Outcome following curative-intent surgery for oral melanoma in dogs: 70 cases (1998–2011)

• Autores: Joanne L. Tuohy
• Localización: JAVMA: Journal of the American Veterinary Medical Association, ISSN-e 0003-1488, Vol. 245, Nº. 11, 2014, págs. 1266-1273
• Idioma: inglés
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• Resumen

  • Objective—To evaluate the outcome in terms of progression-free interval (PFI) and overall survival time (ST) after curative-intent resection of oral melanoma in dogs.

    Design—Retrospective case series.

    Animals—70 client-owned dogs.

    Procedures—An electronic medical record search and review was performed for dogs that underwent curative-intent resection of oral melanoma (May 1, 1998, to December 31, 2011). Information gathered included signalment, oral location of tumor, staging results, type of surgery, type of adjuvant therapy, findings on histologic evaluation, and outcome.

    Results—36 (51.4%), 16 (22.9%), 13 (18.6%), and 1 (1.4%) of 70 dogs had tumors classified as stage I, II, III, and IV, respectively; tumor stage could not be determined for 4 (5.7%) dogs because of the lack of tumor size information. Fifty-one (72.9%) dogs had tumors completely excised. Twenty-nine (41.4%) dogs received adjuvant therapy. Median PFI and ST were 508 and 723 days, respectively. Thirty-two (45.7%) dogs had disease progression. Significant associations with PFI or ST were found for administration of adjuvant therapy, presence of metastatic disease at the time of diagnosis, higher tumor stage (III or IV), increased tumor size (> 3 cm), and sexually intact female dogs. Administration of adjuvant treatment was associated with a 130% increased hazard (hazard ratio, 2.3; 95% confidence interval [CI], 1.0 to 5.0) of disease progression; the presence of metastases at the time of diagnosis was associated with a 281% increased hazard (hazard ratio, 3.8; 95% CI, 1.5 to 9.6) of death.

    Conclusions and Clinical Relevance—Results indicated that dogs with oral melanoma can have a long PFI and ST after resection with wide margins.

    Melanoma is the most common oral malignancy in dogs1,2 and is most frequently located in the gingiva but can be found in any location, including the lip, tongue, and palate.1–3 The appearance of oral melanomas can vary from heavily pigmented to amelanotic, and they can appear ulcerated and necrotic. Oral melanoma is an aggressive malignant tumor that is both locally invasive and highly metastatic.4,5 The most common sites of metastasis include regional lymph nodes and lungs, with the CNS and bone being less common sites.1–3,6 At diagnosis, staging tests are often performed in an effort to detect metastatic spread. Oral melanoma in dogs is staged according to the World Health Organization staging scheme, and patient stage has been shown to be prognostic.7,8 The reported STs for oral melanoma vary widely, depending on factors such as stage and type of treatment received.1,7–10 Wide resection is the most effective modality for eradication of the primary tumor.11,12 Given the aggressive biological behavior, adjuvant therapies have been recommended for oral melanoma, including chemotherapy,9,13–15 radiation therapy,16,17 and a xenogeneic DNA vaccine.18–21 Equivocal data exist regarding the efficacy of chemotherapy,14,15 and most recently, Brockley et al9 failed to demonstrate improved ST in dogs with oral melanoma with the use of adjuvant carboplatin following excision. The efficacy of the DNA vaccine is similarly equivocal, on the basis of 2 clinical reports20,21; Ottnod et al21 failed to show any survival advantage with vaccine use. Other adjuvant modalities that have been explored include liposome encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE),22 in vivo transfections of immunostimulatory genes,23 intralesional cisplatin implants,24 and local hyperthermia combined with intralesional cisplatin.25 Several prognostic factors for dogs with melanoma have been reported, including tumor size, tumor stage, histologic features such as mitotic index and nuclear atypia, and the Ki67 index.26 Many studies1,3–5,27 identifying prognostic factors and evaluating the efficacy of adjuvant therapy included a diverse patient population ranging from patients with all oral neoplasms to patients with melanomas in differing anatomic (oral, digital, and cutaneous) locations, and many of these patients underwent various treatment modalities. Limited studies have assessed outcome in a homogenous patient population with oral melanoma.

    The purpose of the study reported here was to evaluate treatment outcomes and prognostic indicators of PFI and ST following curative-intent surgery for oral melanoma in dogs. We hypothesized that location of the lesion within the oral cavity and type of resection (soft tissue alone vs bone) would influence PFI and ST. Specifically, we hypothesized that maxillary or mandibular lesions that were located more rostrally and melanomas confined within soft tissues alone and not involving bone would be associated with a longer PFI and ST. Second, we hypothesized that the presence of metastasis at time of diagnosis, higher disease stage, incomplete surgical margins, large tumor size, and lack of use of adjuvant therapy would be associated with a shorter PFI and ST.