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Biomedical subjects

C H Pui

Publications and source records attributed to C H Pui.

At least 109 records · Page 6Linked to original sources
PubMed1997

Prevalence and growth characteristics of malignant stem cells in B-lineage acute lymphoblastic leukemia.

We used a stroma-supported culture method to study the prevalence and growth characteristics of malignant stem cells in acute lymphoblastic leukemia (ALL). In 51 of 108 B-lineage ALL samples, bone marrow-derived stroma not only inhibited apoptosis of ALL cells but also supported their proliferation in serum-free medium. When single leukemic cells were placed in the stroma-coated wells of microtiter plates, the percentage of wells with leukemic cell growth after 2 to 5 months of culture ranged from 6% to 20% (median, 15%; 5 experiments). The immunophenotypes and genetic features of cells recovered from these cultures were identical to those noted before culture. All cells maintained their stroma dependency and self-renewal capacity. Leukemic clones derived from single cells contained approximately 10(3) to 10(6) cells after 1 month of culture; other clones became detectable only after prolonged culture. Cell growth in stroma-coated wells correlated with the number of initially seeded cells (1 or 10; r = .87). However, the observed percentages of positive wells seeded with 10 cells always exceeded values predicted from results with single-cell-initiated cultures (P < .003 by paired t-test), suggesting stimulation of leukemic cell growth by paracrine factors. In conclusion, the proportion of ALL cells with clonogenic potential may be considerably higher than previously thought.

Adipose Tissue↗
PubMed1997

Molecular diagnosis of thiopurine S-methyltransferase deficiency: genetic basis for azathioprine and mercaptopurine intolerance.

BACKGROUND: Thiopurine S-methyltransferase (TPMT) catalyzes the S-methylation (that is, inactivation) of mercaptopurine, azathioprine, and thioguanine and exhibits genetic polymorphism. About 10% of patients have intermediate TPMT activity because of heterozygosity, and about 1 in 300 inherit TPMT deficiency as an autosomal recessive trait. If they receive standard doses of thiopurine medications (for example, 75 mg/m2 body surface area per day), TPMT-deficient patients accumulate excessive thioguanine nucleotides in hematopoietic tissues, which leads to severe and possibly fatal myelosuppression. OBJECTIVE: To elucidate the genetic basis and develop molecular methods for the diagnosis of TPMT deficiency and heterozygosity. DESIGN: Diagnostic test evaluation. SETTING: Research hospital. PATIENTS: The TPMT phenotype was determined in 282 unrelated white persons, and TPMT genotype was determined in all persons who had intermediate TPMT activity (heterozygotes) and a randomly selected, equal number of persons who had high activity. In addition, genotype was determined in 6 TPMT-deficient patients. MEASUREMENTS: Polymerase chain reaction (PCR) assays were developed to detect the G238C transversion in TPMT*2 and the G460A and A719G transitions in TPMT*3 alleles. Radiochemical assay was used to measure TPMT activity. Mutations of TPMT were identified in genomic DNA, and the concordance of TPMT genotype and phenotype was determined. RESULTS: 21 patients who had a heterozygous phenotype were identified (7.4% of sample [95% CI, 4.7% to 11.2%]). TPMT*3A was the most prevalent mutant allele (18 of 21 mutant alleles in heterozygotes; 85%); TPMT*2 and TPMT*3C were more rare (about 5% each). All 6 patients who had TPMT deficiency had two mutant alleles, 20 of 21 patients (95% [CI, 76% to 99.9%]) who had intermediate TPMT activity had one mutant allele, and 21 of 21 patients (100% [CI, 83% to 100%]) who had high activity had no known TPMT mutation. Detection of TPMT mutations in genomic DNA by PCR coincided perfectly with genotypes detected by complementary DNA sequencing. CONCLUSIONS: The major inactivating mutations at the human TPMT locus have been identified and can be reliably detected by PCR-based methods, which show an excellent concordance between genotype and phenotype. The detection of TPMT mutations provides a molecular diagnostic method for prospectively identifying TPMT-deficient and heterozygous patients.

Azathioprine↗
PubMed1997

Higher frequency of glutathione S-transferase deletions in black children with acute lymphoblastic leukemia.

The genetic polymorphisms in human glutathione S-transferases (GST) M1 and T1 have been associated with race, disease risk, and outcome of some adult cancers. Also, there are racial differences in the incidence and characteristics of childhood acute lymphoblastic leukemia (ALL). Our objectives were to compare the frequency of the null genotype for GSTM1, GSTT1, or both in children with ALL to that in healthy controls, and to determine whether GST genotype was associated with treatment outcome and prognostic factors. We studied GSTM1 and GSTT1 genotypes in somatic cell DNA from black children and white children with ALL and in 416 healthy controls, using a polymerase chain reaction technique. Ninety of 163 (55.2%) white ALL patients and 14 of 34 (41.2%) black patients were GSTM1 null, frequencies not significantly different (P = .19) than healthy controls (53.5% in whites and 27.6% in blacks), although there was a trend toward more null genotypes in black ALL patients. Twenty-three of 163 (14.1%) white ALL patients and 12 of 34 (35.3%) black ALL patients were GSTT1 null, not different (P = .34) than the frequencies in healthy controls (15.0% in whites and 24.1% in blacks). However, the frequency of the "double-null" genotype, lacking both GSTM1 and GSTT1, was higher in black patients with ALL (8 of 34 or 23.5%) than in black controls (3.9%) (P = .0005), but this was not the case in white patients with ALL (10 of 163 or 6.1%) compared to white controls (8.0%) (P = .68). In stratified analyses, the GST double-null genotype was not associated with other characteristics that might differ between whites and blacks with ALL, such as age, T-lineage immunophenotype, presenting white blood cell count, DNA index, or insurance status. The null genotype for GSTM1, GSTT1, or both was not found to be a prognostic factor for disease-free survival or probability of hematologic remission; central nervous system relapse tended to be less common in those with the GSTM1 null genotype (P = .054). The double-null genotype for GSTM1 and GSTT1 is more common among blacks but not whites with childhood ALL. These data suggest that GST genotype, coupled with unidentified additional risk factors, may play a role in risk of childhood ALL in American blacks.

Adult↗
PubMed1997

Case-control study suggests a favorable impact of TEL rearrangement in patients with B-lineage acute lymphoblastic leukemia treated with antimetabolite-based therapy: a Pediatric Oncology Group study.

TEL gene rearrangement is the most common genetic lesion in pediatric acute lymphoblastic leukemia (ALL), occurring in about 25% of B-lineage cases. We previously showed that, among patients treated on St Jude protocols, TEL rearrangement independently conferred an excellent prognosis. To extend these results to patients treated with antimetabolite-based therapy, we performed Southern blot analysis to determine the TEL gene status of 104 cases of B-lineage ALL treated on Pediatric Oncology Group 8602, matched on age, gender, and leukocyte count. There were 52 failures among the 77 patients with germline TEL, compared with only 8 failures among 27 patients in the rearranged group. Based on a two-sided logistic regression analysis, stratified for age (subdivided at 10 years), leukocyte count (subdivided at 50,000), and gender, the estimated odds of failing by 4 years in the germline TEL group is 5.4 times that of the rearranged TEL group, with 95% confidence from 1.9 to 15.6, two-sided P = .0009. Thus, the presence of a rearranged TEL gene is also associated with an improved survival among patients treated with antimetabolite-based therapy. Our results indicate that all newly diagnosed ALL patients should be screened for TEL gene rearrangements and suggest that these patients are candidates for less intensive therapy.

Antimetabolites, Antineoplastic↗
PubMed1997

XYY syndrome in children with acute lymphoblastic leukemia.

Certain constitutional chromosomal abnormalities increase the risk of malignancy and/or decrease treatment tolerance. We identified two patients with the XYY syndrome among a total of 444 male children with acute lymphoblastic leukemia who had complete cytogenetics studies. In both cases, the leukemic cell karyotype suggested a constitutional XYY abnormality that was confirmed in studies of lymphocytes obtained during remission. The incidence rate in our series is higher than that of the XYY syndrome in the general population (0.0045 vs. 0.001), but not significantly so. This finding and a literature review failed to confirm an increased frequency of the XYY syndrome among children with acute lymphoblastic leukemia. Both of our patients remain in remission 24 and 28 months, respectively, postdiagnosis. Their tolerance of intensive treatment, including high-dose methotrexate, suggests that the untoward treatment toxicity seen in patients with chromosomal abnormalities such as trisomy 21 does not extend to the XYY syndrome.

Adolescent↗
PubMed1997

Systemic hemophagocytosis masking the diagnosis of large cell non-Hodgkin lymphoma.

An 11-year-old female presented with clinical features suggestive of malignant histiocytosis: fever, weight loss, subcutaneous nodules, pulmonary infiltrates, adenopathy, and hepato-splenomegaly. On biopsy, lymph node and bone marrow demonstrated necrosis and extensive hemophagocytosis with no definitive evidence of malignancy: the subcutaneous nodules, however, demonstrated large-cell non-Hodgkin lymphoma. This clinicopathologic picture has been reported in adults, but not in children. Although serum G-CSF, M-CSF, and TNF levels were not elevated in this child, it is possible that other cytokines induced either directly or indirectly by the subcutaneous lymphoma resulted in hemophagocytosis.

Bone Marrow↗
PubMed1997

Acute lymphoblastic leukemia.

Advances in the molecular and immunologic characterization of leukemic cells have greatly aided the diagnosis and risk assignment of ALL, as well as the monitoring of bone marrow samples for minimal residual disease. Currently, 75% of childhood cases have biologically and therapeutically relevant genetic abnormalities. Although gene discoveries in ALL have not been directly translated into effective therapy, there is every reason to believe that this disease will eventually yield to molecular intervention. In the meantime, efforts are being made to enhance the efficacy of existing regimens while reducing their toxic side effects. We have learned, for example, the following: high-dose methotrexate is more effective than lower-dose methotrexate, especially for T-cell ALL; patients who need drastic adjustment of mercaptopurine dosage due to thiopurine S-methyltransferase deficiency can be prospectively identified; dexrazoxane (ICRF-187) could reduce anthracycline cardiotoxicity; granulocyte colony-stimulating factor can shorten hospital stays for febrile neutropenia after intensive remission induction therapy; and prolonged low-dose epipodophyllotoxin treatment may reduce the risk of therapy-induced acute myeloid leukemia without compromising treatment efficacy. The challenge now is to identify specific treatments for genetically defined subtypes of ALL.

Child↗
PubMed1997

Predominance and characteristics of Burkitt lymphoma among children with non-Hodgkin lymphoma in northeastern Brazil.

The purpose of this paper was to define the histologic distribution, clinical features, and treatment response of childhood non-Hodgkin lymphoma (NHL) in northeastern Brazil. We reviewed medical records and histopathologic studies of 98 children treated for NHL from 1980 to 1987 at a major pediatric cancer center in Recife, Brazil. Treatment outcome was evaluated in relation to tumor burden (stage and serum LDH) and type of therapy (LSA2L2 vs other multiagent chemotherapy). There was a striking predominance of the small noncleaved cell (Burkitt) subtype, which occurred in 92 of the 98 children and adolescents diagnosed with NHL. Subsequent analyses focused on these patients. The majority (n = 84) had advanced (stage III/IV) disease at diagnosis. The abdomen was the most common site of disease (84 cases); jaw involvement was rare (three cases). Five-year event-free survival (excluding treatment refusals) was significantly better for patients with limited vs advanced stage disease (75 +/- 14% vs 42 +/- 6%; P < 0.04). Elevated serum LDH (>500 U/l) was associated with a poorer outcome (P = 0.008). The type of chemotherapy did not affect EFS (P = 0.95). Only 39% of patients are long-term survivors, reflecting the high rate of septic deaths (25% of patients) and parental refusal/abandonment of therapy (10%). Epstein-Barr virus (EBV) was detected in tumor cells from eight of the 11 cases studied. In clinical presentation, these cases resemble sporadic Burkitt lymphoma, yet in their apparent responsiveness to LSA2L2 therapy and association with EBV, they do not. Childhood NHL in northeastern Brazil is predominantly of the Burkitt subtype, and is associated with clinical features that appear to distinguish it from the endemic and sporadic forms of this tumor. These cases may represent a third or intermediate subtype of Burkitt lymphoma.

Adolescent↗
PubMed1997

Philadelphia chromosome-positive acute lymphoblastic leukemia in children: durable responses to chemotherapy associated with low initial white blood cell counts.

To substantiate the reported sensitivity of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) to St Jude-type multiagent chemotherapy and to identify means of selecting patients most likely to benefit from such treatment, we analyzed the clinical and biologic characteristics of 12 patients with classic Ph+ ALL who were treated in either of two total therapy programs at St Jude Children's Research Hospital (1989-1994). Event-free survival estimates for this cohort were compared with historical data on 11 patients from an earlier total therapy study (Lancet 1994; 343: 331-332). The prognostic importance of age, white blood cell count and other presenting features was assessed by the logrank test in all 23 patients. Complete remissions were induced in 92% of the patients treated since 1989, compared with 82% of the historical control group (P > 0.05). There was essentially no difference in event-free survival between the study group and historical controls (4-year Kaplan-Meier estimates, 33 +/- 19% s.e. vs 36 +/- 13%). Further analysis of potentially informative risk factors identified a good-prognosis subgroup defined by an initial white blood cell count of < or =25 x 10(9)/l and a 4-year event-free survival of 73 +/- 19%. In conclusion, intensive multiagent chemotherapy offers an attractive therapeutic option for children and adolescents with Ph+ ALL and low presenting leukocyte count.

Adolescent↗
PubMed1997

Genetic studies of childhood acute lymphoblastic leukemia with emphasis on p16, MLL, and ETV6 gene abnormalities: results of St Jude Total Therapy Study XII.

To determine the frequency and prognostic significance of recently described genetic lesions in pediatric acute lymphoblastic leukemia (ALL), all cases with available leukemic cell samples treated on St Jude Study XII were analyzed by molecular techniques for alterations of the p16, MLL and ETV6 genes. Homozygous p16 deletion was seen in 36 of 155 cases, including 14 of 23 T cell cases, but had no prognostic value. Rearrangement of MLL was seen in nine of 170 cases (5%) and conferred a poor prognosis, with a 5-year EFS estimate of only 11 +/- 7%, compared with 74 +/- 5% for the germline MLL group (P=0.0001). By contrast, rearrangement of ETV6 was found in 35 cases (21%) and was significantly associated with a better outcome (5-year EFS estimates: 87 +/- 7% vs 64 +/- 6%). In a Cox regression model adjusted for age, DNA index, race, leukocyte count, treatment group, and CNS status, ETV6 rearrangement retained independent prognostic significance (two-sided P value 0.012). Thus, in this uniformly treated group of patients, we confirmed the unfavorable prognostic significance of MLL rearrangement and demonstrated the favorable impact of ETV6 rearrangement, suggesting that these factors be added to ALL risk classification schemes.

Carrier Proteins↗
PubMed1997

Urate oxidase in prevention and treatment of hyperuricemia associated with lymphoid malignancies.

Standard prophylaxis and treatment of malignancy-associated hyperuricemia in the USA has been allopurinol with vigorous hydration, urinary alkalinization and osmotic diuresis. Urate oxidase, the enzyme that converts uric acid to allantoin (a readily excreted metabolite that has 5- to 10-fold higher solubility than uric acid), is an alternative therapy; however, few published findings support this practice. Between February 1994 and December 1996, we administered non-recombinant urate oxidase (Uricozyme) to 126 children with newly diagnosed non-B cell acute lymphoblastic leukemia (ALL) during the first 5 days of chemotherapy with methotrexate, 6-mercaptopurine or both. Their blood levels of uric acid and other indicators of tumor lysis were measured at diagnosis and during treatment and then compared with findings in 129 similarly treated historical controls who had received allopurinol to control hyperuricemia. Clinical responses to urate oxidase were also determined in eight patients with newly diagnosed B cell ALL or advanced-stage non-Hodgkin lymphoma. Patients treated with urate oxidase had rapid and significantly greater decreases in their blood uric acid levels than did the historical controls (median maximal level during treatment, 2.3 vs 3.9 mg/dl, P < 0.001). They also had lower creatinine (0.6 vs 0.7 mg/dl, P = 0.01) and blood urea nitrogen (11 vs 24 mg/dl, P < 0.001) levels. Similar findings were made in the eight cases of B cell ALL or non-Hodgkin lymphoma. None of the patients required dialysis for acute renal failure. Six (4.5%) of the 134 children given urate oxidase had allergic reactions, manifested primarily by urticaria, bronchospasm and hypoxemia. Thus, non-recombinant urate oxidase is a more effective uricolytic agent than allopurinol but is associated with acute hypersensitivity reactions, even in patients without a history of allergy.

Allopurinol↗
PubMed1997

Recent advances in the biology and treatment of childhood acute lymphoblastic leukemia.

The molecular analysis of genetic alterations in acute lymphoblastic leukemia has led to the development of molecular diagnostic techniques that have improved the biologic characterization of newly diagnosed patients. Modern treatment protocols rely on this information to tailor the intensity of therapy to the risk of relapse. For example, the TEL-AML1 fusion, the most common genetic abnormality in childhood acute lymphoblastic leukemia, was recently shown to be an independent, favorable prognostic factor, suggesting that patients with this abnormality are best treated with conventional antimetabolite-based therapy. Extremely high-risk patients, such as those with MLL gene rearrangements, are now considered candidates for alternative treatments, such as allogeneic bone marrow transplantation in first remission. Efforts are currently being made to reduce the long-term sequelae of therapy and to use molecular techniques to monitor minimal residual disease.

Child↗
PubMed1997

Differences in folylpolyglutamate synthetase and dihydrofolate reductase expression in human B-lineage versus T-lineage leukemic lymphoblasts: mechanisms for lineage differences in methotrexate polyglutamylation and cytotoxicity.

Cellular accumulation of methotrexate polyglutamates (MTXPGs) is recognized as an important determinant of the cytotoxicity and selectivity of methotrexate in acute lymphoblastic leukemia (ALL). We identified a significantly lower cellular accumulation of MTXPGs in T-lineage versus B-lineage lymphoblasts in children with ALL, which is consistent with the worse prognosis of T-lineage ALL when treated with conventional antimetabolite-based therapy. Maximum MTXPG accumulation in leukemic blasts in vivo was 3-fold greater in lymphoblasts of children with B-lineage ALL (129 children) compared with those with T-lineage ALL (20 children) (p < 0.01) and was characterized by a saturable (Emax) model in both groups. The human leukemia cell lines NALM6 (B-lineage) and CCRF/CEM (T-lineage) were used to assess potential mechanisms for these lineage differences in MTX accumulation, revealing i) greater total and long-chain MTXPG accumulation in NALM6 over a wide range of methotrexate concentrations (0.2-100 microM), ii) saturation of MTXPG accumulation in both cell lines, with a higher maximum (Emax in NALM6, iii) 3-fold higher constitutive FPGS mRNA expression and enzyme activity in NALM6 cells, iv) 2-fold lower levels of DHFR mRNA and protein in NALM6 cells, and v) 4-6 fold lower extracellular MTX concentration and 2-fold lower intracellular MTXPG concentration to produce equivalent cytotoxicity (LC50) in NALM6 versus CEM. There was a significant relationship between FPGS mRNA and enzyme activity in lymphoblasts from children with newly diagnosed ALL, and blast FPGS mRNA and activity increased after methotrexate treatment. These data indicate higher FPGS and lower DHFR levels as potential mechanisms contributing to greater MTXPG accumulation and cytotoxicity in B-lineage lymphoblasts.

Antimetabolites, Antineoplastic↗
PubMed1997

TEL gene rearrangement in acute lymphoblastic leukemia: a new genetic marker with prognostic significance.

PURPOSE: TEL gene rearrangements due to the 12;21 chromosomal translocation are the most common molecular genetic abnormality in childhood acute lymphoblastic leukemia (ALL), occurring in approximately 25% of cases with a B-precursor immunophenotype. The limited number of clinically useful genetic markers in this leukemia subtype prompted us to assess TEL status as a predictor of treatment outcome. PATIENTS AND METHODS: We determined the status of the TEL gene (rearranged or germline) in 188 cases of B-precursor acute leukemia using Southern blot analysis and related the findings to event-free survival. All comparisons of outcome were stratified by treatment regimen, risk classification, age, and leukocyte count. RESULTS: Forty-eight patients (26%) had a rearranged TEL gene. At 5 years of follow-up, an estimated 91% +/- 5% (SE) of this group were event-free survivors, compared with only 65% +/- 5% of the group with germline TEL (stratified log-rank P = .011). For nonhyperdiploid patients, the odds ratio of an adverse event in the germline TEL group to that for the rearranged TEL group was 4.06 (95% confidence interval, 1.86 to 8.84). The relationship of TEL rearrangement to a favorable prognosis was independent of recognized good-risk features in B-precursor leukemia, including age, initial leukocyte count, and hyperdiploidy. CONCLUSION: Rearrangement of the TEL gene distinguishes a large subset of children with favorable-prognosis B-precursor leukemia who cannot be identified by standard prognostic features. It may be possible to treat these patients less aggressively without loss of therapeutic efficacy.

Child↗
PubMed1997

Late mortality of long-term survivors of childhood cancer.

PURPOSE: To determine the frequency and patterns of late mortality among long-term survivors of childhood cancer. MATERIALS AND METHODS: Medical records of patients who survived at least 5 years after the diagnosis of childhood cancer were reviewed to determine the causes of subsequent deaths. Estimated 15-year survival and standardized mortality ratios for deaths from nonneoplastic treatment complications were compared with adjusted United States population estimates. The study included 2,053 patients who had survived > or = 5 years, grouped by treatment eras that reflected increased intensity of therapy and significantly improved survival (early era, 1962 to 1970; recent era, 1971 to 1983). RESULTS: There have been 258 subsequent deaths in the 2,053 childhood cancer survivors; 169 occurred 5 to 10 years postdiagnosis and 89 > or = 10 years post diagnosis. For the study period as a whole, deaths were attributed to recurrent primary malignancy in 61% of cases, second malignancy in 20%, nonneoplastic treatment complication in 10%, and unintentional injury/suicide in 8%. Late death from recurrent disease decreased significantly for survivors treated in the recent era (P < .0001), while the risk of death from second malignancies increased, although not statistically significantly (P = .10). Projected 15-year survival estimates for all > or = 5-year survivors in both treatment eras was greater than 90%, but differed from expected rates. CONCLUSION: Late mortality from recurrence after treatment for childhood cancer decreases with more effective initial therapy. Prolonged disease-free status is associated with an expected survival that approaches that of the general population for patients treated from 1971 through 1983. The impact of more recent intensified and novel therapies for high-risk patients remains to be determined.

Adolescent↗
PubMed1996

Relationship between cytotoxicity and site-specific DNA recombination after in vitro exposure of leukemia cells to etoposide.

BACKGROUND: Etoposide, an inhibitor of the normal religation activity of the nuclear enzyme topoisomerase II, can induce a secondary acute myeloid leukemia characterized by site-specific DNA rearrangements. The schedule of drug administration appears to be a clinical risk factor for this devastating treatment complication. PURPOSE: We tested the hypothesis that prolonged exposure of leukemia cells in vitro to low concentrations of etoposide, compared with short exposures to high concentrations, could produce equivalent or greater desired cytotoxic effects, with decreased occurrence of undesired site-specific double-stranded DNA recombinational events (i.e., recombinogenesis). METHODS: We used the frequency of V(D)J (variable-diversity-joining) recombinase-mediated deletions of exons 2 and 3 of the hypoxanthine phosphoribosyltransferase (HPRT) gene as a biomarker of etoposide-induced, nonhomologous, site-specific DNA rearrangement. A polymerase chain reaction-based technique was used to measure exon 2 + 3 deletions in human lymphoid leukemia CCRF-CEM cells 6 days after either 4-hour or 24-hour treatment with etoposide at clinically relevant concentrations. Cytotoxic effects of etoposide (determined by the number of viable cells present in the treated compared with the control [i.e., untreated] cells) were measured 6 days after treatment of the cells. The frequency of the exon 2 + 3 deletion following the two treatment-duration conditions was compared by use of the Mantel-Haenszel statistic. All P values resulted from two-sided tests. RESULTS: Cytotoxicity increased with increasing etoposide concentration and exposure duration, as expected. By day 6, the frequency of exon 2 + 3 deletions was significantly higher (global P value = .0003) after the 4-hour treatment than after the 24-hour treatment, regardless of whether the frequency was assessed at etoposide concentrations achieving equivalent (e.g., 95%) cytotoxicity (14.2 x 10(-7) versus 4.1 x 10(-7) or at equivalent etoposide concentrations (e.g., 1 microM) (10.8 x 10(-7) versus 1.3 x 10(-7). Thus, the ratio of desired cytotoxic to undesired recombinogenic effects was higher with the 24-hour schedule. After the treated cells were subcloned at limiting dilutions, the frequency of the exon 2 + 3 deletion increased from 16.3 x 10(-7) to 4.33 x 10(-3), indicating that the recombinational event is not necessarily lethal. CONCLUSION: For all drug concentrations and levels of cytotoxicity studied in CCRF-CEM cells, there was a greater ratio of cytotoxicity to genetic recombination following prolonged exposure to etoposide than following brief exposure. IMPLICATION: These data suggest that recombinogenesis is not inextricably linked to cytotoxicity. If confirmed in the clinical setting, the use of prolonged dosage schedules may provide a means to decrease the risk of etoposide-induced acute myeloid leukemia without compromising treatment efficacy.

Acute Disease↗
PubMed1996

Overt testicular disease at diagnosis is associated with high risk features and a poor prognosis in patients with childhood acute lymphoblastic leukemia.

BACKGROUND: The impact of overt testicular disease on survival was assessed among patients treated at the study institution for childhood acute lymphoblastic leukemia (ALL) over a 15-year period. To the authors' knowledge, the frequency of overt testicular involvement at diagnosis of ALL and its impact on treatment outcome have not been reported previously. METHODS: The medical records of all 651 boys with ALL enrolled on St. Jude Total Therapy Studies X-XIIIA (May 1979 to December 1993) were reviewed to determine the frequency of overt testicular involvement at diagnosis. The log rank test and sequential Cox regression analyses, adjusted for known adverse features, were used to compare event free and overall survival for patients with and without testicular leukemia. A matched-pairs analysis was then conducted for both outcome measures. RESULTS: Thirteen of the 651 male patients (1.9%) presented with overt testicular leukemia. Compared with the other patients, these 13 boys had a significantly higher frequency of infant or adolescent age at diagnosis, hyperleukocytosis, splenomegaly, and mediastinal mass; a poorer 5-year event free survival (38% [95% confidence interval (CI), 15.4-61.4%] vs. 58% [95% CI, 53.6-61.7%], P = 0.06, log rank test); and a significantly poorer 5-year overall survival (37% [95% CI, 14-60.4%] vs. 75% [95% CI, 71.3-78.4%], P = 0.002). The difference in overall, but not event free, survival was supported by sequential Cox regression analyses and by the matched-pairs analysis (P = 0.04). CONCLUSIONS: Overt testicular involvement with leukemia at diagnosis was associated with an adverse survival in boys with ALL. Testicular irradiation may not be necessary in those patients who present with overt testicular involvement. This finding merits prospective evaluation in a larger sample of similarly treated patients.

Adolescent↗