Treatment of corneal squamous cell carcinoma using topical 1% 5‐fluorouracil as monotherapy

Abstract

The purpose of this report is to discuss the use of topical 1% 5-fluorouracil as a sole therapy for canine corneal squamous cell carcinoma (SCC). A 12-year-old castrated male pug was evaluated for a well-demarcated, central, 3 mm in diameter, pale pink, raised, right corneal mass. An incisional biopsy was obtained using a #64 beaver blade after topical anesthesia and without sedation. A definitive diagnosis of corneal SCC was obtained after histopathologic evaluation of the biopsy. Topical 1% 5-fluorouracil ointment was applied to the right eye four times daily for 2 weeks followed by no treatment for 2 weeks, then treatment again twice daily for 2 weeks. The cornea remained free of recurrence 10 months after cessation of treatment. In dogs affected with corneal SCC, topical 1% 5-fluorouracil monotherapy may be a viable and cost-effective treatment option with minimal side effects. This chemotherapy agent may also have an effect on corneal pigmentation. Chronic cyclosporine therapy did not contribute to the pathogenesis of corneal SCC in the case described.

Highly invasive and poorly differentiated corneal squamous cell carcinoma in a dog

“…On the other hand, a potential association between the use of immunosuppressive drugs and corneal SCC has also been suggested [2, 5, 8]. Other factors involved in the development of this tumor include ultraviolet radiation exposure, chronic keratitis or superficial trauma [1, 4]. All of these features are present in our case, a French bulldog with chronic superficial keratitis and treatment with topical immunosuppressive therapy over a 5-year period.…”

“…Primary corneal neoplasia is rare in dogs, although a few cases of squamous cell carcinoma (SCC) have been already described [1–5].…”

“…In dogs, the tumor involves the superficial stroma or it colonize the corneal surface as an exophytic lesion [1, 3–5, 7–10]. However, in other species the tumor can be very infiltrative.…”

Clinical features and outcome of dermal squamous cell carcinoma in 193 dogs (1987‐2017)

“…A gold standard treatment approach has not been established for canine dermal SCC, however, some methods have been extrapolated from SCC in other locations and species. Reported treatment options for SCC have mainly centred on surgery, but there are also limited reports of photodynamic therapy, and medical therapies such as non‐steroidal anti‐inflammatories, retinoids and chemotherapy . Radiation therapy has been utilized for SCC arising in other locations, but has not been well described for dermal SCC in the dog…”

“…Reported treatment options for SCC have mainly centred on surgery, but there are also limited reports of photodynamic therapy, and medical therapies such as nonsteroidal anti-inflammatories, retinoids and chemotherapy. [29][30][31][32][33][34][35][36][37][38][39] Radiation therapy has been utilized for SCC arising in other locations, but has not been well described for dermal SCC in the dog. 40 Despite its relatively common occurrence, little has been published on the clinical features, behaviour or outcome of dogs with dermal SCC.…”