Michael R. Grever

N 1988, THE National Cancer Institute-sponsored Working Group (NCI-WC) on chronic lymphocytic leukemia (CLL) published guidelines for the design and conduct of clinical trials in CLL with two major objectives: first, to facilitate comparisons of results of clinical trials in CLL by providing standardized eligibility, response, and toxicity criteria; and, second, to encourage a framework on which to evaluate new scientific studies related to our increasing understanding of the biology and immunology of this disease.' These guidelines were rapidly adopted by the majority of the clinical trials community, and were also used by the Food and Drug Administration during its evaluation process for the approval of fludarabine. The differences between these guidelines and those subsequently published by the International Working Group on CLL (IWCLL), which were general-practice recommendations' are listed in Table 1. For diagnosis, the NCI-WC requires a lymphocyte count of 5 X loy& which is lower than the 10 X 109/L required by the IWCLL, unless the lymphocytes are B cells and the bone marrow is involved. To be considered a complete remission (CR), the NCI-WC criteria specify that less than 30% lymphocytes must be present in the bone marrow, with a recommendation that the clinical significance of lymphoid nodules be assessed prospectively (Table 1); the IWCLL allows focal infiltrates or nodules in the bone marrow aspirate and biopsy for CR. The IWCLL uses a shift in clinical stage as the sole index of partial remission (PR), whereas the NCI-WC provides more specific criteria and recommends validation of the relevance of stage shift. The major differences were the well-defined criteria in the NCI guidelines regarding when to initiate therapy, hematologic toxicity, and other important components for clinical trials design. The purpose of this report is to present those revisions as considered necessary in view of advances in the past 8 years. Many of these revisions evolved as the guidelines were used in a systematic fashion in large clinical trials and, also, with the experience following the use of newer, more effective agents, such as fludarabine.' Although this report will focus on those changes recommended by the NCI-sponsored CLL Working Group, it will include sufficient details from the original guidelines so that the reader would find it a complete document by itself without having to refer to the older version.

The most common human leukemia is B cell chronic lymphocytic leukemia (CLL), a malignancy of mature B cells with a characteristic clinical presentation but a variable clinical course. The rearranged immunoglobulin (Ig) genes of CLL cells may be either germ-line in sequence or somatically mutated. Lack of Ig mutations defined a distinctly worse prognostic group of CLL patients raising the possibility that CLL comprises two distinct diseases. Using genomic-scale gene expression profiling, we show that CLL is characterized by a common gene expression "signature," irrespective of Ig mutational status, suggesting that CLL cases share a common mechanism of transformation and/or cell of origin. Nonetheless, the expression of hundreds of other genes correlated with the Ig mutational status, including many genes that are modulated in expression during mitogenic B cell receptor signaling. These genes were used to build a CLL subtype predictor that may help in the clinical classification of patients with this disease.

The National Cancer Institute (NCI) sponsored a workshop to develop a set of standardized diagnostic and response criteria for acute myeloid leukemia (AML) clinical trials. The French-American-British (FAB) classification was retained for diagnosing AML, with the addition of patients with bone marrow morphologic features of a myelodysplastic syndrome and less than 30% bone marrow blasts, but with greater than or equal to 30% blasts in the peripheral blood. In this report, there are four important subgroups of AML not defined in the FAB classification that are discussed: undifferentiated acute leukemia, MO (AML lacking definitive myeloid differentiation by morphology or conventional cytochemistry but with ultrastructural or immunophenotypic evidence for AML), mixed lineage leukemia, and hypocellular AML. Definitions of response for clinical trials are presented to facilitate comparisons among different studies. Complete remission is considered the only response worth reporting in phase III trials, since lesser responses do not improve survival. Partial remissions may be of interest to identify active new agents in phase I and II studies. Monoclonal antibodies and cytogenetic studies are not part of the routine assessment of remission or reassessment at relapse, and their role in the evaluation of patients with AML is currently being evaluated in clinical trials. Although we recognize that some of the definitions in this report are arbitrary, generalized use of these guidelines will make results of clinical trials more comparable and interpretable.

Therapeutic resistance is a major obstacle in the treatment of acute myeloid leukemia (AML). Such resistance has been associated with rapid drug efflux mediated by the multidrug resistance gene 1 (MDR1; encoding P-glycoprotein) and more recently with expression of other novel proteins conferring multidrug resistance such as MRP1 (multidrug resistance-associated protein 1) and LRP (lung resistance protein). To determine the frequency and clinical significance of MDR1, MRP1, and LRP in younger AML patients, we developed multiparameter flow cytometric assays to quantify expression of these proteins in pretreatment leukemic blasts from 352 newly diagnosed AML patients (median age, 44 years) registered to a single clinical trial (SWOG 8600). Protein expression was further correlated with functional efflux by leukemic blasts [assessed using two substrates: Di(OC)(2) and Rhodamine 123] and with the ability of MDR-reversing agents to inhibit efflux in vitro. MDR1/P-glycoprotein expression, which was highly correlated with cyclosporine-inhibited efflux, was noted in only 35% of these younger AML patients, distinctly lower than the frequency of 71% we previously reported in AML in the elderly (Blood 89:3323, 1997). Interestingly, MDR1 expression and functional drug efflux increased with patient age, from a frequency of only 17% in patients less than 35 years old to 39% in patients aged 50 years (P =.010). In contrast, MRP1 was expressed in only 10% of cases and decreased with patient age (P =. 024). LRP was detected in 43% of cases and increased significantly with increasing white blood cell counts (P =.0015). LRP was also marginally associated with favorable cytogenetics (P =.012) and French-American-British (FAB) AML FAB subtypes (P =.013), being particularly frequent in M4/M5 cases. Only MDR1/P-glycoprotein expression and cyclosporine-inhibited efflux were significantly associated with complete remission (CR) rate (P(MDR1) =.012; P(efflux) =.039) and resistant disease (RD; P(MDR1) =.0007; P(efflux) =.0092). No such correlations were observed for MRP1 (P(CR) =.93; P(RD) =.55) or LRP (P(CR) =.50; P(RD) =.53). None of these parameters were associated with overall or relapse-free survival. Unexpectedly, a distinct and nonoverlapping phenotype was detected in 18% of these cases: cyclosporine-resistant efflux not associated with MDR1, MRP1, or LRP expression, implying the existence of other as yet undefined efflux mechanisms in AML. In summary, MDR1 is less frequent in younger AML patients, which may in part explain their better response to therapy. Neither MRP1 nor LRP are significant predictors of outcome in this patient group. Thus, inclusion of MDR1-modulators alone may benefit younger AML patients with MDR1(+) disease.