Treatment of indolent cutaneous T-cell lymphoma with hypofractionated radiation therapy in three cats.

Background: Feline indolent cutaneous T-cell lymphoma (ICL) is an uncommon neoplastic disease. There is currently no consensus on treatment recommendations for ICL.

Objective: To report the clinical outcome of three cats with ICL treated with hypofractionated electron-beam radiotherapy (RT).

Animals: Three privately owned cats with ICL.

Materials And Methods: Medical records and client surveys were reviewed. A diagnosis of probable ICL was based on history, clinical presentation and histopathological findings, and confirmed using CD3 immunohistochemical analysis and PCR for antigen receptor gene rearrangement (PARR). All cats were treated with hypofractionated RT (four fractions of 8 Gy).

Results: All cats presented with skin lesions characterised by erythema and alopecia that were refractory to previous treatment with systemic glucocorticoids. Before 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 showed histological improvement defined by decreased infiltration of lymphocytes, with cellular infiltrate present only in the deeper dermis; one cat had near complete histological resolution of lesions with only minimal residual lymphocytes. One cat was determined to have a complete clinical response while the other showed partial responses. No acute adverse effects of radiation were observed; chronic effects included leukotrichia, partial alopecia and mild fibrosis. All clients reported improvement in quality of life for their cats.

Conclusions And Clinical Importance: Clinical and histological improvement in these cats suggests that hypofractionated RT can be a useful treatment modality for cats with ICL.