them achieving a relatively good survival time. ABSTRACT: Lymphoma is the most common tumor of the nasal cavity in cats. Commonly used treatment modalities are radiotherapy and chemotherapy, or both. Typical chemotherapy protocols used in cats with nasal lymphoma are COP (cyclophosphamide, vincristine prednisolone) and CHOP (cyclophosphamide, doxorubicin, vincristine and prednisolone). Thus far, the use of single-agent chlorambucil in nasal lymphoma has been evaluated in a single case report. We report a case series of three cats with B cell nasal lymphoma, two cats with intermediate cell, and one large cell, all with a low mitotic index (MI) of less than 5 mitotic figures per ×400 field, treated with chlorambucil and prednisolone. Two of the cases achieved a long disease-free interval, while the one with the highest MI did not. Protocols using chlorambucil and prednisolone may have potential as a first-line therapy for feline nasal lymphoma cases with a very low mitotic index.