Introduction

Feline indolent cutaneous T-cell lymphoma (ICL) is an uncommon neoplastic disease. There is currently no consensus on treatment recommendations for ICL. The objective is to report the clinical outcome of three cats with ICL treated with hypofractionated radiotherapy (RT).

Methods

Medical records and client surveys were reviewed. ICL was diagnosed based on histopathology and further confirmed using immunohistochemistry and PCR for antigen receptor rearrangement (PARR). All cats were treated with hypofractionated RT (4 fractions of 8 Gy).

Results

All cats presented with skin lesions characterized by erythema and alopecia that were refractory to previous treatment with systemic glucocorticoids. Prior to hypofractionated RT treatment, lesions were histologically described as having diffuse infiltration of the dermis with CD3+ T cells. Molecular clonality analysis revealed clonal T-cell receptor gamma gene rearrangement. After RT, two cats had histologic improvement defined by decreased infiltration of lymphocytes, with cellular infiltrate present only in the deeper dermis; one cat had near-complete histologic resolution of lesions with only minimal residual lymphocytes. One cat was determined to have complete clinical response with resolution of erythema and hair re-growth. Two cats had partial clinical responses, of which one cat developed progressive disease 202 days after RT, with skin lesions including pruritus and ulceration. No cats had clinically relevant adverse events secondary to RT. All clients reported improvement in their cat’s quality of life.

Conclusion

Clinical and histologic improvement in these cats suggests that hypofractionated RT can be a useful treatment modality for cats with ICL.