Gemcitabine as a radiosensitizer for nonresectable feline oral squamous cell carcinoma

Gemcitabine as a Radiosensitizer for Nonresectable Feline Oral Squamous Cell Carcinoma Eight cats with locally advanced, oral squamous cell carcinoma (SCC) were treated with a combination of gemcitabine and palliative radiotherapy. Low-dose gemcitabine was administered twice weekly (25 mg/m2) in conjunction with megavoltage radiation in 6 Gray (Gy) fractions for a total dose of 36 Gy. Responses included two complete and four partial responses, and two cats had no response to therapy. Median duration of remission was 42.5 days (range, 11 to 85 days). Median survival time was 111.5 days (range, 11 to 234 days). This data suggests that a combination of low-dose gemcitabine and palliative radiation therapy may be tolerable for cats with oral SCC and may cause a therapeutic benefit. J Am Anim Hosp Assoc 2003;39:463–467.

Pamela D. Jones, DVM Louis-Philippe de Lorimier, DVM Barbara E. Kitchell, DVM, PhD, Diplomate ACVIM (Internal Medicine, Oncology) John M. Losonsky, DVM, MS, Diplomate ACVR

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From the Department of Veterinary Clinical Medicine, Veterinary Teaching Hospital, University of Illinois, 1008 West Hazelwood Drive, Urbana, Illinois 61802. JOURNAL of the American Animal Hospital Association

Introduction Squamous cell carcinoma (SCC) is the most common malignant oral neoplasm in cats.1-3 A retrospective review of 371 cats with oral neoplasms found that over the 10-year period of the survey, oral neoplasia accounted for 10% of all feline neoplasms diagnosed. Of this 10%, the majority (61.2%) were SCC.4 The most common site was in the sublingual region.3,4 Death due to distant metastasis is rare, and the majority of patients die because of progressive local disease and local treatment failure.5 The prognosis for feline oral SCC is guarded, and the best potential for cure is provided by complete surgical excision. Oral SCC is often detected late in the disease course and is therefore not amenable to surgical resection. Unfortunately, nonresectable feline oral SCC responds poorly to traditional therapies such as chemotherapy and radiation therapy.1-3 Multimodality therapy has been reported to result in the longest survival times for patients with incompletely resected tumors. Longer survival times have been achieved with aggressive surgical excision and radiation with curative intent. One study of seven cats treated with mandibulectomy and radiotherapy reported a median survival time of 14 months (420 days).6 Numerous chemotherapy agents have been used in the attempt to improve survival in these patients. These agents have been used alone and in combination with radiotherapy. A highly effective agent used in the treatment of head and neck SCC in humans, a liposomal cisplatin analogue (L-NDDP), was found to be ineffective for the treatment of feline oral SCC in a recent phase I/II study.7 One study evaluated the hypoxic cell sensitizer etanidazole (ETA) injected intratumorally in combination with radiotherapy. This study of 11 cats revealed a partial response rate of 100%, with an overall median survival time of 116 days.8 The use of mitoxantrone in combination with radiotherapy has been investigated as well. In one study, seven cats had median tumor control of 138 days and median survival time of 180 days.9 Another study evaluating the combination of mitoxantrone and radiotherapy supported 463

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these early findings, with a complete response rate of 72.7% (in 8/11 cats) and a median remission duration of 170 days.10 However, both of the previously mentioned mitoxantrone studies combined full-course fractionated radiotherapy. Overall, median survival times for cats with oral SCC vary between 2 and 10 months, with