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for untreated dogs. Another study evaluated low‐dose radiation therapy. Chemotherapy, however, may have
VetBooks.ir cyclophosphamide and its effects on T‐regulatory cells beneficial effects on local tumor control. The effect of
doxorubicin alone was evaluated in 12 nonresectable
and tumor angiogenesis in dogs with STS. This study
2
found that dogs receiving 15 mg/m /day of cyclophos-
>50% in tumor volume was seen in 50% of the animals.
phamide had significant decreases in the number and vaccine‐associated sarcomas. An initial reduction of
percent of T‐regulatory cells as well as microvessel den- Unfortunately, the response was not durable, and all cats
sity, further supporting that metronomic therapy may showed progressive disease. However, the median over-
provide antitumor effects. all survival was significantly longer for cats that did
respond. More recently, tyrosine kinase inhibitors have
been shown to block the PDGF/PDGF receptor signaling
Cats
pathway in vaccine‐associated cell lines and to inhibit
Surgery and Radiation Therapy vaccine‐associated growth in a murine model. These
Injection‐associated sarcomas are poorly encapsulated drugs are currently being evaluated for treatment of
tumors with extension and infiltration along fascial these tumors.
planes. Surgically, 3 cm margins laterally and one fascial
plane deep to tumor have been utilized for the treatment
of vaccine‐associated sarcoma. However, this is not Prognosis
adequate considering the reported high rates of local
recurrence which range from 35% to 59%. In response to Dogs
this, surgical margins of >3 cm laterally and two fascial
planes deep to the tumor, along with partial scapulec- The overall prognosis for dogs with STS is good, but the
tomy, osteotomy of spinous processes or hemipelvec- range of biologic behavior for these tumors can be broad.
tomy when indicated, are now recommended. Despite The median survival time for dogs ranges from 3.9 years
attempting aggressive surgical margins, complete following surgery alone to 6.2 years with surgery and
resection is achieved in less than 50% of cats, and overall adjunctive radiation. Overall, up to 33% of dogs eventu-
one‐ and two‐year disease‐free intervals are only 35% ally die of tumor‐related causes.
and 9%. A retrospective study evaluated radical excision Research has identified valuable prognostic informa-
for treatment of 91 STSs. Radical excision was defined as tion including histologic grade, mitotic index, and com-
5 cm of tissue beyond the palpable edges of the tumor pleteness of surgical margins. A complete histologic
and two fascial planes or bone deep to the tumor. With margin predicts nonrecurrence and recurrence appears
this approach, surgery resulted in complete margins in to increase with grade. The metastatic rate for dogs with
97% of cases and a local recurrence rate of 14%. grade I or grade II is less than 15% compared to 41% for
Due to the high rate of local recurrence following wide grade III STS. High mitotic index (>9 mitotic figures per
surgical resection, full‐course radiation is considered 10 high‐power fields) is prognostic for recurrence,
essential in the management of cats with vaccine‐associ- metastais, and survival. Other factors, including markers
ated sarcomas. The timing of the radiation therapy is of cellular proliferation, tumor dimension, tumor loca-
controversial, and there are pros and cons to preopera- tion, histologic type, invasiveness, and cytogenetic pro-
tive versus postoperative approaches. The time to recur- file, may be useful indicators of prognosis but presently
rence when the combination of surgery and radiation require further investigation.
therapy is used ranges from 13.5 months to 19.5 months.
In studies investigating preoperative radiation therapy, Cats
complete resection significantly improved time to local
recurrence with a disease‐free interval for completely The prognosis for vaccine‐associated sarcomas treated
excised tumors of 33 months versus 10 months for with surgery alone, using traditional recommendations
incompletely excised tumors. Unfortunately, even with of 3 cm margins and one fascial plane deep to the tumor
combination therapy, recurrence rates still range from bed, is poor. Multimodal treatment (extensive surgery,
40% to 45%. radiotherapy, chemotherapy) is recommended and the
use of sophisticated imaging techniques can improve
Chemotherapy diagnosis and help in surgical planning. The combina-
The most common chemotherapy drugs used to treat tion of radiation therapy either pre‐ or postoperatively
vaccine‐associated sarcomas are doxorubicin, carbopl- has improved the disease‐free interval and overall sur-
atin, and cyclophosphamide. Postoperative chemother- vival time in cats with vaccine‐associated sarcomas.
apy has been shown to have only a minimal effect on Median survival time with combination therapy is
survival in cats treated with curative‐intent surgery and 23 months compared to 19 months with surgery alone.