OBJECTIVES

Immunotherapy may provide an effective method of cancer treatment, either alone or in conjunction with surgery, chemotherapy or other approaches leading to tumour reduction. Despite its theoretical efficacy and long history of clinical application, immunotherapy in companion animals is still poorly investigated. The objective of this study was to evaluate the efficacy of immunotherapy induced by poxvirus (Baypamun DC) as an adjuvant therapy to surgical resection of canine mammary tumours.

MATERIALS

Twenty-six bitches of various breeds presenting malignant mammary tumours were attended at the Veterinary Hospital of University Paulista (UNIP, São Paulo, Brazil) and divided into 2 groups - those submitted to surgical procedure alone (group I, n =10) and those in which was used the association of surgical and immunotherapeutic treatment (group II, n =16). Depending on the specific case, the surgical procedure consisted of simple mastectomy, en bloc resection or complete unilateral mastectomy. Eight doses (1ml each one, by subcutaneous route) of the immunomodulator Baypamun DC were used according to the following periods - one week before surgery; on the surgery day; 7, 14, 21, 28, 43 and 58 days post-excision. Mammary tumours were assigned based on the result of clinical examination and the WHO Tumour-Node-Metastasis (TNM) classification scheme. Such animals were randomly distributed in groups. For a period of 2 years each bitch was regularly monitored both clinically and by laboratory tests for neoplasms and the development of local recidives and metastases in lymph nodes and other organs.

RESULTS

In all cases, mammary tumours were detected by the owner one month to one year before the first clinical examination. The mean age of the 26 dogs at diagnosis was 9 (±1,5) years and there was no statistical association between these tumours and history of pseudopregnancy, parity, estrus irregularity and anti-conception therapy. According to WHO criteria for neoplastic classification, group I presented 2 bitches with tumours assigned as TNM stage I, 4 with TNM stage II and 4 with stage III. Histopathological classification of these tumours resulted in 7 cases of tubulopapillary carcinomas and 3 cases of solid carcinomas. Lymph node or lung metastases were not found in none of these patients before surgery, but one year after surgical resection, 5 animals (50%) presented local recurrences and metastases, and euthanasia was demanded by the owner. In group II, 4 bitches had tumours with TNM stage I, 6 with stage II and 6 with stage III. Histopathological analysis showed 10 tubulopapillary carcinomas, 4 solid carcinomas and 2 sarcomas. There were no detectable metastases in lymph nodes or in any other tissue in group II, probably suggesting a decrease in the risk of neoplastic dissemination. Only one bitch presented local recurrence (6 months after surgery) and this female is still under treatment with Baypamun DC (one dose monthly), with no further neoplastic growth. After the immunomodulator first dose, tumours were less adherent and more encapsulated and apparently they stopped to grow.

CONCLUSION

Thus the present study showed that a combination of surgery and use of Baypamun DC revealed to be a better method of therapy for malignant canine mammary neoplasia than tumour resection alone. The laboratory data and the results of the clinical examinations suggest that surgery alone may be not sufficient to cause partial or total remission of these tumours.