Abstract 2819: Genome-wide CRISPR screen identifies NANP as a radio-sensitizing target of GBM by regulating NF-κB pathway

Glioblastoma multiforme (GBM) are the most malignant primary central nervous system tumors. The standard of care for newly diagnosed GBM patients includes surgery followed by combined radiation therapy (RT) and adjuvant temozolomide (TMZ) therapy. However, one of the therapeutic challenges is the inevitable resistance and recurrence after radiotherapy. Glioblastoma stem cells (GSC) are tumor initiating cells for GBM and plays key roles in radio resistance. Thus, we performed a genome-wide CRISPR screen using a radiation resistant GSC to identify potential RT sensitizing targets. We identified 139 potential RT sensitizing targets with a filter for only those genes associated with a greater than 2-fold reduction in representation with a p<0.05. There were 22 genes with a direct function in key DNA double-strand break repair pathways including 5 genes central to non-homologous end-joining (NHEJ1, XLF, PRKDC, DCLRE1C, XRCC4, LIG4), 6 genes involved in homologous recombination (RAD51D, CYREN, ATM, TONSL, BRCA2, RFWD3), and 7 genes central to initial DNA damage sensing (RNF8, RNF168, TP53BP1, RAD17, FOXM1, RAD9A, RAD1). These results are consistent with the crucial role of DNA repair following radiation exposure and demonstrate the success of the screening. Besides that, one of the top hits is NANP (N-acylneuraminate-9-phosphatase), which is involved in sialic acid synthetic pathway. Knocking down of NANP causes more G2/M arrest followed by apoptosis after radiation. γH2A.X staining and comet assay shows more DNA damage in NANP knock down cells after radiation. Transcriptome analysis reveals NANP inhibition restrain mesenchymal status and NF-κB pathway activation. Furthermore, activation of NF-κB pathway could rescue the RT-induced G2/M arrest of NANP knock down cells. TCGA and CGGA dataset shows NANP is highly expressed in GBM patients and patients with NANP high expression have poorer survival. In conclusion, our study identified NANP as a novel radio-sensitizing target for glioblastoma by regulating NF-κB pathway and mesenchymal status of GSCs.

Citation Format: Yingwen Ding, Ze-Yan Zhang, Ravesanker Ezhilarasan, Aram S. Modrek, Jerome Karp, Erik P. Sulman. Genome-wide CRISPR screen identifies NANP as a radio-sensitizing target of GBM by regulating NF-κB pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2819.

EPCO-19. ADAPTIVE RESPONSES TO GENOME-WIDE DNA DAMAGE RESULT IN TOPOLOGIC GENOME REORGANIZATION IN GLIOBLASTOMA

In glioblastoma, treatment with radiation and chemotherapy leads to DNA-damage and most DNA breaks are faithfully repaired, but the impact on the epigenome is largely unknown. Using newly developed tools to enable these studies, we hypothesize that genome-wide DNA damage leads to local alterations in DNA-methylation, genome organization, and results in persistent gene-expression alterations near sites of repaired damage. We use patient-derived human glioblastoma stem-like cells (GSCs) as a model. DNA breaks are induced using (i) irradiation or (ii) a novel “multi-cut” CRISPR-Cas9 DNA break system followed by multi-omic profiling. With radiation, we find significant and wide-spread alterations in DNA-methylation after treating multiple glioblastoma cultures. However, it is challenging to study local alterations around sites of radiation induced damage because breaks are introduced at different sites in each cell, resulting in stochastic DNA methylation alterations. To circumvent this issue, we developed a multi-cut CRISPR-Cas9 DNA break system that targets 142 or 483 pre-defined loci. Induction of pre-mapped genome-wide cuts reproduces a similar level of toxicity as standard doses of radiation. To assess repair efficiency and confirm induction of breaks, we performed targeted sequencing of the 142 or 483 sites to allow for high coverage sequencing. To understand how DNA damage may lead to regional epigenetic and 3D chromatin organization changes, we performed HiC, Methylation-seq, ChIP-seq of the chromatin organizing factor CTCF and enhancer marker H3K27ac, as well as RNA-seq, before and after cut induction. Our findings show significant mega-base scale alterations in chromatin contacts centered around cut sites, enrichment of DNA methylation alterations at regulatory elements and altered gene-expression. The findings here provide a mechanistic view of the interplay between genome-wide DNA damage, DNA methylation and genome re-organization, and have wide ranging implications for the effect of DNA damage on the epigenome in glioblastoma.

Disparities in the uptake of telemedicine and implications for clinical trial enrollment in breast cancer patients

PURPOSE/OBJECTIVES

Since the COVID-19 pandemic, telemedicine has emerged as an alternative to office visits in routine radiation oncology practice. The purpose of this study was to identify factors associated with patient preference for an initial consult via telemedicine and correlation with clinical trial enrollment.

MATERIALS/METHODS

We evaluated breast cancer patients seen during the open enrollment of a prospective randomized trial from 06/01/2020 to 05/13/2021. Univariate and multivariate logistic regression models were used to identify factors associated with virtual vs in-person initial consultation. All statistical tests were two-sided and the null hypothesis was rejected for p<0.05.

RESULTS

We identified 476 patient consultations with 259 office visits and 217 telemedicine visits. On multivariate analysis, increased age, unemployment, chemotherapy receipt and radiation at our institution were associated with decreased usage of telemedicine for consultation visit. Out of 217 patients who underwent a telemedicine initial consultation, 10% were eligible to enroll on the trial and of those eligible, 76% enrolled. Out of 259 patients who underwent office visit initial consultation, 14% were eligible to enroll on the trial and of those eligible, 53% enrolled. Among eligible patients, there was no statistically significant difference in clinical trial enrollment between telemedicine and office visits.

CONCLUSION

Older patients, unemployed patients, those receiving chemotherapy and those who subsequently received radiation at our institution were less likely to use telemedicine for their initial consult. Despite these disparities in telemedicine usage, there was no difference in clinical trial enrollment. Telemedicine may be an effective platform for clinical trial enrollment though further strategies to improve its access are essential.

Phase I dose escalation trial of sorafenib as a single agent for adults with relapsed and refractory acute leukemias

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Background: Sorafenib is a multikinase inhibitor with activity against B-raf, VEGF, and FLT3. Based on preclinical activity in FLT3 mutant AML, sorafenib was studied in refractory acute leukemia. Methods: The primary objective was to determine the safety and tolerability of sorafenib in refractory acute leukemias. Secondary objectives included pharmacokinetics (PK) and pharmacodynamic (PD) effects of sorafenib on FLT3 phosphorylation. Dose escalation began at 400 mg BIDx14days per month, and proceeded through 600 mg BID x 21 days per month. Plasma concentration of sorafenib and its primary metabolite sorafenib N-oxide were measured by LC/MS//MS method. The plasma inhibitory assay was used to measure target inhibition of phosphorylated FLT3 and phosphorylated Erk. Results: Fifteen patients (13 = AML, 2 = ALL) were enrolled (ages 37–85) and treated on three dosing schedules (400 mg BID x 14 d, 400 mg BID x 21 days, 600 mg BID x 21days) of single agent sorafenib. The maximally tolerated dose was 400 mg BID x 21 days per month. Grade 3 or greater toxicities were experienced in 55% of cycles, most common grade 3 or greater toxicities being fatigue (16%) and hypokalemia (13%). No patients met criteria for complete or partial response, but 11 of 15 (73%) patients experienced stable disease as best response, with 6 showing a reduction in bone marrow blasts after only one cycle, half of who experienced a >50% reduction in bone marrow blasts. Interestingly, 2 pts with FLT3-ITD mutations both showed marrow blast response (1 pt >50%). Sorafenib resulted in sustained complete inhibition of FLT3 and Erk as demonstrated in all patients assessed (n = 11). Importantly, this inhibition was maintained throughout treatment cycle and 3/5 pts had FLT3 inhibitory activity 7 days post their last dose. Correlative studies suggest sorafenib N-oxide is an active metabolite. Conclusions: Sorafenib is a potent inhibitor of FLT3 with favorable PK and PD properties. Clinical activity as a single agent was limited to transient reductions in bone marrow blast counts and dose escalation was limited due to toxicities. Based on PK data in conjunction with standard curves for inhibition of FLT3 by sorafenib in plasma, the minimum FLT3 inhibitory dose of sorafenib is likely less than 400 mg BID.

No significant financial relationships to disclose.

Phase Ib/II pharmacokinetic/pharmacodynamic (PK/PD) study of combination voreloxin and cytarabine in relapsed or refractory AML patients

7005

Background: Voreloxin is a naphthyridine analog that intercalates DNA and inhibits topoisomerase II, inducing apoptosis. Clinical activity is observed in ovarian cancer and AML. Voreloxin combined with cytarabine (Ara-C) show supra-additive activity preclinically. Interim results from a phase Ib/II study in relapsed or refractory AML are reported. Methods: Dose-escalation in relapsed/refractory AML patients (pts) with ≤ 3 prior induction regimens; phase II expansion in first-relapse pts (CR1 ≥ 3 months) at MTD. Voreloxin given d1 and d4, combined with: A) continuous infusion 400 mg/m2/d x 5d Ara-C (CIV), or B) bolus 1 g/m2/d IV x 5d Ara-C. Voreloxin starting dose: A) 10 mg/m2/dose; B) 70 mg/m2/dose. Treatment: induction, reinduction if needed, and up to 2 courses for consolidation. DLT, PK, and PD were assessed in cycle 1. Pts’ PBMC were evaluated for induction of DNA damage response markers. Ex vivo sensitivity of pt BMA to voreloxin and Ara-C were evaluated by CellTiter-Glo proliferation assay. Results: 52 pts treated to date (A: 41 pts, dose-escalation; 5 pts Phase 2; B: 6 pts dose-escalation). A) MTD is 80 mg/m2/dose voreloxin. Infections are the most common G3 or higher toxicity. Voreloxin PK were dose proportional to 50 mg/m2, then plateaued. Evaluation of PBMC pre- and posttreatment suggests modulation of pDNA-PKcs and pChk2 may reflect response. Ex vivo BMA assay results suggest that voreloxin is the primary contributor to the majority of CRs observed. Phase Ib: 9 CRs + CRp were observed in multiply relapsed or 1° refractory pts. B) 70 mg/m2/dose voreloxin, no DLT; too early to evaluate activity. Conclusions: Voreloxin in combination with CIV Ara-C is generally well-tolerated, with CR in relapsed/refractory pts. Enrollment continues: A) phase II; B) phase Ib. Ex vivo activity assay results suggest that voreloxin is the primary contributor to the majority of CR. Induction of pDNA-PKcs and pChk2 in PBMCs from treated pts may reflect response.

[Table: see text]

Poor risk assessment in the elderly receiving cloretazine induction for AML or MDS

18562

Background: Elderly patients (pts) ≥60 years with acute myelogenous leukemia (AML) have lower response rates, and higher morbidity and mortality than younger pts when treated with cytotoxic induction therapy. Common disease-related factors that predict poor response in the elderly are adverse cytogenetics and secondary leukemia (following antecedent hematologic disorder or exposure to chemotherapy). Pt-related factors such as ECOG performance status (PS) and organ dysfunction affect treatment decisions due to poor tolerability and early death. Cloretazine, a novel alkylating agent has significant activity in AML and MDS with a favorable safety profile. A Phase II study of monotherapy induction was conducted in elderly pts with AML or high risk MDS (N = 105, median age 72, range 60–88), with a 31% complete response rate and minimal non-hematologic toxicity. To describe the pts in this study considered “unfit” for 7+3 induction, disease-related and pt-related information was obtained. The Hematopoietic Cell Transplantation Comorbidity Index (Sorrer et al, 2005) (HCT-CI) is a modification of the Charlson Comorbidity Index (Charlson et al.1987), for pts considered for stem cell transplant. Seventeen medical conditions are included with weighted values predicting non-relapse mortality (NRM). Methods: Baseline demographic and pt-related data was obtained from case report forms. In addition to disease-related prognostic indicators, pt-related data was scored by the HCT-CI. Pts were grouped in risk categories for NRM by HCT-CI scores (low = 0, intermediate = 1 or 2; high ≥3). Results: Either or both disease-related poor risk factors were present in 68 pts (65%): 42 pts (40%) had unfavorable cytogenetics and 45 pts (43%) had secondary AML. No pt had favorable cytogenetics. Ninety-four (89%) pts had at least one HCT-CI comorbidity. The most common were cardiac (46%), psychiatric (28%); hepatic (25%) and controlled infection (24%). By HCT-CI, the risk for NRM was low in 10%, intermediate in 32%, and high in 57% of pts. Conclusions: The majority of these elderly pts were poor-risk by disease-related criteria or comorbidities measured by the HCT-CI. This index warrants further testing for determining NRM risk of induction regimens for elderly pts with AML.

[Table: see text]

In vivo imaging of serotonin transporters with [99mTc]TRODAT-1 in nonhuman primates

[99mTc]TRODAT-1 was the first 99mTc-labeled imaging agent to show specific binding to dopamine transporters (DAT) in the striatum (STR) of human brain. Additionally, in vitro binding and autoradiographic experiments demonstrated that this tracer also binds to serotonin transporters (SERT) in the midbrain/hypothalamus (MB) area. In this study, [99mTc]TRODAT-1 was investigated as a potentially useful ligand to image SERT in the MB of living brain. A total of eight single-photon emission tomography (SPET) scans were performed in two baboons (Papio anubis) after intravenous (i.v.) injection of 740 MBq (20 mCi) of [99mTc]TRODAT-1 using a triple-head gamma camera equipped with ultra-high-resolution fan-beam collimators (scan time: 0-210 min). In four blocking studies, baboons were pretreated with (+)McN5652 (1 mg/kg, i.v.) or methylphenidate (1 mg/kg, i.v.) to specifically block SERT or DAT, respectively. After co-registration with magnetic resonance images of the same baboon, a region of interest analysis was performed using predefined templates to calculate specific uptake in the midbrain area and the striatum, with the cerebellum as the background region [(MB-CB)/CB, (STR-CB)/CB]. Additionally, two PET scans of the same baboons were performed after i.v. injections of 74-111 MBq (2-3 mCi) of [11C](+)McN5652 to identify the SERT sites. In [99mTc]TRODAT-1/SPET scans, the SERT sites in the MB region were clearly visualized. Semiquantitative analysis revealed a specific uptake in MB ([MB-CB]/CB) of 0.30+/-0.02, which was decreased to 0. 040+/-0.005 after pretreatment with nonradioactive (+)McN5652, a selective SERT ligand. Pretreatment with methylphenidate reduced the specific binding of [99mTc]TRODAT-1 to DAT sites [(STR-CB)/CB] from 2.45+/-0.13 to 0.32+/-0.04 without any effect on its binding to SERT sites [(MB-CB)/CB], which was confirmed by the co-registration of the [11C](+)McN5652/PET scans. This preliminary study suggests that specific binding of [99mTc]TRODAT-1 to SERT sites can be detected by in vivo SPET imaging despite the low target to background ratio. These findings provide impetus for further development of similar compounds with improved binding affinity and selectivity to SERT sites.

Anxiety sensitivity and self-reported reasons for drug use

Two studies examined the relationships between anxiety sensitivity (AS), drug use, and reasons for drug use. In Study 1, 229 university students (57% F) completed the Anxiety Sensitivity Index (ASI) and a drug use survey, assessing use of a variety of drugs within the last month, and coping reasons for drug use. Consistent with a modified tension-reduction hypothesis, ASI scores were positively correlated with the number of both anxiety- and depression-related reasons for drug use endorsed. In Study 2, 219 university students (74% F) completed the ASI and a drug use survey, assessing use of several drugs (e.g., alcohol, cigarettes, caffeine, and marijuana/hashish) within the last year, and primary reasons (coping, affiliative, or enhancement) for the use of each drug. Marijuana/hashish users reported lower ASI scores than non-users supporting a negative relation between AS and the use of cannabis. ASI scores were positively correlated with the use of alcohol primarily to cope, and negatively correlated with the use of alcohol primarily to affiliate, among both gender groups, and ASI scores were positively correlated with the use of nicotine primarily to cope among the females. Implications of these findings for understanding risk for abuse of stress-response-dampening drugs by high AS individuals are discussed.

Acute leukemia

The acute leukemias continue to present a formidable challenge for which there is not yet a reliably curative 'standard approach' for the majority of adults with this family of diseases. In order to make progress in terms of curing these devastating diseases, we must understand leukemia biology on the clinical, cellular and molecular levels, with exploitation of the leukemia-associated molecular targets in designing strategies aimed at eradicating the leukemic clone. In this review, we will discuss a few key mechanisms of leukemogenesis that represent convergent pathways of malignant transformation and, as such, present pivotal molecular targets for therapy. Specifically, we focus on normal and leukemic hematopoietic cell cycle regulation, issues surrounding DNA damage and repair, programmed cell death (apoptosis) and drug responsiveness, and multidrug resistance as a marker for stem cell involvement and as a novel target for intervention. When functioning normally, such mechanisms determine a cell's ability to respond to DNA damage, traverse the cell cycle and maintain genomic integrity. And in addition to the target cell itself, there are crucial extracellular determinants of hematopoietic cell proliferation and differentiation that modulate net signalling activity and gene expression, cell-cell contact and growth-modulating factors for instance. The molecular dissection of these intersecting pathways, from the extracellular milieu to the genes themselves, in both the normal and transformed states will elucidate the means by which cells escape treatment-induced death. Such understanding should, in turn, lead to the development of targeted therapeutic strategies that exploit differences between normal and malignant cells, overcome the mechanisms by which leukemic cells acquire drug resistance, and enhance the curability of these devastating diseases.

Carcinoma of the lung in HIV-positive patients: findings on chest radiographs and CT scans

OBJECTIVE

Several recent clinical studies have described an association between HIV seropositivity and lung cancer. The purpose of this study was to describe the spectrum of imaging findings in HIV-positive patients who had proved carcinoma of the lung. In particular, we attempted to define the role of CT in diagnosing HIV-associated lung cancer.

MATERIALS AND METHODS

The study population consisted of 23 HIV-positive patients from two institutions who had lung cancer diagnosed between 1989 and 1993. All patients had both chest radiographs and CT scans. The group included 19 men and four women with a mean age of 42 years. The diagnosis of lung cancer was confirmed by bronchoscopy in eight patients, by pleural fluid aspiration or pleural biopsy in seven, by percutaneous needle biopsy of a lung lesion in three, by biopsy of an extrathoracic site in four, and by thoracotomy in one. Two thoracic radiologists retrospectively evaluated the chest radiographs and CT scans to identify parenchymal masses, lymphadenopathy, pleural disease, chest wall or mediastinal invasion, and metastatic lesions.

RESULTS

Fifteen (65%) of the 23 patients had a central or peripheral mass or nodule. Eight (35%) had extensive pleural disease, either as an isolated finding or in combination with other abnormalities. CT scans showed the malignant lesion underlying the extensive pleural disease in all but one case. All patients with extensive pleural disease had adenocarcinoma. No patient in the study was considered a candidate for resection on the basis of clinical and radiologic evaluation.

CONCLUSION

Lung cancer in HIV-positive patients manifested most often on chest radiographs as a central or peripheral mass or nodule. Extensive pleural disease in the absence of an apparent primary lesion was the second most common major manifestation. Lung cancer therefore merits serious consideration in the differential diagnosis of extensive pleural disease in HIV-positive patients. CT was most useful in evaluating malignant lesions associated with extensive pleural disease.

Bone densitometry observations of osteopetrosis in response to bone marrow transplantation

Spinal bone density was measured in eight patients with osteopetrosis to assess the natural history of the disease and to monitor the response to therapy. Quantitative computed tomographic scans of the lumbar vertebra were obtained in seven patients, and dual photon absorptiometric scans were obtained when the technique became available. Six children were afflicted with the infantile malignant recessive condition and two with the less severe dominant condition. In all cases, bone densitometry values ranged from four to five times higher than the mean for normal age and gender-matched controls. In four children with recessive osteopetrosis, quantitative computed tomographic and dual photon absorptiometric scans showed an excellent correlation (R = 0.93) between the methods. Quantitative computed tomographic values ranged from 597 to 730 mg/cm3 (mean = 655 mg/cm3) in children with osteopetrorickets and from 901 to 1000 mg/cm3 (mean = 980 mg/cm3) in the same children when the rickets was cured. In two children treated with bone marrow transplantation, bone densitometry values returned to normal within three years. Bone densitometry provides a safe and noninvasive method for observing the natural history and therapeutic response of the osteopetrotic syndromes.

Lung cancer in patients with immunodeficiency syndrome

We report adenocarcinoma of the lung in seven patients with human immunodeficiency virus (HIV) infection. We compared age, clinical findings and survival data with a sex-matched control group of HIV-negative patients with adenocarcinoma of the lung. Median age of HIV-infected patients with lung cancer was lower than in control patients with lung cancer. The HIV-infected patients had more systemic symptoms and abnormal physical findings than control subjects. Both groups had smoking histories. Laboratory data were similar but control subjects had lower blood oxygen tensions than did HIV patients; HIV patients had more abnormalities on chest roentgenograms and computed tomography scans than did control subjects. All HIV-infected patients were stage IV. Median survival was 4 weeks. For control patients, 50 percent had stage IV disease; median survival was 25.5 weeks. Thus, patients with HIV infection develop lung cancer at a younger age than sex-matched control subjects and undergo a more fulminant course with shortened survivals.

Occlusion of the melatonin-free interval blocks the short day gonadal response of the male Syrian hamster to programmed melatonin infusions of necessary duration and amplitude

Abstract Photoperiodic control of the neuroendocrine axis is mediated by changes in the duration of the nocturnal melatonin signal. This study tested the hypothesis that reading of the signal depends upon the presence of a period free of melatonin between successive signals. Adult male Syrian hamsters were pinealectomized and received chronic subcutaneous infusions of melatonin or saline for 6 weeks. Animals which received saline had large testes. Those which received a single daily infusion which lasted for 10 h (50 ng/h) followed by 14 h without infusion underwent gonadal atrophy. Other animals received a compound melatonin signal in which the melatonin-free interval was occluded by a continuous infusion (25 ng/h). Superimposed upon this was a 10 h phasic increase in infusion rate such that the maximum rate of infusion was equivalent to that observed in controls (25 ng/h increase, 50 ng/h peak rate), or the increase in rate over the baseline was the same as in controls (50 ng/h increase, 75 ng/h peak rate). In neither group did the animals undergo gonadal regression. Analysis of iodomelatonin binding sites by in vitro autoradiography failed to reveal any systematic difference between animals which did and did not respond to melatonin and so the absence of a response could not be attributed to loss of receptors. These data demonstrate that the photoperiodic system cannot identify the melatonin signal solely upon the features of nocturnal peak height or amplitude of the peak over baseline. They are consistent with the hypothesis that the melatonin-free interval plays a significant role in photoperiodic time measurement.

Magnetic resonance imaging of experimental demyelinating lesions

An animal model of central nervous system demyelination was created by injecting rat internal capsules with lysophosphatidylcholine (LPC). The resulting chemically induced demyelinating lesions were readily visible in T1-weighted spin-echo, T2 weighted spin-echo, and inversion-recovery magnetic resonance imaging (MRI) sequences. Changes in lesions were followed over 8 weeks and correlated with histopathology. Histologically, lesions were characterized initially by an acute, inflammatory phase with edema and blood-brain barrier breakdown, followed by macrophage-mediated removal of myelin debris and finally by remyelination after 3 to 4 weeks. MRI can differentiate lesion stages in the LPC model and may be useful in investigating mechanistic aspects of the demyelinating process. In addition the well-localized lesions may be amenable to study by techniques of volume-localized NMR spectroscopy.

Blood lead, calcium status, and behavior in preschool children

To determine if calcium status is associated with blood lead levels and behavior, 64 black urban children aged 18 to 47 months were studied. Twenty-seven controls (blood lead levels, less than 1.45 mumol/L) were compared with 37 cases (blood lead levels, greater than or equal to 1.45 mumol/L) with respect to four calcium measures (calcium intake, serum calcium level, 1,25-dihydroxyvitamin D level, and bone densitometric findings) and three behavioral scores. Levels of 25-hydroxyvitamin D provided a measure of vitamin D sufficiency. As expected, blood lead level was associated with pica scores. However, none of the calcium measures differed between cases and controls. Controlling for four confounders (season, pica score, maternal education, and sex), yielded no significant differences between the two groups in the mean values of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D level. There was no interaction between blood lead level and the four covariates. No relationship could be demonstrated between calcium status and the pica scores.

Bone mineral content in black pre-schoolers: normative data using single photon absorptiometry

Fifty-nine children aged 18 to 47 months with normal and elevated blood lead levels had bone mineral density (BMD in gm/cm2) and bone mineral content (BMC in gm/cm) measured using the technique of single photon absorptiometry of the radius shaft. No normative data are available for black children of this age group. Moderate elevations of blood lead were not found to influence bone mineralization. The BMC of the study children was significantly higher than the published values for white children of the same age. We found no statistical difference between the bone mineral density of males and females in this age group.

Single photon absorptiometry imaging as a screening method for diminished dual photon density measures

Scanning of the new 5-mm distal-radius site and the mid-radius (33% site) was performed using single photon absorptiometry (SPA) and of the L2-L4 region of the spine using dual photon absorptiometry (DPA) in a group of healthy women (age range 36-66 yr) in order to develop parameters to enable SPA to be used to screen for low DPA measures. The study data were analyzed as follows: 1. Women were classified as either 'intact' or 'post pelvic surgery' and the data for the two groups were separated. 2. Each SPA measurement was scrutinized and the one which produced the lowest score (% young normal [YN]) was entered for data analysis and graphing. The application of these two analytical discriminators represents a new approach in the biomedical literature. The findings were as follows: 1. When women were separated according to whether they were intact or had undergone pelvic surgery, the threshold value for screening using radius measures among intact women was set at 80% YN. 2. The necessary threshold value for the pelvic-surgery group needed to be set higher, at 93% YN. 3. If either the distal density or the mid-shaft density was below its threshold level, DPA was indicated. 4. At these threshold levels, no women with diminished spinal density (less than 83% YN) were omitted from screening procedure. We conclude that by refining our evaluation of each healthy woman according to her pelvic physiology status (intact or post-surgery) and considering whether either of the two SPA measures is below the threshold value, we will be able to screen for diminished DPA density and thereby eliminate a significant number of expensive but uninformative DPA readings.

Norfloxacin for prevention of bacterial infections in granulocytopenic patients

The efficacy and safety of norfloxacin were compared with those of placebo, vancomycin-polymyxin, and trimethoprim-sulfamethoxazole (TMP/SMX) for prophylaxis of bacterial infections in granulocytopenic patients. The study results showed that norfloxacin treatment, which was well tolerated and not associated with any serious systemic adverse effects, prevented acquisition of gram-negative bacillary organisms. Fewer norfloxacin-treated patients (38 of 108 patients, or 35 percent) experienced microbiologically documented infections compared with patients receiving placebo (27 of 40 patients, or 68 percent), vancomycin-polymyxin (16 of 30 patients, or 53 percent), or TMP/SMX (14 of 28 patients, or 50 percent). Gram-negative bacteremia developed in five of 108 norfloxacin-treated patients (5 percent), compared with 17 of 40 placebo-treated patients (43 percent), five of 30 treated with vancomycin-polymyxin (17 percent), and one of 28 patients treated with TMP/SMX (4 percent). The incidence of gram-positive bacteremia was similar in all study groups and was not affected by norfloxacin or any other oral prophylactic antibiotics. These results suggest that norfloxacin is both safe and effective for the prevention of serious gram-negative bacillary infections in granulocytopenic patients. More effective prophylaxis of gram-positive bacterial infections, however, is needed.