Relation of cellular drug resistance to long-term clinical outcome in childhood acute lymphoblastic leukaemia

The clinical relevance of cellular drug resistance in children with acute lymphoblastic leukaemia (ALL) is unknown. The relation between in-vitro sensitivity to chemotherapeutic drugs at initial diagnosis and long-term clinical outcome was investigated in 44 children with ALL. The short-term MTT assay was used to assess sensitivity to prednisolone, vincristine, colaspase (asparaginase), daunorubicin, and thioguanine (instead of mercaptopurine which is unstable in vitro). For vincristine and colaspase there was no difference in outcome (probability of continuous complete remission) between sensitive and resistant patients. However, the probability of continuous complete remission was significantly lower in patients with resistant cells than in those with sensitive cells for thioguanine (p