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· FISS: The combination of surgery and radiation therapy is generally accepted to be the most effective treatment. However, for tumours excised with radical surgery with wide histologic margins, adjuvant radiation may not be necessary. A recombinant canarypox virus expressing feline Il-2 (Oncept IL-2) improved tumour control in cats treated with surgery and radiation therapy in one study (4). The addition of chemotherapy (doxorubicin or epirubicin) may improve outcomes, but the true benefit is not clear.
Options for non-resectable tumours
· Canine STS
S. Ryan1, C. Cannon1
1The University of Melbourne, UVet Hospital, Werribee, Australia
Stewart Ryan BVSc (hons) MS DACVS MANZCVS University of Melbourne U-Vet Animal Hospital
Learning objective: Develop an approach to diagnosis of suspected soft tissue sarcomas in dogs and cats, including interpretation of histopathology reports. Understand the different possible surgical approaches, appropriate staging tests and indications for adjunctive treatments.
Soft tissue sarcoma (STS) is a generic term, encompassing a number of different mesenchymal tumour types. Generally, this term encompasses fibrosarcoma, peripheral nerve sheath tumour, myxosarcoma, perivascular wall tumour and liposarcoma. Tumours which are specifically excluded because they have different presentations and/or behaviour are muscle origin sarcomas, synovial sarcomas, haemangiosarcoma and lymphangiosarcoma.
Feline injection site sarcomas (FISS) are a specific subtype of soft tissue sarcoma characterised by history and location (growth at a site of previous injection), aggressive histologic features and often associated inflammation. Non-injection site related STS in cats should be managed as for canine STS, though evidence for prognostic factors such as grade and mitotic index is lacking.
Diagnosis for all soft tissue sarcomas typically requires histopathology. Cytology may be diagnostic or at
least suggestive, but especially for well-differentiated sarcomas, cannot reliably distinguish between neoplastic and reactive mesenchymal tissue. Cytology is recommended as a first step to rule out other possibilities e.g. mast cell tumour. Histopathology
may be obtained by incisional or excisional biopsy. In general, unless excision is achievable with wide margins, incisional biopsy for suspected soft tissue sarcomas should be performed to confirm the diagnosis and
grade to plan the most appropriate surgery. Revision surgeries for incomplete margins following excisional biopsy are typically more extensive than what would have been required had an appropriate first surgery been performed. For suspected FISS, referral should always be recommended, as radical excision is typically required and outcomes are improved if the first surgery is aggressive. Incisional biopsy should be considered
· Chemotherapy: Doxorubicin in macroscopic STS is associated with an overall response rate of 20-30%. Mitoxantrone and ifosfamide may be effective in some dogs. Metronomic chemotherapy with chlorambucil may shrink STS or maintain stable disease in some dogs (6)
· Palliative RT is often effective at shrinking FISS in the short term, though there is often progression within a few months. Adding chemotherapy (doxorubicin) may improve response rates and duration. Doxorubicin alone will also be effective in some cases, with response rates of 40-50%, though again these do
not tend to be durable. Metronomic chemotherapy has not been. IL-2 vaccine may slow progression in unresectable feline STS (unclear if FISS were included in this abstract) (7).
Dennis MM, McSporran KD, Bacon NJ, Schulman FY, Foster RA, Powers BE. Prognostic factors for cutaneous and subcutaneous soft tissue sarcomas in dogs. Vet Pathol 2011; 48:73-84
McSporran KD Histologic grade predicts recurrence for marginally excised ca- nine subcutaneous soft tissue sarcomas. Vet Pathol 2009;46:928-33
Elmslie RE, Glawe P, Dow SW. Metronomic therapy with cyclophosphamide and piroxicam effectively delays tumor recurrence in dogs with incompletely resected soft tissue sarcomas J Vet Intern Med 2008;22:1373-1379
Jas D, Soyer C, de Fornel-Thibaud P, Oberli F, Vernes D, Guigal P-M, Poulet H, Devachelle P Adjuvant immunotherapy of feline injection-site sarcomas with the recombinant canarypox virus expressing feline interleukine-2 evaluated in a controlled monocentric clinical trial when used in association with surgery and brachytherapy Trials in Vaccinol 2015;4:1-8
Cancedda S, Marconato L, Meier V, Laganga P, Roos M, Leone VF, Rossi F, Rohrer Bley C Hypofractionated radiotherapy for macroscopic canine soft tissue sarcoma: A retrospective study of 50 cases treated with a 5x6 Gy protocol with or without metronomic chemotherapy Vet Radiol Ultrasound 2016;57:75-83
Leach TN, Childress MO, Greene SN, Mohamed AS, Moore GE, Schrempp DR, Lahrman SR, Knapp DW. Prospective trial of metronomic chlorambucil chemother- apy in dogs with naturally occurring cancer Vet Comp Oncol 2012;10:102-12 Athanasiadi I, Kaser-Hotz B, Buchholz J, Ruess-Melzer K, Herzog A. Combination of Palliative Radiation Therapy and Local Application of Oncept IL-2 (Merial) for the Treatment of Feline Soft Tissue Sarcoma (STS). Proceedings of the Veterinary Cancer Society 2016; October 20-22; Orlando FL
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  · Radiation therapy (RT) can be used with a definitive or palliative intent. With definitive type protocols, control rates are approximately 50% at 1 year and 33% at 2 years. Generally, radiation is used in macroscopic STS with a palliative intent, and approximately
50% respond with a median time to progression of approximately 5-10 months. One study in dogs treated with palliative RT +/- metronomic chemotherapy
found that the addition of metronomic chemotherapy improved survival time but not progression free interval, so the true impact is hard to determine (5)

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