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Overview:
Also
commonly known as ‘injection site sarcoma, vaxosarcoma or vaccine site
sarcoma’, injection site sarcoma is an rare but aggressive type of
cancer which is linked to vaccinations, especially rabies & feline
leukemia vaccines. [1]
VAS were first observed in the late 1980’s & a link was made between the
administration of certain vaccinations & vaccine associated sarcoma in 1991
by Dr.
Mattie
Hendrick, a veterinary pathologist at the
University of Pennsylvania School of Veterinary Medicine.
She had observed sarcomas appearing at the site of vaccinations. Prior
to this in 1985 several changes to vaccinations had occurred.
Firstly, the modified live virus in the rabies vaccine was
replaced with a killed rabies vaccine, given subcutaneously (under the
skin). Adjuvants were added to help stimulate a better immune response.
Around the same time the FeLV vaccine was also introduced. In 1987 the
rabies vaccine became compulsory in Pennsylvania.
The
exact incidence is not known, but it is believed to be in the region of
1 – 10 cats per 10,000 vaccinated for rabies & FeLV. [2] Rabies & FeLV
are most commonly associated with injection site sarcoma although other
vaccines & non vaccine products have also been reported on occasion.
The
cause is still not fully understood. The adjuvant is used to hold the
antigens at the vaccine site & slowly released over a period of time,
stimulating an immune response. It is speculated that this can sometimes
lead to inflammation, which in turn may develop into cancer.
Fibrosarcomas are the most common sarcoma to develop although other
sarcomas have also been reported.
What
are the signs of VAS in cats?
The most
common symptom is a firm subcutaneous swellings at the site of the
injection. It may or may not be ulcerated. This should always be
followed up with your veterinarian.
How
is it diagnosed?
Your
veterinarian will perform a complete physical examination & obtain a
medical history from you. He will need to take a biopsy which will be
sent off to a laboratory for examination.
Aggressive action is required if the following criteria are met;
-
The lump is larger than 2cms
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The lump persists for more than 3 months after
vaccination
-
Any lump which continues to grow one month after
vaccination
Once VAS
has been confirmed, your veterinarian may also wish to perform CT to &
x-rays to determine the determine the extent of the lesion & see if the
cancer has spread (metastisised).
How
is it treated?
Vaccine
associated sarcomas are rapid growing & extremely invasive. Removal
involving a wide margin will be necessary or amputation if a limb is
affected. This will be followed by radiation therapy & occasionally
chemotherapy, although chemotherapy seems to be of little benefit.
Conclusion:
While
VAS is a serious issue it must be remembered that vaccinations have
saved millions of lives. Vaccinations are still an important aspect of
cat health. Your veterinarian is the best person to advise
you on vaccinations & you should speak to him with any concerns you may
have.
References:
[1]
Wikipedia
[2]
American Medical Veterinary Association
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