This study reports the outcome after relapse of acute lymphoblastic leukemia (ALL) in a population-based study of 809 children over 1 year of age diagnosed July 1981 through June 1986 and with non-B acute lymphoblastic leukemia in the five Nordic countries. By January 1994, 315 children had suffered at least one relapse. The bone marrow was involved in 216 cases. There were 69 isolated CNS relapses, 25 isolated testicular recurrences and five relapses in other extramedullary sites. Of the 315 children with relapse, 94 are still in a second complete remission 12-138 (median: 78) months after relapse. The overall probability of a second event free survival (P-2.EFS) and survival after relapse was 0.28 and 0.33 respectively. The probability of remaining in second remission at 11 years was significantly correlated to the duration of first remission (P < 0.001), the site of relapse (P < 0.001) and gender (P = 0.004). The P-2.EFS for early, intermediate, and late bone marrow involved relapses were 0.08, 0.19, and 0.50 respectively. For early, intermediate and late isolated CNS relapses the P-2.EFS were 0.21, 0.38 and 0.61, respectively. The P-2.EFS for boys with isolated testicular relapses was 0.69. Girls with isolated CNS relapse (P < 0.001) and with bone marrow involved relapse (P = 0.04) had a significantly better prognosis than boys. Children with initial high risk criteria, especially T-ALL and mediastinal mass who relapsed, had a very poor prognosis.
Conclusion: In this population-based study, about 30% of children with ALL obtained a long second remission and possible cure.