The effectiveness of a human tyrosinase DNA vaccine in dogs with CMM and the possible effects of this vaccine on unborn fetuses when administered during gravidity

Abstract

Canine Malignant Melanoma (CMM) is an aggressive tumor, which mostly affects the oral cavity, mucocutaneous junctions and digits in the dog. It metastasizes very quickly, mainly to the regional lymph nodes and lungs. Especially the metastases are poorly responsive to conventional therapy. The average median survival time of CMM patients after conventional treatment is 2 to 14 months, dependent of the severity of disease (12 to 14 months for stage I dogs, <5 months in stage II dogs, and 2 to 3 months in stage III and IV dogs).

This study investigates the effectiveness of the administration of a xenogeneic DNA vaccine, containing a human tyrosinase encoding sequence, in addition to the conventional therapies of surgery and radiation therapy. The hypothesis is that the use of this vaccine will increase both survival time (ST) and quality of life in CMM patients.

In this study 19 dogs were included since February 2011, of which 13 were male and 6 were female. Of these dogs, 5 were classified as stage I, 3 as stage II, 7 as stage III and 4 as stage IV. All dogs underwent surgical excision of the primary tumor (and affected lymph nodes if present), 6 x 6 Gy radiation therapy of the excision site and 4 x the administration of the Oncept ® vaccine.

During this study (from February 2011 to October 2012) 7 dogs died of which 4 from melanoma disease. The mean ST for all 19 dogs was 437 days, with the 0.5 cumulative survival not yet reached. Therefore, calculating a median ST was not possible yet. The ST for stage I+II patients was significantly longer than the ST for stage III+IV (P=0.042). Data such as Recurrence Free Interval (RFI), Metastasis Free Interval (MFI) and Disease Free Interval (DFI) were also estimated.

As the median is still not reached after 1.5 years, the Oncept ® vaccine seems to positively influence the ST of CMM patients. However, to make definite conclusions about the effectiveness of this vaccine, the median should be reached so that a median ST can be calculated. Further investigation on this subject is therefore recommended.