Page 446 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

424 PART IV Specific Malignancies in the Small Animal Patient

(IFN-γ), and granulocyte-macrophage colony-stimulating factor 0% to 17%, 15% to 19%, and 22% to 100%. 214,226 The lungs
(GM-CSF) followed by magnetofection before surgical resection are the most common site of metastasis, with other sites including
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regional lymph nodes, kidney, liver, spleen, intestines, and epi-
resulted in a 1-year local recurrence rate of 24%. In another phase
VetBooks.ir I trial by the same research group, two doses of intratumoral GM- dural and ocular infiltration. 214,215,225,226,232
CSF followed by magnetofection before surgical resection resulted in
a 1-year local recurrence rate of 50% and minimal treatment-related Survival
toxicities. Other immunotherapeutic agents such as IL-12 and ace- The overall prognosis for cats with ISSs is often very good despite
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mannan have been investigated with less favorable results. 256–258 their propensity for local tumor recurrence. The overall MST is
804 to 901 days to not reached for cats treated with wide surgical
Prognosis resection of 4-cm to 5-cm lateral margins and one to two fascial
layers for deep margins. 214,226,229 For cats treated with less aggres-
Local Recurrence sive surgery, the overall MST varies from greater than 395 days to
Local tumor control is the most challenging aspect of managing 608 days. 224,225,262 For cats treated with surgery and RT, regardless
cats with ISS. The best results are achieved after complete histo- of the timing of RT, the overall MSTs range from 520 to 1307
logic excision, and complete histologic excision is more likely after days with 1-, 2-, and 3-year survival rates of 62% to 86%, 42% to
aggressive surgical resection. The rate of complete histologic exci- 71%, and 28% to 68%, respectively. 213,232–236,260
sion is less than 50% when ISSs are excised with 2- to 3-cm lateral Prognostic factors associated with survival in cats with ISSs include
margins, 224,225 compared with 95% to 97% when excised with anemia, tumor size, treatment type, histologic subtype, mitotic rate,
4- to 5-cm lateral margins. 214,226 The local tumor recurrence rate local tumor recurrence, and metastatic disease. For cats treated with
is 14% to 22% after complete histologic excision compared with surgery and either preoperative or postoperative RT, anemia with
58% to 69% after incomplete excision. 214,229,243,259 Incomplete a packed cell volume (PCV) less than 25% was associated with
histologic excision of ISSs is associated with a 10-fold increased decreased ST. The MSTs for cats with a PCV less than and greater
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risk of local tumor recurrence. 259 Overall, the 1- and 2-year dis- than or equal to 25% were 308 days and 760 days, respectively, with
ease-free rates are 35% and 9%, respectively, after wide resection a 2-fold increased risk of tumor-related death for cats with a PCV less
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with 2- to 3-cm lateral margins, 224,225 compared with a 3-year than 25%. The 1- and 2-year survival rates for cats treated with a
disease-free rate of 86% after wide resection with 5-cm lateral PCV less than 25% were 40% and 24%, respectively, whereas the
margins or compartmental resections. 214,229 1- and 2-year survival rates for cats with a PCV greater than or equal
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When surgical resection is combined with either preoperative to 25% were 72% and 50%, respectively. Tumor size was associ-
or postoperative RT, the local recurrence rates are 28% to 45% ated with prognosis in two studies of cats treated with surgery alone.
with median DFIs of 13 to 37 months. 213,226,228,232–234,260 Simi- Cats with STSs smaller than 2 cm in diameter had an MST of 643
lar to surgical management of ISSs, complete histologic excision days, which was significantly longer than the MSTs of 558 days for
results in a significant improvement in time to local recurrence for cats with tumors 2 to 5 cm in diameter and 394 days for cats with
cats treated with surgery and RT, with a 700- to 986-day median STSs larger than 5 cm in diameter. In another study, cats with ISSs
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DFI for completely excised tumors and 112- to 292-day median greater than 3.75 cm had a significantly decreased ST. Although
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DFI for tumors resected with incomplete margins. 232,234 How- most studies do not show differences in outcomes between cats treated
ever, complete excision after preoperative RT does not appear to with surgery and either preoperative or postoperative RT, the outcome
improve local control rates because local tumor recurrence was was significantly worse for cats treated with preoperative RT (MST
reported in 42% of 59 cats with complete histologic excision and 310 days) than postoperative RT (MST 705 days) in one study, and
32% of 28 cats with incomplete histologic excision. 234 cats treated with preoperative RT had a 2-fold increased risk of tumor-
Prognostic factors for local recurrence include tumor size, surgi- related death. The 1- and 2-year survival rates for cats treated with
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cal dose or aggressiveness, completeness of histologic excision, and preoperative and postoperative RT were 42% and 29%, and 70% and
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histologic grade. In one study of 24 cats with ISSs, local recurrence 47%, respectively. In another study of 52 cats treated with surgery
was significantly more likely after wide resection of larger tumors; alone, including eight cats with presumed ISSs, histologic subtype
and for each unit increase in tumor size, cats were two times more was prognostic with MSTs for cats with FSA (640 days) and PNST
likely to develop local recurrence and two times more likely to have a (645 days) significantly better than for cats with MFH (290 days).
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tumor-related death. 261 A number of studies have shown the impor- Survival was significantly associated with mitotic rate in one study
tance of an aggressive surgical approach in the management of cats of 24 cats with a 994-day MST for cats with mitotic count greater
with ISSs, but this most likely is related to the ability to achieve than 20 mitoses per 10 HPFs compared with an MST that was not
complete histologic excision rather than the surgical approach spe- reached in cats with a mitotic rate less than or equal to 20 mitoses per
cifically. The median time to first recurrence after marginal resection 10 HPFs. The MST for cats with local tumor recurrence was 327
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is 79 days compared with 325 to 419 days for wide resection or to 499 days compared with 1098 to 1461 days to not reached for
radical surgery. 225 In addition, the median time to first recurrence cats without local tumor recurrence. 214,226,261 The estimated 2-year
is only 66 days when the first surgery is performed at a nonreferral survival rates for cats without and with local recurrence are 75% and
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institution compared with 274 days at referral institutions. 224,225 In 37%, respectively. The MST for cats without distant metastasis was
another study of 57 cats with wide resection of ISSs, the local recur- 929 to 1528 days compared with 165 to 388 days for the 20% to
rence rate was 39% and significantly more likely with grade III ISSs 21% of cats that developed distant metastasis. 214,226 Distant metasta-
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compared with either grade I or II ISSs. 226 sis increased the risk of tumor-related death by three times.
Metastasis
Metastasis is relatively uncommon in cats with ISSs. The meta- Prevention
static rate varies from 0% to 24%. 209,213–215,225,226,232,234,261,262 The recommendations on preventing ISSs in cats are controver-
Metastasis is significantly more likely in cats with grade III ISSs 226 ; sial. These include changing the sites of vaccine administration,
and the metastatic rates for cats with grade I, II, and III ISSs are decreasing the use of polyvalent vaccines, using nonadjuvanted