Page 199 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

178 PART III Therapeutic Modalities for the Cancer Patient

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A B

• Fig. 11.2 Fluoroscopic images preembolization (A) and postembolization (B) of a liver tumor in an 11-year-
old male castrated mixed breed dog. Note the outline of the tumor marked by the dashes (A), and the lack
of tumor opacification postembolization (B).

Traditional chemoembolization involves the administration embolization in dogs with large hepatic masses, one dog was treated
of a slurry containing a contrast medium, embolic agent, and with bland embolization and one dog was treated with chemoem-
a chemotherapy agent. Many chemotherapy agents have been bolization. Clinical improvement was noted in the dog treated
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described in humans including doxorubicin, epirubicin, cispla- with bland embolization, but the dog died at home approximately 4
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tin, and mitomycin C. 33,36 Much research is being invested into months posttreatment. Doxorubicin was administered with poly-
the evaluation of other means of delivering chemotherapy to vinyl alcohol particles and lipiodol in the dog treated with chemo-
tumors in combination with embolization. Drug-eluting beads embolization; however, the dog died approximately 3 weeks after
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(DEBs) have now been evaluated in several human studies and treatment as a consequence of an unrelated traumatic event. In
have demonstrated some promise. 33,37 These beads are generally another study, superselective catheterization of the hepatic arterial
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made of a biocompatible polymer that can bind chemothera- branch was not achieved in two dogs. Both dogs underwent trans-
peutic agents. 35,37 The drug can be released in the tumoral blood arterial chemotherapy and lipiodol administration, and one dog also
supply in a controlled and sustained manner; consequently, the received an additional embolic agent. When hepatic tumor size was
chance of systemic side effects from the chemotherapy may be evaluated after treatment, both dogs demonstrated stable disease
decreased. Further evaluation of the efficacy of DEBs com- at 1 month, but progressive disease at 3 months after treatment.
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pared with traditional transarterial chemoembolization needs A hepatocellular carcinoma in a cat treated with bland emboliza-
to be performed to determine whether there is a benefit of one tion has also been reported. In this cat, CT revealed a decrease in
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delivery agent over the other. 33 tumor size at 71 days posttreatment. Surgical resection was pursued
An additional agent, called lipiodol, is also often used during 231 days after embolization and no recurrence was noted at 481
chemoembolization. Lipiodol is an iodinated poppy seed lipid– days after tumor removal. 42
based medium that has several proposed benefits: (1) it is radi- Prostatic artery embolization (PAE) is a growing field in both
opaque and can be used in the slurry to replace contrast medium, human and veterinary medicine. In humans, PAE has been used
(2) it acts as an embolic agent on its own, and (3) it preferentially mostly as a treatment for benign prostatic hyperplasia (BPH)
concentrates in tumor tissue longer than in nontumor tissue. 35,38 or to treat prostate-induced hematuria. Experimentally, dogs
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Most descriptions of liver chemoembolization include lipiodol in have undergone PAE in a model of BPH. In this study, four of
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the injected embolic slurry. seven dogs with induced BPH had reduction of prostate size after
The superiority of embolization and chemoembolization to embolization. The use of PAE to treat prostatic neoplasia has
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each other remains controversial. 34,35 Embolization (also called also recently been reported in dogs. Ten dogs with confirmed
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bland embolization) has an established antitumor effect, with the prostatic carcinoma underwent PAE via a vascular approach in the
rationale being that embolization results in ischemic tumor cell left carotid artery. Tumor size was evaluated preembolization and
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death. Proponents of embolization also highlight the prevention approximately 1 month postembolization. In all dogs, prostatic
of chemotherapy toxicity. However, investigators who prefer che- tumor size decreased after embolization, and an improvement in
moembolization cite the added benefit of chemotherapy-induced clinical signs was noted based on an owner questionnaire. 45
cytotoxicity. 35 Other reported cases of embolization include a metastatic bone
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Liver embolization (Fig. 11.2) has been described in a few case lesion treated with bland arterial embolization and a cystic nasal
series in dogs, and is currently the most evaluated embolization adenocarcinoma in a cat. In the nasal adenocarcinoma case, che-
technique in companion animals. 39,40 Recently, in an experimen- moembolization using a combination of carboplatin, polyvinyl
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tal model, temporary hepatic arterial embolization was performed alcohol beads, and contrast was performed. Nasal emboliza-
using gelatin sponge particles in five dogs with normal livers and tion is regularly performed in the author’s practice as a primary
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no complications were encountered. In one study describing treatment for nasal tumors. A femoral vascular approach is used,