Page 1410 - Clinical Small Animal Internal Medicine

1348 Section 11 Oncologic Disease

melanoma. Interestingly, BRAF mutations are also Cutaneous melanocytomas are often completely
VetBooks.ir uncommon in canine oral malignant melanoma, sug- excised with 1 cm lateral skin and one fascial plane deep
margins. In contrast, partial mandibulectomy and maxil-
gesting that certain canine and/or feline malignancies
can have similar molecular signatures in addition to their
oral melanomas arising from the gingiva or from other
already well‐known clinical similarities in the context of lectomy are typically required for complete removal of
resistance to chemotherapy and/or radiation, prognosis, oral mucosa in close proximity to bone. Imaging via
and similar variable peculiar sites of metastatic propen- computed tomography (CT) or magnetic resonance
sity. A number of other investigators have reported a imaging (MRI) can be helpful for delineation of tumor
variety of molecular abnormalities and/or associations in extent/invasiveness and/or involvement of regional
canine and feline melanoma. lymph nodes. Melanomas in mucosal areas not adjacent
to bone such as tongue, lip or buccal mucosa may be
amenable to excision of the soft tissues only. Local recur-
Staging rence rates vary from ~20% to 50% following man-
dibulectomy and maxillectomy, respectively. Quality of
The staging of dogs with melanoma is relatively straight- life is typically very good to excellent and most dogs are
forward. A minimum database should include a thor- eating in the first day or two following mandibulectomy
ough history and physical exam, complete blood count or maxillectomy, with high owner satisfaction rates. The
and platelet count, biochemical profile, urinalysis, three‐ combination of surgery and radiation plus adjuvant ther-
view thoracic radiographs and local lymph node apy should be considered in those patients with tumors
aspiration with cytology to determine whether lymphad- that are not amenable to clean margin resection.
enomegaly is present or not. Williams and Packer
reported that local nodes from dogs with oral melanoma Radiation Therapy
have ~70% metastasis when lymphadenomegaly was pre-
sent, but more importantly, ~40% had metastasis when Radiation therapy can play an integral role in the treat-
no lymphadenomegaly was present. Abdominal ultra- ment of a subset of canine and feline melanomas.
sound should be considered in cases with moderate to Radiation therapy is unfortunately ineffective at
high metastatic potential such as the oral cavity, feet or controlling distant metastasis and therefore should be
mucosal surface of the lips, as melanoma may metasta- used for local tumor control when definitive local ther-
size to the abdominal lymph nodes, liver, adrenal glands, apy via surgical removal is incomplete or not possible.
and other sites. Melanoma has historically been believed to be a
The use of sentinel lymph node mapping and lym- relatively radioresistant tumor type. Therefore, most
phadenectomy is of diagnostic, prognostic and clinical radiation protocols used in dogs and cats have utilized
benefit in human melanoma. Relatively few investiga- higher doses per fraction. Protocols with fewer treat-
tions have been reported to date for sentinel lymph node ments (“hypofractionated”) have less cost, reduced
mapping and/or excision for dogs with malignancies and emotional and time commitment for owners, and fewer
this author strongly encourages additional investigation anesthetic episodes with generally less severe acute side‐
in this area. Furthermore, the use of novel staging effects when compared to full‐length normally fraction-
modalities such as gallium citrate scintigraphy is also ated protocols. A 2–3 cm margin around the tumor is
encouraged. typical for most radiation plans with considerations for
irradiation of the local draining lymph node.
The overall response rate to radiation for canine OMM
Therapy is generally 80–90% with approximately 60% complete
response and 25% partial responses. Progression‐free
median survival times with radiation are typically 5–8
Surgery
months with high recurrence rates. Median survival
Surgery is the most effective local treatment modality for times range from approximately five to 12 months. Dogs
melanoma. Incisional biopsy is an important part of the with less advanced, incompletely resected oral mela-
diagnostic work‐up based on the clinical, therapeutic, noma (majority were stage I with some stage II) that were
and prognostic heterogeneity of tumors on the differen- treated with either carboplatin or cisplatin given once
tial diagnosis list. In cases for which cytology results weekly before radiation therapy had a median survival
from draining lymph nodes are equivocal, lymph nodes time of approximately 12 months. The median survival
should be surgically excised and submitted for patho- time for five cats with oral malignant melanoma treated
logic examination as this outcome holds prognostic and with radiation therapy and a variety of other adjuvant
therapeutic importance. therapies was only 146 days.