Electrochemotherapy-induced Radiation Recall in a Cat

Electrochemotherapy is gaining popularity for the treatment of malignancies of companion animals due to its efficacy and low cost. In this paper, we describe the successful treatment of a recurring fibrosarcoma in a cat by using cisplatin selectively driven within the tumor cells by trains of biphasic pulses. The cat's tumor did not recur over the following five months, however the cat did experience severe erythema at the site of previous irradiation, followed by moist desquamation and ulcer that required debridement and prolonged therapy with steroids and antihistaminic drugs. The symptoms and the response to symptomatic therapy were strongly suggestive of radiation recall. Electrochemotherapy (ECT) should be used with caution in previously irradiated areas. Further studies are warranted in this field due to its potential as a rescue for relapsing tumors. Soft tissue sarcomas (STS) are rather common feline tumors and have local aggressive behavior and a low tendency for distal spread (1-2). The standard therapy following surgical excision, due to their tendency to early recurrence, is radiation therapy (3-6). Recently, electrochemotherapy (ECT) has been proposed as an alternative adjuvant therapy with promising results (7, 8). Case Report A 10-year-old castrated castrated domestic short hair cat was referred for a rapidly growing interscapular neoplasm. Accordingly to the owner, the mass grew in approximately 20 days. At presentation, the cat was quiet, alert and responsive, and had a 8 ×5×4 cm dorsal mass. A surgical biopsy was performed after the patient's sedation with a combination of medetodimine and ketamine as per manufacturers' instructions. Grossly, the neoplasm had a fibrous white cut surface with yellow flecks and foci of hemorrhage and necrosis with poorly defined borders. The sample was fixed in 10% formalin for histological analysis. Paraffin sections, 5 µm-thick, were prepared and stained with hematoxylin and