Lymphoma, one of the most common neoplasms in the dog, can arise in any
tissue in the body but tends to appear in lymphoid tissues, such as lymph
nodes, spleen and bone marrow. It primarily occurs in middle-aged dogs (6-9
years of age). Lymphoma is classified by where it is located, the
histologic criteria, and the immunophenotypic characteristics of the
lymphocytes, of which the two most common phenotypes are B-cell and T-cell,
with 75-80% of those reported as B-cell. These classifications are
important in determining prognosis and treatment options. The oncologist
will explain all of this at your oncology consultation.
Prognosis depends on many different factors. Untreated lymphoma typically
progresses rapidly, going from presentation to terminal stages within 1 to 2
months. Lymphoma is rarely curable (less than 10% of cases), however
considerable improvement in duration and quality of life can be seen in dogs
treated with chemotherapy. A common chemotherapeutic protocol for treating
canine B-cell lymphoma, CHOP or modified CHOP, typically results in an
80-90% remission rate with a median survival time of 12 months. However,
only approximately 25% of dogs that respond to this protocol will be
long-term survivors (>2 years). Therefore, a majority of dogs require
repeated chemotherapeutic intervention, with highly variable response rates
to maintain remission state.
The development of an exogenous antibody vaccine that targets native surface
antigens on B-cells has sparked a revolution in the treatment of B-cell
lymphoma in humans. The antibody is directed against an antigen found on
the surface of B cells, and has been shown to be an excellent target for
passive immunotherapy. Thus, a vaccine to induce antibodies that target the
same antigen has been produced for canine patients. DNA cancer vaccines
offer a safe adjunct to existing therapies with the potential to induce
longer term remissions.
Canine Lymphoma Vaccine, DNA, is indicated for the therapeutic immunization
of dogs diagnosed with Large B-cell Lymphoma upon achieving remission
through chemotherapy. The challenge with many cancers is that the host does
not recognize the neoplastic cells as "foreign", so the immune system is not
elicited to defend the body against the neoplastic cells. Upon vaccination
with the lymphoma vaccine, the antigen is taken up by the host cells and is
then transcribed in the host and actively presented to the immune system.
The immune system recognizes the form as foreign and procedures an immune
response thus leading to destruction of the neoplastic B-cells. Studies of
the vaccine have shown significantly improved survival times (>734 days)
over dogs treated with chemotherapy alone (approximately one year).
Initial treatment with the canine lymphoma vaccine is four doses of vaccine
at two-week intervals, followed by a booster dose at six-month intervals.