Randomized study of 3 years versus 5 years of chemotherapy in childhood acute lymphoblastic leukemia.

Between 1972 and 1975 the Children's Cancer Study Group conducted two clinical trials for the treatment of newly diagnosed patients with acute lymphoblastic leukemia. Upon achieving 3 yr of continuous complete remission, 316 children and young adults were randomly allocated either to discontinue chemotherapy or to continue chemotherapy for an additional 24 mo. With a median follow-up from the time of randomization of 50 mo, those patients who received 3 yr of therapy have demonstrated a statistically non-significant yet higher incidence of bone marrow relapse as compared to those patients treated for 5 yr (p = 0.09). However, the proportion of patients surviving 5 yr from randomization is 93% for the 3-yr treatment group and 89% for the 5-yr treatment group (p = 0.27). No significant difference was observed between the randomized groups for the occurrence of testicular relapse (p = 0.12), central nervous system relapse (p = 0.17), or first occurrence of relapse or death (p = 0.24). The relapse-free survival of patients treated for 5 yr as compared to those treated for 3 yr was not significantly higher in males (81% versus 75%, p = 0.14) or females (89% versus 89%, p = 0.95). This randomized study did not demonstrate a significant difference between treatment for either 3 or 5 yr.