Studies :: Sarcomas

Sarcomas

Introduction

In 1996, the Vaccine Associated Feline Sarcoma Task Force was formed with the mission of determining the cause of sarcomas in cats. Many manufacturers and professional associations immediately recognized the importance of this task force and funded its efforts. One of the theories held by several experts, including members of the task force, was that vaccines, specifically those containing adjuvants, played a major role in sarcoma development.

Two landmark studies have recently been published in JAVMA. The results of these studies clearly demonstrate the low incidence of sarcomas, as well as the lack of evidence to link sarcomas to a particular brand or kind of vaccine.

Study #1 Design⁴

World Wide Web-based survey of vaccination practices, postvaccinal reactions and vaccine site-associated sarcomas in cats.

Method:

Collect data from veterinarians using a secure Web-based survey on post-vaccinal inflammatory reactions, vaccine site-associated sarcomas, and detailed information and history on each sarcoma.

Results:

• 93 veterinarians completed the study
• 31,671 cats were enrolled
• 61,747 doses were administered to these cats
• Two sarcomas were within the specifications set by the study design:
  • One with an adjuvanted rabies vaccine
  • One with a non-adjuvanted distemper-leukemia combination vaccine

Study #2 Design⁵

(Supported by the Vaccine Associated Feline Sarcoma Task Force)

Multicenter case-control study of risk factors associated with development of vaccine-associated sarcomas in cats.

Method:

Medical histories collected from veterinarians submitting biopsy specimens from cats with a confirmed diagnosis of soft tissue sarcoma or basal cell tumor.

Results:

No single vaccine brand or manufacturer within antigen class was found to be associated with sarcoma formation.

Commentary

Study #1 demonstrated sarcomas can occur with adjuvanted and non-adjuvanted vaccines, dispelling the belief that sarcomas are caused by adjuvants. Other important study points to note:

• Results of this study do not support the contention that vaccine site-associated sarcomas are as common as has been suggested.
• The findings from this study concerning transitory post-vaccinal reactions should be reassuring to practitioners. Approximately 98 percent of the post-vaccinal reactions resolved without medical intervention. Ninety-six percent resolved within three months and 100 percent within four months of vaccination.
• Such information should help to minimize or alleviate the concerns of pet owners who consider declining vaccination for fear of a sarcoma developing.

Study #2 findings did not support the hypothesis that specific brands or types of vaccines within antigen class either increased or decreased the risk of vaccine-associated sarcoma formation in cats. There was evidence to suggest certain long-acting injectable medications may be associated with sarcoma formation.⁵

These two studies clearly show using vaccines without adjuvants does not improve safety, as sarcomas are not caused by adjuvanted vaccines. We must now focus our attention on other independent research to better define the potential causes and solutions for the sarcoma issue, including the role of genetics in predisposing some cats to sarcoma occurrence.