Duration of chemotherapy in childhood acute lymphoblastic leukaemia. The Medical Research Council's Working Party on Leukaemia in Childhood.

In three childhood acute lymphoblastic leukaemia (ALL) therapeutic trials a total of 493 patients still in first remission 18 months or 2 years after starting treatment were randomly allocated to stop treatment or continue to 3 years. Periods of 18 months or 2 years were as effective as 3 years for girls, but for boys 18 months was inferior to 3 years, although there was little difference between 2 and 3 years. These conclusions refer only to the treatment regimens employed in these trials, however, and in view of the rather different results for girls in a later trial and the high testicular and marrow relapse rates in boys, the results must be interpreted cautiously. Disease-free survival 5 years after randomisation to stop or continue treatment was 76% for girls, but only 40% for boys.