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Farnesyltransferase inhibitors (FTIs) are small-molecule inhibitors that selectively inhibit farnesylation of a number of intracellular substrate proteins such as Ras. Preclinical work has revealed their ability to effectively inhibit tumor growth in vitro and in vivo in animal models across a wide range of malignant phenotypes. Myeloid malignancies are appropriate disease targets, in that they express relevant biologic targets, such as Ras, Mitogen-Activated Protein Kinase (MAPK), AKT, and others that may depend upon farnesyl protein transferase (FTase) activity to promote proliferation and survival. Phase I trials in acute leukemias and myelodysplasia have demonstrated biologic and clinical activities as determined by target enzyme inhibition, low toxicity, and both complete and partial responses. As a result, phase II trials have been initiated in a variety of hematologic malignancies and disease settings, in order to further validate clinical activity and to identify downstream signal transduction targets that may be modified by these agents. It is anticipated that these studies will serve to define the optimal roles of FTIs in patients with hematologic malignancies and provide insight into effective methods by which to combine FTIs with other agents.

Breast cancer resistance protein (BCRP) is a novel member of the adenosine triphosphate-binding cassette superfamily of transport proteins. Transfection and enforced expression of BCRP in drug-sensitive cells confer resistance to mitoxantrone, doxorubicin, daunorubicin, and topotecan. We studied blast cells from 21 acute leukemia patients (20 acute myeloid leukemia, 1 acute lymphocytic leukemia) for the expression of BCRP mRNA using a quantitative reverse-transcription polymerase chain reaction assay. BCRP mRNA expression varied more than 1000-fold among the samples tested, with low or barely detectable expression in half of the samples. Seven samples (33%) had relatively high expression of BCRP mRNA. High expression of BCRP did not correlate strongly with high expression of P-glycoprotein, suggesting that BCRP may cause resistance to certain antileukemic drugs in P-glycoprotein-negative cases. High expression of BCRP mRNA is sufficiently frequent in AML to warrant more extensive investigations to determine the relation of disease subtype and treatment outcome to BCRP expression and function.

Several recent studies have addressed the management of infectious problems in patients with acute leukemia. Although those studies have served to emphasize the fundamental management principles formulated and proven almost 30 years ago, they have also contributed important new insights. This article describes recent developments in the management of infectious illnesses in patients who are neutropenic due to leukemia or its treatment. The discussion will focus on the increasing armamentarium of antimicrobial drugs and adjunctive agents. These expanding therapeutic options must be viewed in the context of newly emerging resistant organisms and special problems, such as the increased use of indwelling venous catheters.

Acute leukemias that arise as a result of treatment with DNA-damaging agents exhibit distinctive molecular, genetic, and clinico-pathologic features. In this timely article, the authors dissect the pathogenetic basis of therapy-related leukemias, elucidating important molecular mechanisms through which DNA damage causes these disorders. The authors also discuss how these molecular aberrations translate into specific clinical syndromes, and in addition, point out potential molecular targets for the development of innovative treatment approaches.

Chemoprevention has four goals: (1) inhibition of carcinogens, (2) logical intervention for persons at genetic risk for cancer, (3) treatment of precancerous lesions, and (4) confirmation and translation of leads from dietary epidemiology into intervention strategies. The National Cancer Institute has described a multidisciplinary, cancer science-based program for chemopreventive drug development that addresses these objectives, and has collaborated with the US Food and Drug Administration to provide consensus guidance for applying this approach. A critical component is the identification and characterization of intermediate biomarkers of cancer and their validation as surrogate end points for cancer incidence in clinical chemoprevention trials. More than 40 agents in the program are currently on the clinical development path (preclinical toxicology and phase I clinical safety studies or phase II/III efficacy trials), with the major effort in phase II studies to identify and characterize intermediate biomarkers. The continually advancing knowledge of molecular and tissue-based carcinogenesis mechanisms will provide leads to new chemopreventive agents with increased specificity for carcinogenesis-related activities and, hence, reduced toxicity by virtue of minimal effects on normal cell and tissue functions. Results from the Human Genome Project will help identify and evaluate the potential for chemopreventive intervention in cohorts at genetic risk and will provide specific target lesions for intervention strategies.

Acute myeloid leukemia (AML) developing after exposure to genotoxic agents has been recognized as a distinctive entity for more than 40 years. Secondary, or therapy-related, AML accounts for 10% to 20% of all AML cases. The basic and clinical investigation of these complex malignancies can be approached from four major vantage points: (I) dissection of the molecular structure of the induced genetic lesions and identification of the functional consequences of these changes, thereby providing clues to the pathogenesis of secondary AML and potentially serving as a basis for innovative therapeutic interventions; (2) identification and characterization of mechanisms of DNA damage and the orderly repair of such damage; (3) identification and application of accurate biomarkers of leukemogenesis for the purpose of risk prediction and quantification, potentially allowing recognition of patients especially susceptible to the leukemogenic effects of chemotherapy (for genetic or acquired reasons) and allowing their treatment for cancer to be modified based on this susceptibility; and (4) design and implementation of longitudinal clinical and genetic monitoring of high-risk populations (ie, individuals undergoing cytotoxic therapies for primary malignancies). In this article, we build on these themes, and attempt to integrate these seemingly disparate areas of research so that they can be more effectively used together to address the problem of secondary AML. Ultimately, the evaluation of these areas will inform our understanding of de novo leukemia and serve as a springboard for the development of new concepts of therapy and prevention.

AIDS-related Kaposi's sarcoma (KS) represents a complex interaction of host and viral factors. There are a number of fundamental questions surrounding the interplay between the disparate factors that can contribute to the pathogenesis and pathophysiology of this disease. Targets such as the enhancement of immune function, inhibition of angiogenic factors or immunostimulatory cytokines, inhibition of viral proteins such as Tat, or hormonal manipulations are now or will in the future become the focus of research to develop innovative anti-KS therapy and prevention measures. Antiviral approaches aimed at HIV or other viruses may potentially target a number of steps in KS pathogenesis. This article reviews diverse modalities--cytotoxic, antiviral, gene-directed, growth factor-targeted, and antiangiogenesis--that singly, or more likely in combination, stand to make an impact on the cure and prevention of AIDS-related KS.

Net overexpression or derangements of PTK-encoding oncogenes and ras serve as critical driving forces in the evolution of many epithelial and lymphohematopoietic cancers. The ability to impede signal transduction through ras-based pathways could provide a powerful molecular target for therapy and prevention of a broad spectrum of malignant neoplasms.

The empiric use of broad-spectrum antibacterial antibiotics for first fever in the granulocytopenic patient has had a major impact in lowering mortality from overwhelming infection caused by aerobic Gram-negative bacteria (Schimpff et al. 1971; Hathorn et al. 1987; Klastersky 1989; Karp et al. 1990). Despite this decrease in early infectious death, there has been an increased prevalence of Gram-positive (GP) infections in this same population which, while less life-threatening than their Gram-negative counterparts, can result in significant morbidity. Several factors are likely responsible for the emerging prominence of GP infections in this clinical setting (Table 1). In particular, the use of indwelling, multiport central venous catheters (CVC) as a routine adjunct to optimize venous access during lengthy aplasia has accentuated the problems of GP infection (Lowder et al. 1982; Lokich et al. 1985; Dickinson and Bisno 1989). Both initial catheter placement and long-term catheterization are accompanied by skin barrier invasion. The mechanical interruption of barrier integrity predisposes to local infection at exit and/or tunnel sites, thrombophlebitis, and sepsis from colonization along the entire catheter tract by common skin organisms including coagulase-negative staphylococci and Corynebacterium jeikeium. These bacteria are often resistant to beta lactam antibiotics and other antibiotics commonly used in empiric regiments for treatment of first infectious fever during aplasia (Karp et al. 1986; Anaissie et al. 1988a; Shenep et al. 1988). They are susceptible, however, to vancomycin, a cell wall-acting glycopeptide antibiotic with efficacy against both beta lactam-susceptible and resistant staphylococci and corynebacteria.

Cutaneous eruptions displaying perivascular inflammatory cell infiltrates histologically may develop with the intravenous administration of cytokines. Similar findings are seen spontaneously in some patients on recovery of peripheral blood lymphocytes after profound marrow aplasia. To investigate the production of a cutaneous perivascular infiltrate further, the ability of several cytokines to induce a perivascular lymphocytic infiltrate was studied in vitro using a skin explant model. A skin biopsy specimen obtained at the time of peripheral blood lymphocyte recovery after chemotherapy-induced marrow aplasia (n = 10) was divided and incubated for 3 days with and without a series of cytokines plus various peripheral blood mononuclear cell populations. Skin incubated with interleukin 2 and granulocyte-macrophage colony-stimulating factor induced a perivascular lymphocytic infiltrate, while control samples did not. Immunophenotypic analysis revealed that the lymphocytes were predominantly CD3+/CD4+. An infiltrate was not observed when skin was incubated with cytokines alone, without the addition of simultaneously isolated peripheral lymphocytes. A perivascular pattern was not observed with the addition of interferon gamma. Only interferon gamma induced keratinocyte intercellular adhesion molecule 1 expression in experimental tissue. Certain cytokines that affect a range of cell types are capable of inducing a common cutaneous histologic pattern, the perivascular lymphocytic infiltrate.

Patients receiving bone marrow transplants are at risk of life-threatening infections early post-transplant. This predisposition results from extensive mucosal damage and severe granulocytopenia. Common causes of infection include bacteria and fungi. Infections with opportunistic pathogens occur later and are associated with defects in cellular and/or humoral immunity. The most common sites of infections are the gastrointestinal tract, oropharynx, lung, skin and indwelling vascular catheters. Empiric approaches designed to treat common bacterial and fungal pathogens are generally effective as are measures designed to prevent dissemination of infections. These approaches are also used to prevent fungal infections.

The intravenous administration of recombinant human granulocyte-macrophage colony-stimulating factor to three patients with leukemia who were receiving marrow aplasia-inducing chemotherapy resulted in the development of wide-spread erythematous macules and papules. The course of the eruption paralleled the time of infusion of the granulocyte-macrophage colony-stimulating factor. Skin biopsy specimens taken from two of the eruptions displayed characteristic changes consisting of a variable mixture of granulocytes and lymphocytes, increased number and size of dermal macrophages, mild to moderate epidermal exocytosis, intercellular edema, and rare dyskeratotic keratinocytes. Immunophenotypic analysis of one specimen was notable for keratinocyte intercellular adhesion molecule-1 expression. Administration of the recombinant human cytokine in pharmacologic doses is postulated to induce changes in the immunologic status of the skin, resulting in the expression of a cutaneous eruption.

Human acute myelocytic leukemia (AML) marrow cells respond to stimulation with increased proliferation and enhanced intracellular metabolism of the cytotoxic antimetabolite 1-B-D arabinofuranosylcytosine (ara-C). Our previous studies have focused on the drug-induced humoral stimulatory activity (HSA) present in serum following initial cytoreduction which augments in vitro growth and biochemical pharmacology. The activity of HSA likely relates to the presence of multiple stimulators. The effect of 18-hr culture in purified recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF) (1 ng/ml) on in vitro AML marrow cell [3H]dThd incorporation into DNA, intracellular ara-C activation to the triphosphate form (ara-CTP), and subsequent ara-CTP retention were determined in leukemic cells of 11 patients and compared with cells similarly cultured in HSA-containing sera. The stimulatory effects of rhGM-CSF and HSA on both growth and pharmacologic parameters were comparable for each AML population, with maximal response to both regulators detected for FAB M2. These data demonstrate that GM-CSF acts similarly to HSA as an active stimulator of leukemic cell proliferation and net intracellular ara-C metabolism in vitro, and support clinical trials designed to examine the role of rhGM-CSF in enhancing ara-C cytotoxicity by increasing the growth fraction of drug-responsive target cells in vivo.

The patient with acute leukemia is predisposed to infection by bone marrow failure that leads to absence of granulocytes, by extramedullary leukemia infiltration that leads to barrier breakdown, and by cytotoxic antileukemia therapy that exaggerates both the hematopoietic and the tissue mucosal defects. Empiric approaches tailored to treat commonly occurring bacterial and fungal infections have successfully decreased the morbidity and mortality from overwhelming infection in these compromised patients. More recently, prophylaxis directed against dissemination of pathogens from specific sites has had a positive impact in preventing the clinical and microbiological manifestations of infection during profound aplasia. The approaches that have been successful in preventing and treating bacterial infections are being applied to the increasingly prevalent fungal infections that occur later during the granulocytopenic course, with encouraging results.

Malignant plasma cell proliferation and induced humoral stimulatory activity (HSA) occur in vivo at a predictable time following drug administration. Sequential sera from 11 patients with poor-risk multiple myeloma (MM) undergoing treatment with Cytoxan (CY) 2400 mq/sq m were assayed for their in vitro effects on malignant bone marrow plasma cell tritiated thymidine (3HTdR) incorporation. Peak HSA was detected day 9 following CY. Sequential changes in marrow malignant plasma cell 3HTdR-labeling indices (LI) paralleled changes in serum activity, with peak LI occurring at the time of peak HS. An in vitro model of chemotherapy demonstrated that malignant plasma cell proliferation was enhanced by HSA, as determined by 3HTdR incorporation assay, 3HTdR LI, and tumor cells counts, and that stimulated plasma cells were more sensitive to cytotoxic effects of adriamycin (ADR) than were cells cultured in autologous pretreatment serum. Based on these studies, we designed a clinical trial to treat 12 CY-refractory poor- risk patients with MM in which ADR (60 mg/sq m) was administered at the time of peak HSA and residual tumor cell LI (day 9) following initial CY, 2400 mg/m (CY1ADR9). Eight of 12 (67%) responded to timed sequential chemotherapy with a greater than 50% decrement in monoclonal protein marker and a median survival projected to be greater than 8 mo duration (range 4–21+ mo). These clinical results using timed sequential CY1ADR9 compare favorably with results obtained using ADR in nonsequential chemotherapeutic regimens.

Based on a series of clinical and laboratory studies of leukemia cell kinetics and responses to chemotherapy, we have developed an intensive timed-sequential regimen of daunorubicin and high-dose infusion 1-beta- D-arabinofuranosyl cytosine for the treatment of adult acute nonlymphocytic leukemia. Of the first 34 patients achieving complete remission (CR) with a single cycle of this therapy, four (12%) remain in complete remission without further therapy after a minimum of five years of follow-up. Treatment of relapsed patients with a second course of the same regimen at relapse and no chemotherapy in second remission increased to seven (21%) the number of patients expected to remain in remission for four years or more from their last chemotherapy. Beginning in 1980, however, we gave all consenting adults a second cycle of this chemotherapy in early first remission. Of the first 25 patients treated with a second cycle of this chemotherapy in early first remission, there was one toxic death, but 11 patients (44%) remain in CR with a median follow-up of almost three years.

Substances that circulate in the blood following drug-induced bone marrow aplasia produce a biphasic curve of DNA synthesis in cells in liquid and semisolid cultures which reflect relative concentrations of these growth regulators of hematopoiesis. This net effect magnified by induced marrow failure in human, rat, and mouse is a sinusoidal curve that is the reciprocal of the WBC. Generated in the bone marrow, humoral stimulating activity (HSA) produces peak growth of colonies in agar (CFU-GM) during the proliferative phase of bone marrow recovery, whereas humoral inhibitory activity (HIA), present at the time of marrow maturation, suppresses colony growth. Split femurs from rats given cyclophosphamide (CY) and killed at regular intervals condition media that affect DNA synthesis in a fashion similar to that of HSA-HIA in the rats' sera. In Dexter cultures, HSA is derived from the adherent rather than the hematopoietic cell, whereas HIA is produced by that nonadherent cell. Animals treated with a lethal dose of busulfan (BU) produce large amounts of HSA in vivo until death. Those transplanted with adherent bone marrow cells depleted of hematopoietic cells on day 1 after BU also die, whereas those given nonadherent marrow cells survive and generate HIA at the time of bone marrow recovery. HSA and media conditioned by bone marrow stromal cells causes an increase in spleen colonies (CFU-S), as does HIA. These studies support the contention that the net effect of putative regulators of hematopoiesis, measured in the drug-perturbed state, consist of a constantly present stimulator emanating from bone marrow stroma, and a variable inhibitor produced by maturing hematopoietic bone marrow cells.

To define the relationship between leukemic cell growth, intracellular metabolism of 1-B-D-arabinofuranosylcytosine (ara-C), and the clinical response to timed sequential induction therapy with ara-C in adult acute myelogenous leukemia (AML), growth kinetic and biochemical pharmacologic determinants were examined in AML bone marrow populations. Leukemic blasts from 45 previously untreated patients obtained prior to therapy were cultured in vitro in autologous pretreatment serum (APS) and in serum containing drug-induced humoral stimulatory activity (HSA). Cell populations cultured in HSA demonstrated both increased proliferation, as measured by both [3H]dThd incorporation into DNA and [3H]dThd leukemic blast labeling index, and greater [3H] ara-C leukemic blast labeling index relative to cells maintained in APS. HSA-cultured marrow cells from the 31 patients who achieved complete remission with ara-C-containing therapy demonstrated enhanced intracellular formation of ara-C 5′-triphosphate over three hours and retention of this active form during one subsequent hour in drug-free medium relative to cells maintained in APS. In contrast, cells from the 14 nonresponsive patients demonstrated no such HSA- induced increases in intracellular ara-C metabolism. These studies of human AML marrow cells identify behavior patterns of ara-C activation and net metabolism in the kinetically perturbed, proliferative state that may discriminate clinical sensitivity from clinical resistance to ara-C-based timed sequential therapy. Sensitive AML populations behave similarly to normal hematopoietic cohorts, with direct linkage of HSA- perturbed growth and pharmacologic parameters, while refractory cells demonstrate uncoupling of these determinants in the growth-stimulated state. These in vitro measurements may further serve as a template for prediction of clinical outcome to timed sequential therapy with ara-C, where both pharmacologic and cytokinetic determinants of response are intrinsic to the success of the designed drug scheduling.

Acute leukemia is a heterogeneous tumor with respect to cellular proliferation and is sensitive to positive and negative growth control factors. Tumor associated inhibitory activity (TAIA) and simultaneously present humoral stimulatory activity (HSA) in this disease may be modulated by timed sequential chemotherapy to increase tumor growth at a predictable time and make it more sensitive to accurately administered drug. Our in vivo studies of timed sequential chemotherapy in human leukemia demonstrate than an increase in tumor labeling index (LI) temporally coincides with the detection of HSA following drug administration. Maximal HSA occurs at a predictable time following initial administration of the aplasia-producing drug and is coincident with an increased LI of recovering normal marrow granulocytic elements and marrow tumor cells. These studies demonstrate the salutary effect of drugs given in high dose to reduce tumor mass and recruit tumor cells to further high-dose drug sensitivity.

The authors examined 117 consecutive patients with acute leukemia within a few days of diagnosis. Sixty-six patients had acute nonlymphocytic leukemia, and 51 had acute lymphocytic leukemia. Forty-two percent of the patients had abnormal ocular findings related to leukemia. The authors found an association between the presence of intraretinal hemorrhages and thrombocytopenia for all patients. In addition, patients with acute lymphocytic leukemia and intraretinal hemorrhages had lower hematocrit levels than did those without such hemorrhage. The presence of anemia was related to the findings of white-centered hemorrhages in patients with acute nonlymphocytic leukemia. The presence of cotton-wool spots was not associated with hematologic parameters. Intraretinal hemorrhages, white-centered hemorrhages, and cotton-wool spots were all found more frequently in adults than in children.

Factors that influence the proliferation of marrow elements can be detected in sera. To determine the function and to compare the effect of these factors, cells were obtained from patients with normal and leukemic bone marrows. The effects of drug-induced stimulatory and inhibitory sera and leukemic pretreatment sera over time (0 to 6 days) on proliferation and granulocytic morphology of normal and leukemic bone marrow cells in culture were evaluated. Increased proliferation was associated with stimulatory sera, while inhibitory and leukemic pretreatment sera retarded proliferation of both normal and malignant cells. Exposure of normal proliferative cells to inhibitory or leukemic pretreatment sera yielded the greatest increase in mature granulocyte forms. In contrast, although the proliferative response of leukemic cells to these sera was similar to normal, maturation was minimal. These data suggest that leukemic pretreatment sera are similar to inhibitory sera and are not leukemogenic. Both retard proliferation of normal and leukemic bone marrow cells while enhancing maturation of normal cells. Leukemic myeloblasts, however, cannot be made to mature by these humoral regulators.

Patients undergoing intensive antileukemic chemotherapy and profound granulocytopenia are susceptible to overwhelming infections, particularly those arising from disease- and therapy-related gastrointestinal tract damage. We have previously demonstrated that the ability to suppress bacterial colonization of this site with oral norfloxacin prophylaxis (400 mg every 12 h) affects the incidence and distribution of aerobic gram-negative bacterial infections and the overall management of infectious complications in this patient population. We have now determined the broad impact of continuous, long-term use of oral norfloxacin on aerobic gram-negative bacterial infection and colonization, overall management of presumed and documented infections during marrow aplasia and emergence of clinically significant antibiotic resistant pathogens during intensive antileukemic chemotherapy. Oral norfloxacin prophylaxis administered throughout the course of induced granulocytopenia continues to afford effective protection by suppressing the development of aerobic gram-negative infections, particularly those arising from the gastrointestinal tract, and preventing the acquisition or emergence of multiply resistant pathogens. A long-range effect of norfloxacin on pathogens colonizing the respiratory tract is also detected, with inhibition of acquired drug resistance occurring at that site as well. For these reasons, norfloxacin continues to be an excellent agent for oral prophylactic use in this patient population.

Most studies using high-dose cytarabine (ara-c) for the therapy of acute leukemia have employed intermittent short infusions. In this study, we have evaluated the pharmacology and toxicity of high-dose ara-c by 72-hour continuous infusion. Plasma ara-c concentrations varied from 3.6 microM at the starting dose of 4 g/m2/72 hours to 22.6 microM at 18 g. Plasma clearance appeared to decrease progressively at doses greater than 10 g, suggesting that the route of elimination was saturable. CSF ara-c concentrations ranged from 1.2 microM at 4 g to 4.1 microM at 18 g; the ratio of CSF to plasma ara-c decreased progressively from 0.33 at 4 g to 0.18 at 18 g. The toxic effects were significant and included myelosuppression, nausea, and vomiting in all patients. No single dose-limiting toxicity was identified. Further dose escalation was precluded by combined organ system effects, which included hepatic, pulmonary, renal, and gastrointestinal toxic effects. Attempts to incorporate a 72-hour infusion of ara-c into a combination chemotherapy regimen should proceed cautiously with a starting dose of 6 g/m2/72 hours.

To define the relationship between perturbed cell growth and intracellular metabolism of 1-beta-D-arabinofuranosylcytosine (ara-C) in sensitive human cells, growth kinetic, and biochemical pharmacological determinants were examined in normal human bone marrow populations in vitro in normal serum and in the presence of drug-induced humoral stimulatory activity (HSA). Cells cultured in HSA demonstrated both increased proliferation and greater ara-C-related inhibition of DNA synthesis than did cells maintained in normal serum, as measured by [3H]thymidine incorporation into DNA and [3H]thymidine granulocyte precursor labeling index. Parallel measurements of [3H]ara-C incorporation into DNA demonstrated similar behavior in HSA-perturbed cells. When these cultured cells were exposed to 1 and 10 microM ara-C, intracellular formation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate over 3 hr and retention of this active form during 1 subsequent hr in drug-free medium were both increased in HSA-stimulated cells relative to cells cultured in normal serum. These studies demonstrate coupling of induced cell growth kinetics with enhanced intracellular metabolism of the S-phase-specific antimetabolite ara-C in normal human marrow cells. The close direct relationship between growth kinetic perturbation and augmentation of intracellular ara-C activation in this normal hematopoietic model provides a basis for comparison with leukemic cell populations, in which uncoupling of growth kinetics and pharmacokinetics may signify divergence from normal drug-sensitive cell behavior and, thus, resistance to ara-C cytotoxicity.

Over 80 percent of patients with invasive pulmonary aspergillosis (IPA) undergoing intensive antileukemic chemotherapy in a recent two-year period survived the pulmonary infection as a result of early diagnosis and aggressive therapy with high-dose amphotericin B and 5-fluorocytosine. CT played an important role in establishing the early diagnosis of IPA and affected management. Since our original communication describing the CT findings of IPA, we have added ten new cases, each subsequently substantiated by lung biopsy (two), autopsy (two), and/or positive cultures of sputum or extrapulmonary sites (seven). The CT halo sign, or zone of lower attenuation surrounding a pulmonary mass, was present in eight of nine patients with early CT scans obtained during bone marrow aplasia. Characteristic CT progression from multiple fluffy masses to cavitation or air crescent formation suggested IPA in five of seven patients with serial CT scans. CT directly affected patient management in seven of ten cases. Scan findings were one criterion for increasing to high-dose amphotericin B or for adding 5-fluorocytosine. CT characteristics of healing IPA lesions were similar to resolving pulmonary infarcts and were used to monitor disease activity in patients on long-term amphotericin B and prior to retreatment chemotherapy.

Eighteen patients referred to The Johns Hopkins Oncology Center for treatment of acute myelocytic leukemia during a 2-year period had pretreatment wbc counts greater than 50,000/microliter. Despite immediate admission, aggressive supportive care, and rapid institution of chemotherapy, six patients died from complications of the high wbc count at presentation. The patients who died had significantly higher initial wbc counts, lower platelet counts, and lower arterial oxygen saturation; they were older, more likely to be female, and more likely to have abnormal serum urea nitrogen than the 12 patients who survived. Five of the six patients who died had experienced a delay of greater than 48 hours from diagnosis to referral, and only one of the 12 patients who survived was not promptly referred for treatment at the time of diagnosis (P = 0.004). A mathematical model, the logit of the fraction of the initial wbc count versus the logarithm of time after starting therapy, was used to describe the response of the wbc count to chemotherapy. This logit analysis reduced the data for individual patients to a linear function, permitting statistical description of the population as a whole. This statistical description makes possible the comparison of different approaches to lowering the wbc count in such patients and the correlation of rate of response of wbc count with the probability of achieving remission and with duration of remission.

Studies were conducted in the leukemic mouse and rat to test the hypothesis that enhanced effects of drugs given in sequence relate to a predictable increase in tumor growth and sensitivity to cycle-active agents. The rationale is based on a) evidence that, following drug-induced aplasia, resultant bone marrow proliferation in vivo corresponds temporally with induced humoral stimulatory activity, and on b) models that demonstrate increased cytotoxicity of beta-cytosine arabinoside (Ara-C) to myeloblasts cultured in humoral stimulatory activity (HSA). CD2F1 mice bearing L-1210 leukemia received a course of 60 mg Ara-C/kg every 8th hour (q.8 h) three times on day 0 and on another day in sequence (0,1 through 0,7). The longest survival (250% of controls) was in animals whose second course began on day 3, the time of peak HSA as measured by DNA synthesis induced in L-1210 cells in culture. LBN rats bearing acute myelocytic leukemia (AML) were treated with 100 mg Ara-C/kg q.8 h six times beginning on day 0 and on other days in sequence (0,1 through 0,12). The longest survival was in those treated on day 0,6 (760% of controls), the time of peak serum stimulation, and tumor labeling index (LI). Thirty-seven patients with AML received a single course of therapy with 45 mg Ara-C/kg by a 72-hour infusion and 1.0 mg daunorubicin/kg every day three times. On day 8, the time of peak HSA and tumor LI, Ara-C was again infused. Complete remission was achieved in 56% (65% of all patients less than 60 yr old) with a single cycle of therapy. Median duration of chemotherapy-free remission was 10 months. Of 11 relapsing patients, 8 achieved a second remission with the same regimen. These studies demonstrated that the amount of proliferation of residual tumor and thereby sensitivity to cycle-active drugs given in sequence relates to the initial drug effect on tumor proliferation and the induction of humoral stimulation.

Thirty-one cases of acute leukemia with blast cells greater than or equal to 70% positive for the hematopoietic stem cell Ag, CD34 (MY10, HPCA-1), were identified from the University of Nebraska Medical Center and The Johns Hopkins Oncology Center over an 18-month period. Fourteen of the cases were classified as early B-lineage ALL, 3 cases were other ALL subtypes, and 14 of the cases were ANLL. Five of the 17 cases of ALL expressed one or more myeloid-associated surface Ags, 3 ANLL cases expressed CD10 (CALLA, J5), and T-lymphoid Ags were present in 12 of 31 cases (1 T-cell ALL, 3 of 16 B-lineage ALL cases, and 8 of 14 ANLL cases). Eleven of 12 CD34+ ALL cases studied had abnormal karyotypes; only 7 of 12 CD34+ ANLL cases studied had abnormal karyotypes, and 3 of these were CD10+ ANLL. Six cases were Ph1 positive, including the one mature B cell ALL, 4 early B-lineage ALL, and 1 CD10+ ANLL case. Good and poor prognosis subgroups of high frequency of expression of CD34 leukemias could be identified, generally, as would have been predicted by previously defined criteria. Thus, of the 10 Ph1-negative early B-lineage ALL patients, 9 achieved CR (90%). At the other extreme, the CR rate of CD10- ANLL was 4 of 11 (36%). The leukemias characterized by greater than or equal to 70% of cells positive for CD34 form a relatively undifferentiated subset of the leukemias which may show features associated with more than one lineage, and if CD10- and myeloid morphology, may respond poorly to therapy.

Clinical trials with laboratory correlates were conducted in patients with acute leukemia to determine if relationships exist between drug dose and growth of surviving leukemia cells. The therapeutic design was based on findings in the leukemic rat that relate the initial dose of drug and tumor kill to the magnitude of residual tumor proliferation and sensitivity to a second drug. Patients with acute myelocytic leukemia received cytarabine, either 2 or 6 g/m2/72 h by continuous infusion. The presence and magnitude of change between initial and residual tumor after treatment, as measured by change in labeling indices, depended on the "priming" dose of drug. The amount of perturbation correlated with clinical response to cytarabine given at the time of induced proliferation. With results which parallel the rat data, the direct relationship of initial drug dose and proliferation of residual tumor is demonstrated in humans, and lends support to the design of our clinical trials of timed sequential therapy.

A cure rate can be obtained with intensive cytoreductive treatment given to a subset of patients with acute myelocytic leukemia in bone marrow remission. This report updates our experience with postremission timed sequential therapy using cytarabine and daunorubicin (Ac-D-Ac) and compares it with other brief, aggressive strategies including bone marrow transplantation. The median disease-free survival (DFS) of all patients treated in remission is 2.5 years with a greater than 40% probability of DFS at 8 years. These results are similar to those achieved with bone marrow-ablative and other intensive but nonablative treatment plans.