MONOCLONAL-ANTIBODY C219 IMMUNOHISTOCHEMISTRY AGAINST P-GLYCOPROTEIN - SEQUENTIAL-ANALYSIS AND PREDICTIVE ABILITY IN DOGS WITH LYMPHOMA

In the present study, the prevalence of positive staining for P-glycop rotein using C219 monoclonal antibody was assessed in 58 tissue sample s of high-grade lymphoma from dogs before initiation of chemotherapy. Samples were also evaluated at relapse in 22 dogs, at necropsy in 34 d ogs, and at all 3 times in 15 dogs. The frequency of positive staining was significantly higher than that found prior to the initiation of c hemotherapy at the following times: relapse (P = .0001), necropsy (P < .0001), and both relapse and necropsy (P < .001, sequential data). Th e frequency of positive staining prior to the initiation of chemothera py was significantly inversely related to remission (P < .001) and sur vival times (P = .0012). Similarly, when populations below and above t he median initial C219 score were compared with respect to remission a nd survival times, the population with scores greater than the median had significantly lower remission (P < .001) and survival (P = .008) t imes, respectively. The frequency of positive staining determined at r elapse was significantly inversely related to the time from relapse to death (P = .0102). Similarly, when populations below and above the me dian relapse C219 score were compared with respect to the time from re lapse to death, the population with C219 scores greater than the media n had a significantly lower time from relapse to death (P = .006). It appears that this immunohistochemical methodology may be used as a pre dictor of remission time, survival time, and the time from relapse to death. Additional studies are required to confirm the usefulness of C2 19 as a true marker of P-glycoprotein and to evaluate P-glycoprotein a s a useful prognostic factor in dogs with lymphoma. Copyright (C) 1996 by the American College of Veterinary Internal Medicine.