Veterinary Surgical Oncology

In a study of 76 cats with vaccine‐associated sarcomas, 26 cats were treated with chemotherapy in addition to surgery and radiotherapy. Neither recurrence rates, rate of metastasis, nor survival times were improved in the chemotherapy group (Cohen et al. 2001). Neoadjuvant and adjuvant chemotherapy with epirubicin (25 mg/m 2) combined with anatomical resection of FISAS resulted in local tumor recurrence in 3 cats (14%) at days 264, 664, and 1573 after surgery (Bray and Polton 2016), according to the authors these results demonstrate superior rates of tumor‐free survival and disease‐free interval when compared to historical controls.

Of 11 cats treated by stereotactic radiation for FISAS, 8 responded. The median DFI was 242 days, and an MST of 301 days (Nolan et al. 2013).

No significant effect of chemotherapy only in the treatment of FISAS in clinical settings has been reported yet, although the high metastatic rate is an indication for systemic treatment (Bregazzi et al. 2001; Cohen et al. 2001). Possibly the tyrosine kinase inhibitor, imatinib, will have an effect on FISAS. It inhibited the growth of FISAS in a murine xenograft model (Katayama et al. 2004) and could affect FISAS due to the presence of platelet derived growth factor receptor which is a receptor tyrosine kinase. In one phase 1 clinical trial of imatinib, 4/9 cases trialed had FISAS. In these four cases, a response to treatment was noted and consisted predominantly of short‐term tumor stabilization (Lachowicz et al. 2005).

In vitro doxorubicin and etoposide alone and in combination differentially alter FISAS cell viability and cycle (Hill et al. 2014).

Although masitinib did not directly enhance FISAS cell radiosensitivity under normal in vitro conditions (Turek et al. 2014), combined chemo/radiation therapy has been reported to result in a significant reduction in tumor growth compared to the respective mono‐therapies with either doxorubicin or radiation. These results support the use of the concomitant chemo/radiation therapy for adjuvant treatment of FISS, particularly in advanced or recurrent disease where surgery alone is no longer feasible (Petznek et al. 2014).

Immunotherapy has been reported successful in xenogeneic cells secreting human interleukin‐2 (IL‐2). Totally, 16 cats with FISAS were treated, two of which had local recurrence and three had metastatic disease. MST was 16 months in IL‐2 treated cats vs. 8 months for nontreated cats (Quintin‐Colonna et al. 1996).

A second study conducted with human and feline IL‐2 resulted in a lower tumor recurrence rate compared to control cats not receiving immunotherapy after surgery and iridium‐based radiotherapy (39% and 28% vs. 61% for the controls) (Jourdier et al. 2003).

Despite the recommendation for vaccine administration to be on the distal aspect of a limb to facilitate the attainment of clean surgical margins via limb amputation, a high proportion of tumors still developed in the interscapular region in a recent study evaluating the demographics of VAS. For prevention, administration of any irritating substance should be avoided. Vaccination should be performed as often as necessary, but as infrequently as possible. Nonadjuvanted, modified‐live, or recombinant vaccines should be selected in preference to adjuvanted vaccines. Injections should be given at sites at which surgery would likely lead to a complete cure; the interscapular region should generally be avoided. Postvaccination monitoring should be performed (Hartmann et al. 2015; Shaw et al. 2009). However, these current feline vaccine site recommendations may not be appropriate for cat owners as was concluded by Carwardine et al. (2014) based on an anonymous internet‐based cross‐sectional study in the UK wherein cat owning respondents would not allow amputation of their cats’ forelimb (20%), hindlimb (15%), or tail (15%).

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