Monitoring of minimal residual disease (MRD) after multidrug chemotherapy and its correlation to outcome in dogs with lymphoma: a proof-of-concept pilot study.
BACKGROUND
Tumor cell burden in dogs with lymphoma cannot be assessed accurately by diagnostic evaluation during clinical complete remission (CR). Recent advances in polymerase chain reaction (PCR)-based methods enabled us to quantify minimal residual disease (MRD) in canine lymphoma.


OBJECTIVE
To quantify MRD in dogs with lymphoma treated with multidrug chemotherapy and to correlate it with remission duration after chemotherapy.


METHODS
Seventeen dogs with lymphoma that achieved CR by multidrug chemotherapy.


METHODS
Rearranged immunoglobulin heavy chain or T-cell receptor gamma chain gene fragments from lymphoma cells were PCR amplified and sequenced to prepare clone-specific primers and probes for real-time PCR to quantify MRD. MRD in the peripheral blood was monitored during and at the end of a 25-week multidrug chemotherapy protocol. Correlation between MRD at the end of chemotherapy and remission duration after chemotherapy was analyzed.


RESULTS
MRD gradually decreased after initiation of multidrug chemotherapy, reached a nadir as low as <0.019-1.0 cells/microL at weeks 4-17, and remained low or slightly increased until week 25. MRD at the end of chemotherapy was negatively correlated with remission duration from the end of chemotherapy to relapse.


CONCLUSIONS
MRD could be an objective marker to indicate tumor cell burden in dogs with lymphoma even in clinical CR. MRD at the end of chemotherapy could be a prognostic factor to predict remission duration after chemotherapy.
Yamazaki
J
J
Department of Veterinary Internal Medicine, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Takahashi
M
M
Setoguchi
A
A
Fujino
Y
Y
Ohno
K
K
Tsujimoto
H
H
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D008223:Lymphoma / Q000188:drug therapy / Q000662:veterinary*; D018365:Neoplasm, Residual / Q000662:veterinary; D010865:Pilot Projects; D016896:Treatment Outcome