Palliative Radiation Therapy Outcomes for Cats With Oral Squamous Cell Carcinoma (1999–2005)

Abstract

Squamous cell carcinoma (SCC) accounts for approximately 10% of all feline tumors. The purpose of this retrospective study was to describe outcomes for a group of cats with oral SCC that were treated with palliative radiation therapy. Fifty-four cats met the inclusion criteria of nonresectable, oral SCC treated with coarse fractionated megavoltage (MeV) radiation therapy. Radiation therapy for all cats was delivered with a 6 MeV linear accelerator. Total radiation doses of 24 Gray to 40 Gray were administered in three to four fractions, once-per-week over 4 to 5 weeks. Concurrent chemotherapy protocols varied and were administered at the discretion of the clinician and client. Forty-nine patients completed the planned treatment protocols. Overall mean and median survival times for cats completing the planned treatment protocols were 127 and 92 days (n = 49). Mean and median survival times of cats receiving palliative radiation therapy alone were 157 and 113 days (n = 12). Mean and median survival times of patients receiving both radiation therapy and chemotherapy were 116 and 80 days (n = 37). Patients with sublingual tumors had a median survival time of 135 days (n = 15), compared to mandibular tumors that had a median survival time of 80 days (n = 26). For the majority of patients that completed the planned treatment protocol (65%), owners reported a subjectively improved quality of life. Findings from this uncontrolled study supported the use of palliative radiation therapy for cats with nonresectable oral squamous cell carcinoma.

Intratumoral injection of radioactive holmium (166Ho) microspheres for treatment of oral squamous cell carcinoma in cats

“…In a large study of 54 animals, only 3 (6%) animals had a complete response, 30 (61%) had a partial response and 16 (33%) had stable disease at completion of treatment. The majority (49/54 animals, 91%) experienced complications compared with only 1 of 11 (9%) in the present 166 Ho microbrachytherapy study . The median OS in these studies was 60, 92 and 111.5 days with a median local progression free survival of 43 days, respectively …”

“…The outcome in this study compares favourably with currently available treatments for FOSCC with or without bone involvement in respect of clinical efficacy and complications: Several external beam palliative radiation schemes have been used in cats with 3 to 6 fractions of 6 to 10 Gy with only limited effect . Radiation side effects were severe, resulting in a significantly diminished quality of life and early treatment termination: 43% of the patients did not complete the radiation protocol in 1 study .…”

“…Surgery is only considered in a very select group of cats with small, localized tumours. Effectiveness of palliative radiation protocols (consisting of 3‐6 sessions of 6‐10 Gy) and stereotactic radiation is low in felines with response rates of 39% or less and median overall survival (OS) times of 60 to 106 days . More recently, several case series of accelerated hypofractionated radiotherapy protocols with or without chemotherapy and/or surgery suggest improved survival outcomes of 86 to 163 days .…”

“…More recently, several case series of accelerated hypofractionated radiotherapy protocols with or without chemotherapy and/or surgery suggest improved survival outcomes of 86 to 163 days . However, these are intensive treatment protocols that require multiple anaesthetic interventions and are accompanied by considerable costs and therapy‐induced morbidity, with 91% overall complication rate and up to 78% grade 3 oral mucositis . Chemotherapy, tyrosine kinase inhibitors and immunotherapy alone have not achieved durable responses in macroscopic FOSCC …”

Treatment of advanced canine anal sac adenocarcinoma with hypofractionated radiation therapy: 77 cases (1999–2013)

“…In veterinary medicine, this often includes advanced disease states with the goal of treating or delaying onset of a clinical symptom, in which case treatment intent is often somewhere between a purely palliative and a definitive philosophy . The majority of reports assessing the role of palliative radiation in veterinary medicine have focused on osteosarcoma, nasal carcinoma and melanoma . While treatment protocols used in this setting vary considerably between institutions and tumour type, clinical benefits have been reported including relief of tumour‐related pain or bleeding and in some instances a decrease in the size of the primary tumour leading to improved survival times .…”