Finding and treating oral melanoma, squamous cell carcinoma, and fibrosarcoma in dogs - Veterinary Medicine
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Finding and treating oral melanoma, squamous cell carcinoma, and fibrosarcoma in dogs
The three malignancies most likely to occur in dogs' mouths can have devastating local or metastatic effects if not identified and treated quickly. Review how surgery—in conjunction with radiation, chemotherapy, or vaccination—may increase your patients' survival times.


Partial maxillary resection in the control of oral squamous cell carcinoma has also been investigated. One study reported a MST of 19.2 months for seven dogs treated with hemimaxillectomy.20 Another study evaluating six dogs treated with partial maxillectomies found a MST of only 3.5 months, with 83% of dogs dying because of their disease, 50% having local recurrence.11 These studies' discordant results may be due to a low number of cases in each study or differences in the aggressiveness of the treatments provided. A third study showed a one-year survival of 84% in 19 dogs treated with surgery for squamous cell carcinoma; 16 (84%) of these tumors affected the mandible. Local recurrence rate was low at 5%, with 11% developing metastatic disease.22

Overall, it appears that mandibulectomies and, possibly to a lesser extent, maxillectomies can be effective in both decreasing disease recurrence and prolonging MST. In contrast to dogs with melanoma, dogs with squamous cell carcinoma that die of their disease will usually die of local, not systemic, disease.

5. The same dog as in Figure 2 three months after a partial glossectomy. At this time, the patient was eating and drinking normally.
Lingual—Lingual squamous cell carcinoma can also be treated successfully with aggressive surgery (Figure 5). As far as functionality after surgery, an earlier study reported that 40% to 60% of the tongue can be excised with good patient outcome.29 A more recent report described five dogs with lingual resection of 80% to 100% that had an excellent quality of life after a brief adaptation period.40

Only limited reports describe the survival of dogs with lingual squamous cell carcinoma treated surgically. Out of 21 dogs with lingual squamous cell carcinoma in one study, only four cases were treated with surgery alone. Two were euthanized within two months for local recurrence and nodal metastasis, while two lived more than 35 months.12 In another study involving eight dogs treated for lingual squamous cell carcinoma, 50% of the dogs were alive and free of disease, with last follow-up at six, 12, 16, and 27 months postoperatively. Two of the dogs had also received mitoxantrone chemotherapy after surgery.29 Since these studies were conducted in the mid-1980s and early 1990s, respectively, they do not reflect changes in patient care that have occurred recently and, thus, may underestimate survival times in dogs treated for lingual squamous cell carcinoma today.

Tonsillar—Tonsillar squamous cell carcinomas are extremely aggressive locally with an increased rate of metastasis compared with their nontonsillar counterparts. Surgical resection alone is a poor treatment option since most affected dogs have lymph node metastasis at presentation. Additionally, because of tumor location and invasiveness, complete removal of the primary tumor is challenging to impossible. In three dogs, tonsillectomy alone resulted in survival times of one, nine, and 38 days.3 Unfortunately, even with multimodality therapy, the prognosis for tonsillar squamous cell carcinoma remains poor.27,28

Fibrosarcoma. Similar to nontonsillar squamous cell carcinoma, surgery is the primary treatment option for fibrosarcoma. In one study, 19 dogs with fibrosarcoma treated with a partial mandibulectomy alone had a median disease-free interval of 10.6 months, with a one-year survival rate of 50%.16 Twelve of these 19 (63%) dogs died during the course of the study, with 11 of the 12 (92%) having local recurrence.16 Two additional studies evaluated three and 16 dogs with stage III or IV oral fibrosarcoma treated with varying mandibular resections and showed survival times of 16 months (mean) and 11 months (median), respectively.13,39 Local recurrence was 75% in the three-dog study compared with 31% in the 16-dog study. This difference in local recurrence rate may be explained by varying surgical techniques and aggressiveness as well as a small population size in each study.

Resection of maxillary fibrosarcoma has also been evaluated. Twenty-nine dogs with fibrosarcoma treated with partial maxillectomies reported in two studies experienced MSTs of 9.5 to 12.2 months. Seventeen of the 29 (59%) dogs died of their disease, with 14 of the 29 (48%) having local recurrence.11,20 The one-year survival rate of 14 dogs treated surgically for fibrosarcoma (seven mandible, seven maxilla) in a third study was 50%. Local recurrence occurred in 36% of the dogs, and 14% of the cases showed metastasis.22

As a compilation, these studies show that surgical removal of fibrosarcoma is important as a first-line modality, but because of the high percentage of recurrence of local disease, adjunctive therapy such as radiation may be necessary to further prolong survival. However, a recent study evaluated 38 dogs with oral fibrosarcoma, 29 of which were treated with surgery alone.41 The tumors were distributed fairly equally between the mandible and maxilla and also between caudal and cranial locations. This group had a MST of 1,024 days, which was much improved over earlier reports. Better preoperative imaging abilities and improved surgical techniques were theorized to be the reasons behind the improved results.41 Overall, aggressive surgical resection is needed to control oral fibrosarcoma, and radiation therapy may be needed in cases in which such resection is not possible.


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