Page 481 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 23 Cancer of the Gastrointestinal Tract 459

adjacent normal hepatic tissue, has been described in 6 dogs
1 with nonresectable HCC. 427 In this study, 3-D conformal
RT was delivered at 6 to 10 Gy per fraction to a total dose of 18
VetBooks.ir 0.8 to 42 Gy with 1 to 2 fractions per week for a total of 3 to 7 frac-
Survival (proportion) 0.6 the six dogs, and an MST of 567 days. 427 356,370 The poor response
tions.
427
This RT protocol resulted in partial responses in five of
HCC is considered chemoresistant in humans because
response rates are usually less than 20%.
0.4
ment of drug resistance due to either the role of hepatocytes in
0.2 to systemic chemotherapy is probably a result of rapid develop-
detoxification or expression of P-glycoprotein, a cell membrane
efflux pump associated with multidrug resistance. 356 However,
0 single-agent gemcitabine has been investigated in dogs with
0 250 500 750 1000 1250 1500 1750 unresectable HCC with encouraging results. 428 In one this
Survival (d) study, 18 dogs with mostly nodular and diffuse well-differenti-
Surgery ated HCCs were treated with gemcitabine for 5 weeks. 428 The
No surgery overall MST was 983 days, but depended on the morphology
and resectability of the tumor. 428 The MSTs were 1339 days
• Fig. 23.23 Kaplan–Meier survival curve for dogs with massive hepatocel-
lular carcinoma. The median survival time for dogs with surgically resected for dogs with massive HCC, 983 days for dogs with nodular
tumors is significantly better than dogs not treated with curative-intent liver HCC, and 113 days for dogs with diffuse HCC; and the MSTs
lobectomy. (Reprinted with permission from Liptak JM, Dernell WS, Mon- were 1339 days for dogs with incompletely excised HCC, which
net E, et al. Massive hepatocellular carcinoma in dogs: 48 cases (1992– included all four dogs with massive HCC and 9 of 10 dogs with
2002). J Am Vet Med Assoc. 2004;225:1225–1230.) nodular HCC, and 197 days for dogs with nonresectable HCC,
including all four dogs with diffuse HCC. 428 Novel treatment
options currently being investigated in human medicine include
survival. 419 Metastasis to other regions of the liver and lungs immunotherapy, hormonal therapy with tamoxifen, and antian-
has been documented in 0% to 37% of dogs, but metastasis is giogenic agents. 370
rare in recent clinical reports and most deaths are unrelated to
HCC. 357,362,363,419 The MST for dogs with massive HCC after Bile Duct Tumors
liver lobectomy are greater than 1460 to 1836 days, 363,419 and
the MST was 2.4 years for six cats with HCC treated with liver Bile duct adenomas can present as either single (e.g., massive) or
lobectomy. 373 In comparison, the MST of 270 days was signifi- multifocal lesions. Liver lobectomy is recommended for cats with
cantly decreased for six dogs managed conservatively, and these single bile duct adenoma (cystadenoma) or multifocal lesions con-
dogs were 15.4 times more likely to die of tumor-related causes fined to one to two lobes. 358–360,374–376 The prognosis is very good
than dogs treated surgically. 363 Prognostic factors in dogs with after surgical resection with resolution of clinical signs and no
massive HCC include surgical treatment, side of liver involve- reports of local recurrence or malignant transformation. 360,374,375
ment, ALT and AST activity, ratios of ALP-to-AST and ALT-to- Liver lobectomy is also recommended for cats and dogs with
AST, and completeness of histologic excision. 363,419 Right-sided massive bile duct carcinoma. However, survival time has been
liver tumors, involving either the right lateral lobe or caudate poor in cats and dogs treated with liver lobectomy because the
process of the caudate lobe, had a poorer prognosis because majority have died within 6 months as a result of local recurrence
intraoperative death was more likely due to caudal vena cava and metastatic disease. 360,429 There is no known effective treat-
trauma during surgical dissection. 363 There was no difference ment for cats and dogs with nodular or diffuse bile duct carcino-
in survival time if dogs with right-sided massive HCC survived mas because these lesions are not amenable to surgical resection
surgery. 363 Increased ALT and AST were associated with a poor and other treatments are often not successful.
prognosis in one study, which may reflect more severe hepatocel-
lular injury secondary to either large tumor size or more aggres- Neuroendocrine Tumors
sive biologic behavior. 363
In contrast, the prognosis for dogs with nodular and diffuse Carcinoids have an aggressive biologic behavior and are usually
HCC is poor. Surgical resection is usually not possible because of not amenable to surgical resection because solitary lesions and
involvement of multiple liver lobes. Treatment options for nodular massive morphology are rare. 357,366 The efficacy of RT and che-
and diffuse HCC in humans include liver transplantation or mini- motherapy is unknown. Prognosis is poor because metastasis to
mally invasive procedures for regional control, such as ablation the regional LNs, peritoneum, and lungs occurs in 93% of dogs
or embolization. 370 Bland embolization and chemoembolization and usually early in the course of disease. 357,366
have been reported with moderate success in the palliation of four
dogs and one cat with HCC, 423–425 and microwave ablation has Sarcomas
been described in five dogs with diffuse hepatic neoplasia, includ-
ing one dog with HCC. 426 The role of RT and chemotherapy in Liver lobectomy can be attempted for solitary and massive sarco-
the management of HCC is largely unknown. mas. However, the prognosis is poor because metastatic disease
Traditional RT is ineffective in the management of liver tumors, is often present at the time of surgery. 357,380 Chemotherapy has
as the canine liver cannot tolerate cumulative doses greater than not been investigated in the treatment of primary hepatic sarco-
30 Gy 356,370 ; however, three-dimensional (3-D) conformal RT, mas, although, similar to other solid sarcomas, response rates are
which enables targeted high-dose RT to the tumor while sparing likely to be poor. Doxorubicin-based protocols and ifosfamide