Childhood leukemia as a model for cancer research: the Richard and Hinda Rosenthal Foundation Award Lecture.

Childhood acute lymphocytic leukemia (ALL) is a model for the study of disseminated cancer. It is always disseminated and relatively uniform, it is accessible to repetitive tissue sampling, and we have highly effective chemotherapy for it. The first systematic, controlled trials of cancer therapy were designed for patients with ALL by physicians with the courage and audacity to aim for cure of a "hopeless" disease. The concept of leukemia cell subpopulations in each patient received major clinical support from ALL. The pharmacological sanctuary, typified by the meninges, was first discovered and specifically attacked in ALL. Combination therapy, aggressive therapy during remission, phase-specific therapy, and the interrelationships of phases of therapy were developed first in ALL. Since leukemia cell features, such as T-cell characteristics, correlate with responsiveness to therapy, powerful new tools may be developed to improve the biological specifically of therapy. In addition to the gratifying results of therapy over the past two decades, childhood ALL continuity offers opportunities for biological research as well as improved therapy for ALL and other forms of disseminated cancer.

The importance of an isolated central nervous system relapse in children with acute lymphoblastic leukemia.

We assessed the influence of an initial isolated meningeal relapse on treatment outcome in 839 children with acute lymphoblastic leukemia (ALL) who were admitted to St Jude Children's Research Hospital (Memphis) from mid-1967 through mid-1979. The patients were entered in a series of five clinical trials (Total Therapy Studies V through IX), each designed to test one or more modifications of treatment for ALL. Two groups were compared: 699 children who received CNS prophylaxis (2,400-rad craniospinal irradiation or 2,400-rad cranial irradiation plus intrathecal methotrexate) v 56 who did not. Our results, obtained with a time-dependent covariate model and a matching technique, indicate a 2 to 3.5-fold increase in the risk of hematologic relapse or death among patients who experienced an isolated CNS relapse compared with similar patients (matched for leukocyte count and length of complete remission) who remained free of CNS involvement. Of the 107 children with an initial isolated CNS relapse, 89 (83%) have died or have had a subsequent relapse. There was no detectable difference in the rate of hematologic relapse or death after a CNS relapse between patients who had received preventive therapy and those who had not. We conclude that CNS prophylaxis is important both for the prevention of initial CNS leukemia and for reducing the risk of hematologic relapse or death subsequent to a CNS relapse.

Central nervous system morbidity following an initial isolated central nervous system relapse and its subsequent therapy in childhood acute lymphoblastic leukemia.

The frequency and types of major CNS toxicity and morbidity were analyzed in 107 children with acute lymphoblastic leukemia (ALL) following an isolated primary CNS relapse. Seventy-nine (73%) have had multiple subsequent marrow or CNS relapses requiring intensive and prolonged therapy to the CNS. Median survival time is two years. Of these 79 patients, two thirds have had one or more types of major CNS toxicity, including epileptiform seizures (35), moderate to severe structural abnormalities (24 of 27 evaluated), major motor disabilities (9), blindness (2), CNS infection (6), cranial nerve palsies (2), and intracranial lymphoma (2). The remaining 28 patients (26%) have had no or one additional CNS relapse and have received therapy for a median of eight years. One half of this surviving group of patients have had major CNS toxicity, including seizures (9), major motor disability (2), and intracranial calcifications (12/19). When neuropsychologic evaluations were compared between the 28 survivors and 50 of their contemporaries who had been in initial continuous complete remission, the CNS survivors had significantly lower Full Scale IQ scores (83 +/- 16 v 99 +/- 14, P = less than .001) with similarly lower measures of academic performance. The relative contributions of meningeal leukemia itself and intrathecal or radiation therapy to these effects cannot be determined. Since major CNS sequelae occurred in the majority of patients who had a primary isolated CNS relapse, and the frequency of CNS relapse is dependent on the efficacy of the method of CNS prophylaxis, the best method of avoiding major CNS sequelae is the most effective form of CNS prophylaxis.

Sequential changes in platelet function and coagulation in leukemic children treated with L-asparaginase, prednisone, and vincristine.

Coagulation and platelet function in 13 children with acute lymphoblastic leukemia were studied sequentially during a remission induction with L-asparaginase, prednisone, and vincristine. In the first weeks of therapy, which included four doses of L-asparaginase coagulation was characterized by significant decreases in plasma concentrations of plasminogen, antithrombin III alpha 2-macroglobulin, and fibrinogen. All measures gradually returned to normal after complication of L-asparaginase therapy. In the latter part of induction treatment, clotting times, especially partial Thromboplastin time, decreased significantly, while levels of factors V and VIII increased with recovery of platelet counts. At this time, 6 patients had an increased in vitro platelet aggregation response to adenosine diphosphate, and their partial thromboplastin times were significantly shorter than those of patients without increased aggregation. Concurrent abnormalities in coagulation and platelet function may account for the thrombotic complications that develop in some children receiving induction therapy with these agents.

Second central nervous system prophylaxis in children with acute lymphoblastic leukemia who relapse after elective cessation of therapy.

A treatment plan to achieve better disease control in patients with acute lymphoblastic leukemia (ALL) who relapse after elective cessation of therapy was assessed. The principal modifications were (1) a second preventive treatment of the central nervous system (CNS) at relapse and every six weeks throughout therapy, using intrathecal methotrexate with cytosine arabinoside, and (2) a four-week course of systemic chemotherapy given immediately before therapy was stopped a second time. Twenty-four patients were studied. There have been no meningeal relapses, in contrast to seven among 16 similar patients who were retreated without CNS prophylaxis. Although the median length of second hematologic remission was not significantly different from the outcome in the comparison group, a much higher proportion of patients (eight of 24 versus zero of 17) remain in prolonged reinduced complete remission (48-79 months). Children whose first relapse occurred later than six months after cessation of therapy had significantly longer subsequent remissions. These end results establish the value of intrathecal CNS prophylaxis in relapsed ALL and suggest that a late intensive phase of therapy will extend remissions in a substantial proportion of patients.

Risk of adverse events in children completing treatment for acute lymphoblastic leukemia: St. Jude Total Therapy studies VIII, IX, and X.

We studied the frequency, causes, and predictors of adverse events in 624 patients who had completed treatment for acute lymphoblastic leukemia (ALL) in three consecutive total therapy studies (VII, IX, and X, 1972 to 1983). Event-free survival in study X was significantly better overall than that in studies VIII and IX (P less than .0001 by the log-rank test). In study X, 75% of the patients were electively taken off therapy, compared with 54% in studies VIII and IX. However, the risks of having an adverse event during the first 5 years after completion of therapy were remarkably similar: 22% (95% confidence interval, 17% to 29%) in study X versus 24% (20% to 29%) in studies VIII and IX. Bone marrow, testicular, and CNS relapses accounted for the majority of failures in both groups (85% in study X and 92% in studies VIII and IX). Late adverse events consisted largely of hematologic relapses and the development of solid tumors. Black race (P = .001) and leukemia without an anterior mediastinal mass (P = .05) were associated with an increased risk of failure after completion of treatment in the two earlier clinical trials, whereas a lower leukemic cell DNA content (DNA index less than 1.16) was the only predictor of late treatment failure in the more recent trial (P = .019). None of the other presenting features that were examined (eg, age, leukocyte count, and sex) had value as predictors of late failure. Thus, improved treatment altered the impact of specific prognostic factors and the distribution of sites of relapse, but it did not significantly affect the risk of delayed failure.

Impact of three methods of treatment intensification on acute lymphoblastic leukemia in children: long-term results of St Jude total therapy study X.

Long-term follow-up observations are reported on 427 patients who received one of three different intensified therapies in total therapy study X for acute lymphoblastic leukemia (ALL). In the trial for 'standard-risk' ALL, 154 of 309 patients in complete remission were randomized to receive high-dose methotrexate (HDMTX, 1 g/m2) periodically during the first 72 of 120 weeks of standard continuation therapy with 6-mercaptopurine and oral MTX; the remaining 155 patients received 1800 cGy cranial irradiation and intrathecal MTX, followed by 6-mercaptopurine/MTX therapy interrupted from week 36-71 for substitution of two other pairs of drugs. At 9 years of follow-up, significantly higher proportions of patients in the HDMTX group have maintained complete remissions (64 +/- 7%, SE, vs. 52 +/- 6%, p = 0.03), hematologic remissions (73 +/- 6% vs. 62 +/- 6%, p = 0.03), and testicular remissions (94 +/- 5% vs. 80 +/- 8%, p = 0.03); however, the proportion continuing in central nervous system remission has been lower (84 +/- 5% vs 93 +/- 4%, p = 0.02). In the evaluation of teniposide/cytarabine and delayed cranial irradiation for 'high-risk' ALL, 36 +/- 9% of 101 patients are predicted to be event-free survivors at 9 years. Altogether, 217 (51%) of the 427 patients are event-free survivors after at least 7 years of follow-up (median, 9 years); an additional 75 patients are alive and free of leukemia for a median of 6.4 years after successful remission retrieval therapy, boosting the total number of long-term survivors to 292 (68%). These results establish the efficacy of HDMTX for patients with standard-risk ALL and indicate the potential of teniposide/cytarabine for use in multiagent regimens for patients with high-risk disease. The overall survival figure, 68%, affords a benchmark for other studies assessing long-term outcome in ALL.

The survivors of childhood solid tumors.

With the improvement in cancer therapy in recent years, the number of cancer survivors is rapidly increasing. Potential late medical and psychosocial sequelae of cancer therapy are reviewed. A practical guide for the primary health care giver is provided.