Treatment choices for oral cancer in cats. What is possible? What is reasonable?

Combining radiation therapy with zoledronate for the treatment of osteo-invasive feline oral squamous cell carcinoma

Feline oral squamous cell carcinoma (FOSCC) is the most common oral tumour diagnosed in pet cats and carries a poor prognosis with <10% one-year survival despite multi-modal therapies. Tumours of the mandible or maxilla are frequently osteo-invasive and pain can result from osteolysis. Zoledronate is a bisphosphonate that inhibits osteoclasts and reduces bone resorption. Radiation therapy (RT) is used to treat FOSCC due to anti-cancer activity and ability to improve quality of life. We hypothesized RT can be safely combined with zoledronate, and that this combinatory therapy would be efficacious, well tolerated, and result in decreased bone resorption in cats with FOSCC. SCCF1 cell line was treated with zoledronate before, concurrently, or after RT, and clonogenic assays were performed to determine if an optimal dosing schedule would be identified. Nine cats with osteoinvasive FOSCC were recruited for treatment with 4 weekly doses of 8 Gy RT combined with zoledronate administered at the first and fourth treatments. Serial CT scans were performed to assess tumour response. Safety and tolerability were monitored with hematologic and biochemical parameters, and acute radiation effects were characterized. Serum c-telopeptide (CTx) and relative bone mineral density (rBMD) by dual -energy X-ray absorptiometry (DEXA) quantified bone resorption. In vitro studies showed no clear benefit to timing of zoledronate with RT, therefore all zoledronate was administered concurrently with RT in FOSCC patients. Based on tumour volume, 4/9 (44.4%) cats achieved partial remission, 4/9 (44.4%) stable disease and 1/9 (11.1%) had progressive disease. The combinatory therapy was well-tolerated based on biochemical measurements, and all patients experienced decreased serum CTx. Combining RT with zoledronate in tumour-bearing cats is safe, well-tolerated, results in a partial remission rate of up to 44%, and decreases serum CTx, a marker of bone resorption.

Utilizing feline oral squamous cell carcinoma patients to develop NQO1-targeted therapy

Developing effective therapies for the treatment of advanced head-and-neck squamous cell carcinoma (HNSCC) remains a major challenge, and there is a limited landscape of effective targeted therapies on the horizon. NAD(P)H:quinone oxidoreductase 1 (NQO1) is a 2-electron reductase that is overexpressed in HNSCC and presents as a promising target for the treatment of HNSCC. Current NQO1-targeted drugs are hindered by their poor oxidative tolerability in human patients, underscoring a need for better preclinical screening for oxidative toxicities for NQO1-bioactivated small molecules. Herein, we describe our work to include felines and feline oral squamous cell carcinoma (FOSCC) patients in the preclinical assessment process to prioritize lead compounds with increased tolerability and efficacy prior to full human translation. Specifically, our data demonstrate that IB-DNQ, an NQO1-targeted small molecule, is well-tolerated in FOSCC patients and shows promising initial efficacy against FOSCC tumors in proof-of-concept single agent and radiotherapy combination cohorts. Furthermore, FOSCC tumors are amenable to evaluating a variety of target-inducible couplet hypotheses, evidenced herein with modulation of NQO1 levels with palliative radiotherapy. The use of felines and their naturally-occurring tumors provide an intriguing, often underutilized tool for preclinical drug development for NQO1-targeted approaches and has broader applications for the evaluation of other anticancer strategies.

Outcomes of eight cats with oral neoplasia treated with radical mandibulectomy

OBJECTIVE

To report outcomes after radical mandibulectomy in cats.

STUDY DESIGN

Multi-institutional retrospective study.

ANIMALS

Eight cats were included.

METHODS

Medical records were searched for cats with confirmed oral neoplasia treated with radical mandibulectomy. Data collected included demographics, surgical procedure, histopathological diagnosis, postoperative management, and outcomes.

RESULTS

Ages ranged from 8 to 17 years. All cats had 75% to 90% of the mandible removed and feeding tubes placed. Seven cats had squamous cell carcinoma, and one cat had a giant cell tumor. Six cats ate on their own postoperatively. Three cats had local recurrence and tumor-related died at 136 and 291 days. Six cats had no recurrence, with survival times of 156, 465, 608, and 1023 days, and two cats were still alive at 316 and 461 days after surgery. The three long-term survivors died of causes unrelated to oral neoplasia. One cat died at 156 days due to aspiration of food material. The overall estimated mean survival time was 712 days.

CONCLUSION

After radical mandibulectomy, independent food intake was achieved in 6 of eight cats, and four cats lived longer than one year.

CLINICAL SIGNIFICANCE

Radical mandibulectomy should be considered for the treatment of extensive oral neoplasia in cats. Successful long-term outcomes are possible with aggressive supportive care perioperatively.

MANDIBULAR SQUAMOUS CELL CARCINOMA IN A BOBCAT (LYNX RUFUS)

A 23-yr-old female spayed bobcat (Lynx rufus) presented with a 1-wk history of hypersalivation. On examination, the right mandible was markedly thickened, the right mandibular dental arcade was missing, and the oral mucosa over the right mandible was ulcerated and thickened. Skull radiographs and fine needle aspirate cytology were supportive of squamous cell carcinoma. The bobcat was euthanized as a result of its poor prognosis. Necropsy confirmed a diagnosis of oral squamous cell carcinoma of the mandible. To the authors' knowledge, this is the first report of oral squamous cell carcinoma in a bobcat.

Cutaneous squamous cell carcinoma in the cat: current understanding and treatment approaches

PRACTICAL RELEVANCE

Squamous cell carcinoma (SCC) is a tumour that commonly involves the skin or oral cavity and is, therefore, an important differential diagnosis for any cutaneous lesion(s), especially any non-healing scabbing lesions on the eyelids, nasal planum or ears of light-coloured cats.

CLINICAL CHALLENGES

Superficial lesions of the nasal planum, discrete small eyelid lesions and lesions on the tips of pinnae are relatively easily treated, but higher stage lesions are more challenging to manage and may compromise the cosmetic appearance of the cat.

AUDIENCE

This review article is aimed at all veterinary practitioners that see cats.

EVIDENCE BASE

The review summarises the peer-reviewed literature relating to our understanding of feline cutaneous SCC. Unfortunately, the literature is limited and in need of updating in areas.