Introduction: The study of multiple primary tumors in the dog is an important adjunct to the studies in man; these studies are also justified on a companion animal medicine basis. Spontaneous multiple primary tumors do occur in domestic animals, specially in dogs, probably in sufficient numbers to permit analytic studies, but since the date there are only a few studies about that.

Materials and Methods: The tumor series were derived from the hospital-based cancer registry of the Veterinary Teaching Hospital, U.C.M. (Madrid, Spain) from January 1991 through December 2003. The reference population consisted of animals brought to the hospital for any reason during the same period. The main information available from the register comprises basic characteristics of the patient (age, breed and sex), primary site and histological type of the tumour. The registry is tumour based and multiple primaries occurring in the same patient are included only if they follow the IARC/IACR rules.

Results: In the registry with 2724 case records, the percentage of patients with at least one additional tumor was 17.9%. The multiple primary tumors (MPN) data base consisted of 488 cases representing 1128 histologically confirmed neoplasms. This was an average of 2.3 neoplasms per MPN case. The percentage of females was 77.2% and 22.7% were males. The average age at first tumor diagnosis was 9.6 years. For the animals in the reference population, the average age was 5.09. For the dogs with only a single neoplastic submission the average age was 9 years. The breed with a highest number of multiple primaries was the poodle (26.7%) followed by cocker spaniel (23.18%), Yorkshire terrier (22.5%) and boxer (19.5%). When specific cancer sites were considered the most frequent tumours associations were different by sex. In females the more common association was breast and breast; in males was genital system and skin.

Discussion: The present work is the first step in our research and has mainly a descriptive value. Nevertheless, the preliminary findings are consistent with the results of previous epidemiological studies and show the utility of the use of hospital registry data in identifying a sufficient number of multiple primary cancer patients and facilitated case-control comparisons.

References

1.  Bender, A.P. An epidemiological study of canine multiple primary neoplasia. Dissertation, The Ohio State University, 1980.

2.  Mulligan, R.M. Multiple primary tumors in dogs. Cancer research 4: 505-509, 1944.

3.  Priester, W.A. Multiple primary tumors in domestic animals. A preliminary view with particular emphasis on tumors in dogs. Cancer, 40: 1845-1848, 1977.