VARIABLES ASSOCIATED WITH THE PLATELET COUNT 6 WEEKS AFTER AUTOLOGOUSPERIPHERAL-BLOOD PROGENITOR-CELL TRANSPLANTATION

While abundant data exist documenting variables associated with early platelet engraftment after autologous PBPC transplantation, data conce rning later sustained platelet engraftment is sparse. We retrospective ly examined a series of 80 patients undergoing autologous PBPC transpl antation with respect to their platelet count 6 weeks after transplant . Underlying diagnoses included breast cancer (n = 33), non-Hodgkin's lymphoma (n = 32), Hodgkin's disease (n = 9), and other hematologic ma lignancies (n = 6). Patients received G-CSF for PBPC mobilization and collected a target threshold number of 2.0 x 10(6) CD34(+) cells per k ilogram. A univariate analysis revealed that a diagnosis of breast can cer, fewer courses of prior chemotherapy, younger age and complete rem ission were associated with a higher 6-week platelet count. Additional ly, the ability to collect the threshold number of CD34(+) with fewer sessions of leukapheresis was also associated with a higher 6-week pla telet count. The platelet count and the white blood cell count at the initiation of PBPC collection was also associated with a higher 6-week platelet count. A multivariate analysis revealed a higher platelet co unt on the first day of pheresis, fewer phereses required to collect 2 x 106 CD34(+) cells per kilogram, and a diagnosis of breast cancer we re all associated with a higher B-week posttransplant platelet count. Seven patients failed to reach a 6-week platelet count of 30 x 10(9)/l and an additional five patients had a platelet count of 30-50 x 10(9) /l. We conclude that underlying clinical characteristics, as well as h ematologic variables at the time of PBPC collection, influence later, sustained platelet engraftment. A percentage of patients have poor sus tained platelet engraftment and may be candidates for new cytokines th at specifically target megakaryocyte growth and development.