In vitro drug resistance profiles of adult versus childhood acute lymphoblastic leukaemia

The difference in the current cure rates between adult and childhood acute lymphoblastic leukaemia (ALL) may be caused by differences in drug resistan ce. Earlier studies showed that in vitro cellular drug resistance is a stro ng independent adverse risk factor in childhood ALL. Knowledge about cellul ar drug resistance in adult ALL is still limited. The present study compare d the in vitro drug resistance profiles of 23 adult ALL patients with that of 395 childhood ALL patients. The lymphoblasts were tested by the MTT assa y. The group of adult ALL samples was significantly more resistant to cytos ine arabinoside, l-asparaginase, daunorubicin, dexamethasone and prednisolo ne. The resistance ratio (RR) was highest for prednisolone (31.7-fold) foll owed by dexamethasone (6.9-fold), l-asparaginase (6.1-fold), cytosine arabi noside (2.9-fold), daunorubicin (2.5-fold) and vincristine (2.2-fold). Lymp hoblasts from adult patients were not more resistant to mercaptopurine, thi oguanine, 4-HOO-ifosfamide, mitoxantrone and teniposide. There were no sign ificant differences in drug resistance between adult T-cell (T-) ALL (n = 1 1) and adult common/pre-B-cell (B-) ALL (n = 10). Additionally, adult T-ALL did not differ from childhood T-ALL (n = 69). There were significant diffe rences between adult common/pre-B-ALL and childhood common/pre-B-ALL (n = 3 10) for prednisolone (RR = 302, P = 0.008), dexamethasone (RR = 20.9, P = 0 .017) and daunorubicin (RR = 2.7, P = 0.009). Lymphoblasts from adults prov ed to be relatively resistant to drugs commonly used in therapy. This might contribute to the difference in outcome between children and adults with A LL.