WM Crist

PURPOSE: To define more uniform criteria for risk-based treatment assignment for children with acute lymphoblastic leukemia (ALL), the Cancer Therapy Evaluation Program (CTEP) of the National Cancer Institute (NCI) sponsored a workshop in September 1993. Participants included representatives from the Childrens Cancer Group (CCG), Pediatric Oncology Group (POG), Dana-Farber Cancer Institute (DFCI), St Jude Children's Research Hospital (SJCRH), and the CTEP. METHODS: Workshop participants presented and reviewed data from ALL clinical trials, using weighted averages to combine outcome data from different groups. RESULTS: For patients with B-precursor (ie, non-T, non-B) ALL, the standard-risk category (4-year event-free survival [EFS] rate, approximately 80%) will include patients 1 to 9 years of age with a WBC count at diagnosis less than 50,000/microL. The remaining patients will be classified as having high-risk ALL (4-year EFS rate, approximately 65%). For patients with T-cell ALL, different treatment strategies have yielded different conclusions concerning the prognostic significance of T-cell immunophenotype. Therefore, some groups/institutions will classify patients with T-cell ALL as high risk, while others will assign risk for patients with T-cell ALL based on the uniform age/WBC count criteria. Workshop participants agreed that the risk category of a patient may be modified by prognostic factors in addition to age and WBC count criteria, and that a common set of prognostic factors should be uniformly obtained, including DNA index (DI), cytogenetics, early response to treatment (eg, day-14 bone marrow), immunophenotype, and CNS status. CONCLUSIONS: The more uniform approach to risk-based treatment assignment and to collection of specific prognostic factors should increase the efficiency of future ALL clinical research.

Chromosome translocations involving band 11q23 are associated with human acute leukemias. These translocations fuse the ALL-1 gene, homolog of Drosophila trithorax and located at chromosome band 11q23, to genes from a variety of chromosomes. We cloned and sequenced cDNAs derived from transcripts of the AF-4 and AF-9 genes involved in the most common chromosome abnormalities, t(4:11)(q21:q23) and t(9:11)(p22:q23), respectively. Sequence analysis indicates high homology between the AF-9 gene protein product and the protein encoded by the ENL gene fused to ALL-1 in (11:19) chromosome translocations. AF-4, AF-9, and ENL proteins contain nuclear targeting sequences as well as serine-rich and proline-rich regions. Stretches abundant in basic amino acids are also present in the three proteins. These results suggest that the different proteins fused to ALL-1 polypeptide(s) provide similar functional domains.

The prognostic significance of chromosomal translocations, particularly t(1;19) (q23;p13), was evaluated in children with pre-B and early pre-B acute lymphoblastic leukemia (ALL). Patients were treated on a risk-based protocol of the Pediatric Oncology Group (POG) between February 1986 and May 1989. An abnormal clone was detected in 46% (130 of 285) of pre-B cases and 56% (380 of 679) of early pre-B cases. Translocation of any type was associated with a worse treatment outcome than other karyotypic abnormalities: 15 of 66 versus 3 of 64 failed therapy in the pre-B group (P = .001), and 37 of 141 versus 23 of 239 failed in the early pre-B group (P less than .001). The t(1;19) (q23;p13) occurred significantly more often in cases of pre-B ALL with a clonal abnormality than in early pre-B ALL cases (29 of 130 v 5 of 380, P less than .001). Among the 285 pre-B cases in which bone marrow was studied cytogenetically, those with t(1;19) had a significantly worse treatment outcome than all others (11 of 29 v 27 of 256 have failed therapy, P less than .001). This difference is significant (P less than .001) after adjustment for leukocyte count, age, and other relevant features. Cases with the t(1;19) also had a worse prognosis than pre-B patients with other translocations (4 of 37 have failed, P less than .01) or with any other karyotypic abnormality (7 of 101 have failed, P less than .001). We conclude that chromosomal translocations confer a worse prognosis for non-T, non-B-cell childhood ALL, and that the t(1;19) is largely responsible for the poor prognosis of the pre-B subgroup.