“The efficacy of the melanoma vaccine in CMM and the potentials for application of the vaccine in other domestic animals”

Introduction: canine malignant melanoma (CMM) is a common, aggressive and potentially metastatic tumour that typically caries a grave prognosis. Melanoma in cats is relatively uncommon, but caries the same poor prognosis, in contrary to horses where many animals will be affected by it and generally have benign tumours. MSTs of 1-5 months in CMM treated with standard therapy protocols have been previously reported. Xenogeneic DNA vaccines used as a treatment in CMM have shown to induce both humoral and cellular immune responses and may cause regression of the tumour and to increase survival time. Aim of the study: The aim of the study was to determine the efficacy of the xenogeneic human tyrosinase DNA vaccine as an adjunctive therapy in CMM and the therapeutic potential for the use of this vaccine in other animal species, mainly cats and horses. It was expected that this melanoma vaccine would considerably lengthen MSTs. Materials and Methods: A total of 21 dogs have been examined since February 2011, 2 of which were misdiagnosed as CMM. Therefore 19 dogs (13 male and 6 females) were included in the statistical analysis; 13 oral -, 5 non-oral malignant melanoma and 1 metastatic melanoma, with the primary tumour unidentified. The following protocol was used; after confirmation of the tumour as a CMM and clinical staging using the WHO TNM system, the tumour was surgically removed, followed by local radiation therapy. The xenogeneic human tyrosinase vaccine was administered in 4 doses, every other week. Subsequently, the patients received physical examinations and radiographs/CTscan to a preset protocol, at 1, 3 and 6 months after the final vaccination, to check for signs of recurrence and metastases. Results: The mean ST of all 19 dogs was 437 days from the start of treatment. Stage 1 and 2 dogs had significantly longer STs compared with stage 3 and 4 dogs (P = 0.042). The mean RFI was 468 days, the mean MFI was 268 days and the mean DFI was 326 days. No median ST times could be calculated because the 0.5 cumulative survival was not reached, as 12 of 19 dogs were still alive at the end of the study. Discussion: The study data are not yet complete, therefore median ST and several other parameters were not yet available for interpretation, which made comparing the results to previously reported results difficult. Vaccinations generally occurred without difficulty or local irritation. One dogs developed a superficial bacterial dermatitis during the course of the study, which probably was unrelated to the vaccine therapy. It must be considered positive that many dogs survived considerably longer than would be expected in those treated with conventional treatment modalities. More research is needed on the efficacy of the xenogeneic DNA vaccine in CMM and also on the therapeutic potential of xenogeneic DNA vaccines in feline and equine because it is very well possible that positive effects are found in further investigations