A new study sheds light on risk factors for the development of these tumors.
What they did
Using client questionnaires to obtain histories of vaccine and other injections, researchers prospectively evaluated 436 feline masses: 181 soft tissue sarcomas, 96 tumors at nonvaccine sites (control group 1), and 159 basal cell tumors (control group 2). A third control group was formed by combining control groups 1 and 2.
What they found
A history of intrascapular administration of long-acting corticosteroid injections was associated more often in cats with sarcomas than in the controls. Among the 56% of cats with sarcomas that had received vaccines in that area, there was no difference in risk between inactivated and modified-live vaccines. Cats with sarcomas in the rear limb region were more likely to have received inactivated vs. recombinant vaccines, but neither vaccine was found to be risk-free.
Recombinant vaccines may be less likely to induce sarcoma formation, but no vaccine was found to be risk-free. Injections of long-acting corticosteroids were also associated with sarcoma formation.
Srivastav A, Kass PH, McGill LD, et al. Comparative vaccine-specific and other injectable-specific risks of injection-site sarcomas in cats. J Am Vet Med Assoc 2012;241(5): 595-602.
Link to abstract: http://avmajournals.avma.org/doi/abs/10.2460/javma.241.5.595