Structure of an RNA G-quadruplex from the West Nile virus genome.

Potential G-quadruplex sites have been identified in the genomes of DNA and RNA viruses and proposed as regulatory elements. The genus Orthoflavivirus contains arthropod-transmitted, positive-sense, single-stranded RNA viruses that cause significant human disease globally. Computational studies have identified multiple potential G-quadruplex sites that are conserved across members of this genus. Subsequent biophysical studies established that some G-quadruplexes predicted in Zika and tickborne encephalitis virus genomes can form and known quadruplex binders reduced viral yields from cells infected with these viruses. The susceptibility of RNA to degradation and the variability of loop regions have made structure determination challenging. Despite these difficulties, we report a high-resolution structure of the NS5-B quadruplex from the West Nile virus genome. Analysis reveals two stacked tetrads that are further stabilized by a stacked triad and transient noncanonical base pairing. This structure expands the landscape of solved RNA quadruplex structures and demonstrates the diversity and complexity of biological quadruplexes. We anticipate that the availability of this structure will assist in solving further viral RNA quadruplexes and provides a model for a conserved antiviral target in Orthoflavivirus genomes.

Dissection of integrated readout reveals the structural thermodynamics of DNA selection by transcription factors.

Nucleobases such as inosine have been extensively utilized to map direct contacts by proteins in the DNA groove. Their deployment as targeted probes of dynamics and hydration, which are dominant thermodynamic drivers of affinity and specificity, has been limited by a paucity of suitable experimental models. We report a joint crystallographic, thermodynamic, and computational study of the bidentate complex of the arginine side chain with a Watson-Crick guanine (Arg×GC), a highly specific configuration adopted by major transcription factors throughout the eukaryotic branches in the Tree of Life. Using the ETS-family factor PU.1 as a high-resolution structural framework, inosine substitution for guanine resulted in a sharp dissection of conformational dynamics and hydration and elucidated their role in the DNA specificity of PU.1. Our work suggests an under-exploited utility of modified nucleobases in untangling the structural thermodynamics of interactions, such as the Arg×GC motif, where direct and indirect readout are tightly integrated.

X-ray Structure Characterization of the Selective Recognition of AT Base Pair Sequences.

The rational design of small molecules that target specific DNA sequences is a promising strategy to modulate gene expression. This report focuses on a diamidinobenzimidazole compound, whose selective binding to the minor groove of AT DNA sequences holds broad significance in the molecular recognition of AT-rich human promoter sequences. The objective of this study is to provide a more detailed and systematized understanding, at an atomic level, of the molecular recognition mechanism of different AT-specific sequences by a rationally designed minor groove binder. The specialized method of X-ray crystallography was utilized to investigate how the sequence-dependent recognition properties in general, A-tract, and alternating AT sequences affect the binding of diamidinobenzimidazole in the DNA minor groove. While general and A-tract AT sequences give a narrower minor groove, the alternating AT sequences intrinsically have a wider minor groove which typically constricts upon binding. A strong and direct hydrogen bond between the N-H of the benzimidazole and an H-bond acceptor atom in the minor groove is essential for DNA recognition in all sequences described. In addition, the diamidine compound specifically utilizes an interfacial water molecule for its DNA binding. DNA complexes of AATT and AAAAAA recognition sites show that the diamidine compound can bind in two possible orientations with a preference for water-assisted hydrogen bonding at either cationic end. The complex structures of AAATTT, ATAT, ATATAT, and AAAA are bound in a singular orientation. Analysis of the helical parameters shows a minor groove expansion of about 1 Å across all the nonalternating DNA complexes. The results from this systematic approach will convey a greater understanding of the specific recognition of a diverse array of AT-rich sequences by small molecules and more insight into the design of small molecules with enhanced specificity to AT and mixed DNA sequences.

DNA selection by the master transcription factor PU.1.

The master transcriptional regulator PU.1/Spi-1 engages DNA sites with affinities spanning multiple orders of magnitude. To elucidate this remarkable plasticity, we have characterized 22 high-resolution co-crystallographic PU.1/DNA complexes across the addressable affinity range in myeloid gene transactivation. Over a purine-rich core (such as 5'-GGAA-3') flanked by variable sequences, affinity is negotiated by direct readout on the 5' flank via a critical glutamine (Q226) sidechain and by indirect readout on the 3' flank by sequence-dependent helical flexibility. Direct readout by Q226 dynamically specifies PU.1's characteristic preference for purines and explains the pathogenic mutation Q226E in Waldenström macroglobulinemia. The structures also reveal how disruption of Q226 mediates strand-specific inhibition by DNA methylation and the recognition of non-canonical sites, including the authentic binding sequence at the CD11b promoter. A re-synthesis of phylogenetic and structural data on the ETS family, considering the centrality of Q226 in PU.1, unifies the model of DNA selection by ETS proteins.

Evaluation of plasma nucleosome concentrations in dogs with a variety of common cancers and in healthy dogs.

BACKGROUND: Cell free DNA, in the form of nucleosomes, is released into circulation during apoptosis and necrosis in a variety of diseases. They are small fragments of chromosomes that are composed of DNA wrapped around a histone core made of four duplicate histone proteins forming an octamer. The nucleosome compartment is a relatively uninvestigated area of circulating tumor biomarkers in dogs. The objectives of this study were to quantify and better characterize nucleosome concentrations in 528 dogs with various common malignancies and compare them to 134 healthy dogs. RESULTS: The sensitivity of increased circulating nucleosome concentrations for the detection of cancer in all dogs was 49.8% with a specificity of 97% with an area under the curve of 68.74%. The top 4 malignancies detected by the test included lymphoma, hemangiosarcoma, histiocytic sarcoma and malignant melanoma. The malignancies least likely to be detected were soft tissue sarcomas, osteosarcoma and mast cell tumors. CONCLUSIONS: A variety of tumor types may cause increased nucleosome concentrations in dogs. Tumors of hematopoietic origin are most likely to cause elevations and local tumors such as soft tissue sarcomas are least likely to cause elevations in plasma nucleosome concentrations.

Melanoma in women of childbearing age and in pregnancy in California, 1994-2015: a population-based cohort study.

BACKGROUND: Melanoma is one of the most common malignancies during pregnancy. There is debate regarding the impact of pregnancy on the prognosis of melanoma. Recent large population-based studies from the United States are lacking. OBJECTIVES: To determine the characteristics and survival of women with pregnancy-associated melanoma. METHODS: This population-based, retrospective cohort study used California Cancer Registry data linked with state-wide hospitalization and ambulatory surgery data to identify 15-44-year-old female patients diagnosed with melanoma in 1994-2015, including pregnant patients. Multivariable logistic regression compared demographic and clinical characteristics between pregnant and non-pregnant women with melanoma. Multivariable cox proportional hazards regression models assessed melanoma-specific and overall survival. RESULTS: We identified 13 108 patients, of which 1406 were pregnant. Pregnancy-associated melanoma was more frequent in Hispanic compared to non-Hispanic White women. Melanoma occurring post-partum was associated with greater tumour thickness (2.01-4.00 vs. 0.01-1.00 mm, odds ratio 1.75, 95% confidence interval: 1.03-2.98). There were otherwise no significant differences between pregnant and non-pregnant women. Worse survival was associated with Asian, Black and Native American race/ethnicity (vs. non-Hispanic White), lower neighbourhood socio-economic status, public insurance, tumour site, greater tumour thickness and lymph node involvement, but not pregnancy. CONCLUSIONS: Melanoma occurring post-partum was associated with greater tumour thickness, but pregnancy status did not affect survival after melanoma. Race/ethnicity, socio-economic status and health insurance impacted survival, emphasizing the importance of reducing health disparities.

Drug design and DNA structural research inspired by the Neidle laboratory: DNA minor groove binding and transcription factor inhibition by thiophene diamidines.

The understanding of sequence-specific DNA minor groove interactions has recently made major steps forward and as a result, the goal of development of compounds that target the minor groove is an active research area. In an effort to develop biologically active minor groove agents, we are preparing and exploring the DNA interactions of diverse diamidine derivatives with a 5'-GAATTC-3' binding site using a powerful array of methods including, biosensor-SPR methods, and X-ray crystallography. The benzimidazole-thiophene module provides an excellent minor groove recognition component. A central thiophene in a benzimidazole-thiophene-phenyl aromatic system provides essentially optimum curvature for matching the shape of the minor groove. Comparison of that structure to one with the benzimidazole replaced with an indole shows that the two structures are very similar, but have some interesting and important differences in electrostatic potential maps, the DNA minor groove binding structure based on x-ray crystallographic analysis, and inhibition of the major groove binding PU.1 transcription factor complex. The binding KD for both compounds is under 10 nM and both form amidine H-bonds to DNA bases. They both have bifurcated H-bonds from the benzimidazole or indole groups to bases at the center of the -AATT- binding site. Analysis of the comparative results provides an excellent understanding of how thiophene compounds recognize the minor groove and can act as transcription factor inhibitors.

Nursing and Health Care Preferences Among Opioid and Stimulant Using Black Sexual Minority Men: An Exploratory Study.

ABSTRACT: Black sexual minority men (BSMM) experience the worst HIV treatment outcomes in the United States. Drug use increases HIV transmission risks and reduces health care engagement. Perceived health care provider stigma and medical mistrust minimizes treatment efforts. This study identified nursing and health care preferences among drug-using BSMM. In-depth qualitative interviews were conducted among 30 BSMM who reported drug use in Baltimore City, MD, from December 2018 to March 2019. Analysis identified themes as client preferences for nursing practices and gaps in clinical services. Participants' ages ranged from 23 to 63 years (M = 41.1). Most (91%) reported living with HIV. The following themes were identified as nursing and health care preferences: (a) being genuine, (b) knowing drug treatment and social services, (c) understanding drug use effects, (d) providing mental health services, and (e) clarifying treatment recommendations. Nurses and health care facilities can improve cultural competency for drug-using BSMM. Future research should identify the impact of these preferences on HIV care outcomes among BSMM.

"Blocking" and "Filtering": a Commentary on Mobile Technology, Racism, and the Sexual Networks of Young Black MSM (YBMSM).

While research investigates the role and influence of geo-social networking (GSN) applications on HIV, less is known about the impact of GSN functions on disease transmission. In our formative research on young Black men who have sex with men's (YBMSM) technology use patterns and preferences for a smartphone-based HIV prevention intervention, we found that study participants used GSN "block" and "filter" functions as protective mechanisms against racism and racial sexual discrimination. Yet, we suggest that these functions may unintentionally create restrictive sexual networks that likely increase their risk for disease transmission. As such, we contend that attention to the unintended effects of these protective mechanisms against racism on GSN applications is fundamentally a public health issue that requires more research and explicit intervention. Ultimately, we use this work to hypothesize the role of blocking and filtering as a strategy to avoid racism on GSN applications that may partly explain HIV disparities among YBMSM.

Getting PrEPared for HIV Prevention Navigation: Young Black Gay Men Talk About HIV Prevention in the Biomedical Era.

Biomedical HIV prevention strategies, such as pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP), represent new opportunities to reduce critically high HIV infection rates among young black men who have sex with men (YBMSM). We report results of 24 dyadic qualitative interviews (N=48), conducted in Los Angeles, CA, exploring how YBMSM and their friends view PrEP and PEP. Interviews were analyzed using a grounded theory approach. Participants had widely divergent levels of knowledge about these prevention methods. Misconceptions and mistrust regarding PrEP were common, and concerns were expressed about PrEP-related stigma and the potential for gossip among peers who might assume a person on PrEP was HIV-positive. Yet participants also framed PrEP and PEP as valuable new options within an expanded "tool kit" of HIV prevention strategies that created possibilities for preventing new HIV infections, dating men with a different HIV status, and decreased anxiety about exposure to HIV. We organized themes around four main areas: (1) information and misinformation about biomedical HIV prevention; (2) expectations about PrEP, sexual behavior, and stigma; (3) gossip, disclosure, and "spreading the word" about PrEP and PEP; and (4) the roles of PrEP and PEP in an expanded HIV prevention tool kit. The findings suggest a need for guidance in navigating the increasingly complex array of HIV-prevention options available to YBMSM. Such "prevention navigation" could counter misconceptions and address barriers, such as stigma and mistrust, while helping YBMSM make informed selections from among expanded HIV prevention options.

SU-E-J-62: Comparison of Brainlab ExacTrac, AlignRT, and CBCT Positional Accuracy for SRS Set-Up on a TrueBeam STx.

PURPOSE: To compare the ability of Brainlab ExacTrac (Brainlab AG, Feldkirchen, Germany) x-ray (XRAY), Brainlab infrared array (IR), cone beam CT (CBCT), and AlignRT (VisionRT Ltd., London, UK) to accurately measure patient displacement during stereotactic radiosurgery (SRS) on a Varian TrueBeam STx (Varian Inc, Palo Alto, CA). METHODS AND MATERIALS: A CT scan was obtained for a custom skull phantom placed in a Brainlab frameless SRS immobilization system with the Brainlab CT localizer box attached. A generic plan was created in Brainlab iPlan and sent to Brainlab ExacTrac, to AlignRT, and to the TrueBeam. The skull phantom was set-up on the TrueBeam and positioned to isocenter using XRAY. Next, CBCT and IR were acquired and evaluated to determine baseline positions for these methods. A new AlignRT reference surface was acquired as baseline. The phantom was then displaced 2 mm in the vertical, lateral, and longitudinal dimensions using the TrueBeam couch (the couch tolerance is 0.1 mm in each dimension). New XRAY, IR, CBCT, and AlignRT data was acquired in this position. RESULTS: Initially, all methods found that the phantom was positioned with < 0.3 mm accuracy. After the shiftes, XRAY suggested shifts were 2.0, 2,1, 1.8 mm in the vertical, longitudinal, and lateral dimensions, respectively. The IR shifts were 1.7, 2.6, 2.1 mm. The CBCT shifts were 1.8, 1.8, 2.1 mm. The AlignRT shifts were 2.2, 1.6, 1.4 mm. CONCLUSION: The internal XRAY and CBCT methods produced slightly better agreement with the table shifts. The external IR and AlignRT methods were less accurate, but still gave agreement of <= 0.6 mm. Note, the AlignRT cameras did not produce a clean surface off of the phantom. Improved accuracy is expected from a skin surface. This is preliminary work, more extensive study is needed to evaluate these methods.

SU-E-T-144: Daily and Monthly Quality Assurance with TomoDose.

PURPOSE: Examine the use of TomoDose for Tomotherapy quality assurance. METHODS: Baseline TomoDose profiles are acquired annually in accordance with TG-148. During monthly quality assurance, TomoDose is irradiated with a static beam and referenced to baseline. Differences between superimposed profiles are evaluated monthly. TomoDose is further utilized in verifying transverse laser alignment. The TomoDose is aligned to virtual isocenter lasers and statically irradiated with a 40cm × 5.02cm treatment beam. Next, the TomoDose's internal diodes are imaged using the MVCT. Transverse laser, imaging beam, and treatment beam field center are verified to less than 1mm coincidence difference. For daily TomoDose irradiation the couch is set to a fixed height and irradiated. The dose to the central axis and dose rate is recorded. To check energy, the measurement is repeated with an aluminum block placed centrally on the TomoDose. The output reading relative to the dose rate is compared to the baseline determined at the time of monthly verification. A ratio of the output and energy readings serves as a daily energy constancy check. RESULTS: Over 28 months, for nominal field sizes of 1.05, 2.50, and 5.02cm, TomoDose measured an average field size of 1.10, 2.51, and 5.02cm with maximum deviations of 0.09, 0.09, and 0.10cm, respectively. For transverse laser alignment, TomoDose software calculates beam center location. We have found the alignment to be sensitive to sub-millimeter changes. Our nominal daily energy ratio is 0.689. We have observed a decline from an estimated 0.693 to 0.680 with target wear, providing a good indicator of degradation. CONCLUSIONS: TomoDose serves as a reliable constancy device with added benefits of verifying transverse laser alignment and predicting target health. I own common stock in Accuray (Tomotherapy).

SU-E-T-304: Evaluation of Mammosite Multi-Lumen Rotation and Its Dosimetric Consequences.

PURPOSE: To evaluate the dosimetric impact of MammoSite Multi-Lumen (MSML) rotation in phantom and patient studies. METHODS AND MATERIALS: A MSML phantom with an asymmetric dose distribution was created. Target volume coverage and dose at a fixed point 1 cm from the MSML were evaluated as functions of rotation about three orthogonal axes (where the origin was set at the center of the MSML and axis one ran along the central catheter). Additionally, for three MSML patients that were set-up by aligning the stem of the MSML to skin marks, CT scans were acquired before each fraction. Rotation about three axes and maximum point dose to skin and chestwall were evaluated. RESULTS: In phantom, 10° rotations about the central, second, and third axes give average absolute point dose changes with respect to the maximum dose of 1.9%, 3.7%, and 4.2%, respectively; and changes in PTV coverage of 0.9%, 1.0%., and 0.8%, respectively. For patients 1-3 the average absolute rotation about the central axis was 13.60, 9.50, and 7.20, respectively; axis two was 7.00, 3.20, and 11.40, respectively; axis three was 2.90, 2.90, and 3.80, respectively. For cases 1-3 the average absolute change per fraction in maximum point dose to the skin was 0.29 Gy, 0.14 Gy, and 0.39 Gy, respectively; to the chestwall was 0.17 Gy, 0.20 Gy, and 0.21 Gy, respectively. CONCLUSION: Phantom studies showed change in point dose and PTV coverage for a 10° rotation about the central catheter yields < 2% variance. Patient data indicates skin mark alignment is capable of positioning the MSML with 10° accuracy about the central axis. Thus, central axis rotation can be adequately accounted for by skin mark alignment. However, review of the patient data shows that rotations about the other axes are equally important and should be considered and managed.

SU-E-T-641: Flattening Filter Free Dynamic Conformal Arcs for Lung Radiotherapy.

PURPOSE: To investigate the use of dynamic conformal arcs (DCA) with the flattening filter free (FFF) beams for lung stereotactic body radiotherapy (SBRT) on the TrueBeam STx (Varian, Inc., Palo Alto, CA). METHODS: Eight SBRT patients receiving 10-18 Gy per fraction were planned in Eclipse 10 (Varian Medical Systems, Palo Alto, CA) for the TrueBeam STx using DCA's with 6 MV FFF beams. The isocenter was placed such that the point fell near midline on each patient allowing full arc rotation without patient collision.Several planning methods were employed depending on the location of the tumor. For peripheral tumors a single arc was used. For peripheral tumors with chestwall interference, additional oblique fields were used to help pull dose off of the chestwall. For tumors located in the central region or close to the spine, multiple DCA's were used. One standard open DCA was used to deliver the majority of the dose, then one or two additional DCA's with organs blocked automatically using the'Fit and Shield' feature of Eclipse were used to help shape the dose. The arcs were then weighted to create the desired dose distribution. RESULTS: Beam on times for the 8 patients averaged 2.00 minutes with a minimum time of 1.22 minutes and a maximum time of 3.3 minutes total. With multiple arcs or additional static fields, treatment time is lengthened by the time it takes to mode up between arcs (∼1 minute) and/or move between fields. The PTV coverage of the 100% isodose line was >= 95% in all cases. The conformality index ranged 1.12 - 4.5, with an average of 2.5. CONCLUSIONS: FFF DCA is a fast, efficient way to plan and delivery SBRT treatments. The short treatment times directly lead to reduced patient motion and discomfort, which may yield improved targeting and outcomes.

The functions of key residues in the inhibitor, substrate and cofactor sites of human 3beta-hydroxysteroid dehydrogenase type 1 are validated by mutagenesis.

In postmenopausal women, human 3beta-hydroxysteroid dehydrogenase type 1 (3beta-HSD1) is a critical enzyme in the conversion of DHEA to estradiol in breast tumors, while 3beta-HSD2 participates in the production of cortisol and aldosterone in the human adrenal gland. The goals of this project are to determine if Arg195 in 3beta-HSD1 vs. Pro195 in 3beta-HSD2 in the substrate/inhibitor binding site is a critical structural difference responsible for the higher affinity of 3beta-HSD1 for inhibitor and substrate steroids compared to 3beta-HSD2 and whether Asp61, Glu192 and Thr8 are fingerprint residues for cofactor and substrate binding using site-directed mutagenesis. The R195P-1 mutant of 3beta-HSD1 and the P195R-2 mutant of 3beta-HSD2 have been created, expressed, purified and characterized kinetically. Dixon analyses of the inhibition of the R195P-1 mutant, P195R-2 mutant, wild-type 3beta-HSD1 and wild-type 3beta-HSD2 by trilostane has produced kinetic profiles that show inhibition of 3beta-HSD1 by trilostane (K(i)=0.10microM, competitive) with a 16-fold lower K(i) and different mode than measured for 3beta-HSD2 (K(i)=1.60microM, noncompetitive). The R195P-1 mutation shifts the high-affinity, competitive inhibition profile of 3beta-HSD1 to a low-affinity (trilostane K(i)=2.56microM), noncompetitive inhibition profile similar to that of 3beta-HSD2 containing Pro195. The P195R-2 mutation shifts the low-affinity, noncompetitive inhibition profile of 3beta-HSD2 to a high-affinity (trilostane K(i)=0.19microM), competitive inhibition profile similar to that of 3beta-HSD1 containing Arg195. Michaelis-Menten kinetics for DHEA, 16beta-hydroxy-DHEA and 16alpha-hydroxy-DHEA substrate utilization by the R195P-1 and P195R-2 enzymes provide further validation for higher affinity binding due to Arg195 in 3beta-HSD1. Comparisons of the Michaelis-Menten values of cofactor and substrate for the targeted mutants of 3beta-HSD1 (D61N, D61V, E192A, T8A) clarify the functions of these residues as well.

Structure/function of the inhibition of human 3beta-hydroxysteroid dehydrogenase type 1 and type 2 by trilostane.

The human type 1 (placenta, breast tumors) and type 2 (gonads, adrenals) isoforms of 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD) are key enzymes in biosynthesis of all active steroid hormones. Human 3beta-HSD1 is a critical enzyme in the conversion of DHEA to estradiol in breast tumors and may be a major target enzyme for the treatment of breast cancer. 3beta-HSD2 participates in the production of cortisol and aldosterone in the human adrenal gland. The goals of this project are to evaluate the role of the 2alpha-cyano group on trilostane (2alpha-cyano-4alpha,5alpha-epoxy-17beta-ol-androstane-3-one) and determine which amino acids may be critical for 3beta-HSD1 specificity. Trilostane without the 2alpha-cyano group, 4alpha,5alpha-epoxy-testosterone, was synthesized. Using our structural model of 3beta-HSD1, trilostane or 4alpha,5alpha-epoxy-testosterone was docked in the active site using Autodock 3.0, and the potentially critical residues (Met187 and Ser124) were identified. The M187T and S124T mutants of 3beta-HSD1 were created, expressed and purified. Dixon analyses of the inhibition of wild-type 3beta-HSD1, 3beta-HSD2, M187T and S124T by trilostane and 4alpha,5alpha-epoxy-testosterone suggest that the 2alpha-cyano group of trilostane is anchored by Ser124 in both isoenzymes. Kinetic analyses of cofactor and substrate utilization as well as the inhibition kinetics of M187T and the wild-type enzymes suggest that the 16-fold higher-affinity inhibition of 3beta-HSD1 by trilostane may be related to the presence of Met187 in 3beta-HSD1 and Thr187 in 3beta-HSD2. This structure/function information may lead to the production of more highly specific inhibitors of 3beta-HSD1 to block the hormone-dependent growth of breast tumors.

Eight Americas: investigating mortality disparities across races, counties, and race-counties in the United States.

BACKGROUND: The gap between the highest and lowest life expectancies for race-county combinations in the United States is over 35 y. We divided the race-county combinations of the US population into eight distinct groups, referred to as the "eight Americas," to explore the causes of the disparities that can inform specific public health intervention policies and programs. METHODS AND FINDINGS: The eight Americas were defined based on race, location of the county of residence, population density, race-specific county-level per capita income, and cumulative homicide rate. Data sources for population and mortality figures were the Bureau of the Census and the National Center for Health Statistics. We estimated life expectancy, the risk of mortality from specific diseases, health insurance, and health-care utilization for the eight Americas. The life expectancy gap between the 3.4 million high-risk urban black males and the 5.6 million Asian females was 20.7 y in 2001. Within the sexes, the life expectancy gap between the best-off and the worst-off groups was 15.4 y for males (Asians versus high-risk urban blacks) and 12.8 y for females (Asians versus low-income southern rural blacks). Mortality disparities among the eight Americas were largest for young (15-44 y) and middle-aged (45-59 y) adults, especially for men. The disparities were caused primarily by a number of chronic diseases and injuries with well-established risk factors. Between 1982 and 2001, the ordering of life expectancy among the eight Americas and the absolute difference between the advantaged and disadvantaged groups remained largely unchanged. Self-reported health plan coverage was lowest for western Native Americans and low-income southern rural blacks. Crude self-reported health-care utilization, however, was slightly higher for the more disadvantaged populations. CONCLUSIONS: Disparities in mortality across the eight Americas, each consisting of millions or tens of millions of Americans, are enormous by all international standards. The observed disparities in life expectancy cannot be explained by race, income, or basic health-care access and utilization alone. Because policies aimed at reducing fundamental socioeconomic inequalities are currently practically absent in the US, health disparities will have to be at least partly addressed through public health strategies that reduce risk factors for chronic diseases and injuries.

Sentinel node localization in oral cavity and oropharynx squamous cell cancer.

OBJECTIVE: To evaluate the feasibility and predictive ability of the sentinel node localization technique for patients with squamous cell carcinoma of the oral cavity or oropharynx and clinically negative necks. DESIGN: Prospective, efficacy study comparing the histopathologic status of the sentinel node with that of the remaining neck dissection specimen. SETTING: Tertiary referral center. PATIENTS: Patients with T1 or T2 disease and clinically negative necks were eligible for the study. Nine previously untreated patients with oral cavity or oropharyngeal squamous cell carcinoma were enrolled in the study. INTERVENTIONS: Unfiltered technetium Tc 99m sulfur colloid injections of the primary tumor and lymphoscintigraphy were performed on the day before surgery. Intraoperatively, the sentinel node(s) was localized with a gamma probe and removed after tumor resection and before neck dissection. MAIN OUTCOME MEASURES: The primary outcome was the negative predictive value of the histopathologic status of the sentinel node for predicting cervical metastases. RESULTS: Sentinel nodes were identified in 9 previously untreated patients. In 5 patients, there were no positive nodes. In 4 patients, the sentinel nodes were the only histopathologically positive nodes. In previously untreated patients, the sentinel node technique had a negative predictive value of 100% for cervical metastasis. CONCLUSIONS: Our preliminary investigation shows that sentinel node localization is technically feasible in head and neck surgery and is predictive of cervical metastasis. The sentinel node technique has the potential to decrease the number of neck dissections performed in clinically negative necks, thus reducing the associated morbidity for patients in this group.

Xerostomia and its predictors following parotid-sparing irradiation of head-and-neck cancer.

PURPOSE: To assess long-term xerostomia in patients receiving parotid-sparing radiation therapy (RT) for head-and-neck cancer, and to find the patient and therapy-related factors that affect its severity. PATIENTS AND METHODS: From March 1994 through January 2000, 84 patients received comprehensive bilateral neck RT using conformal and multisegmental intensity-modulated RT (IMRT) aiming to spare the major salivary glands. Before RT and periodically through 2 years after the completion of RT, salivary flow rates from each of the major salivary glands were selectively measured. At the same time intervals, each patient completed an 8-item self-reported xerostomia-specific questionnaire (XQ). To gain a relative measure of the effect of RT on the minor salivary glands, whose output could not be measured, the surfaces of the oral cavity (extending to include the surface of the base of tongue) were outlined in the planning CT scans. The mean doses to the new organ ("oral cavity") were recorded. Forty-eight patients receiving unilateral neck RT were similarly studied and served as a benchmark for comparison. Factors predicting the XQ scores were analyzed using a random-effects model. RESULTS: The XQ was found to be reliable and valid in measuring patient-reported xerostomia. The spared salivary glands which had received moderate doses in the bilateral RT group recovered to their baseline salivary flow rates during the second year after RT, and the spared glands in the unilateral RT group, which had received very low doses, demonstrated increased salivary production beyond their pre-RT levels. The increase in the salivary flow rates during the second year after RT paralleled an improvement in xerostomia in both patient groups. The improvement in xerostomia was faster in the unilateral compared with the bilateral RT group, but the difference narrowed at 2 years. The major salivary gland flow rates had only a weak correlation with the xerostomia scores. Factors found to be independently associated with the xerostomia scores were the pre-RT baseline scores, the time since RT, and the mean doses to the major salivary glands (notably to the submandibular glands) and to the oral cavity. CONCLUSION: An improvement over time in xerostomia, occurring in tandem with rising salivary production from the spared major salivary glands, suggests a long-term clinical benefit from their sparing. The oral cavity mean dose, representing RT effect on the minor salivary glands, was found to be a significant, independent predictor of xerostomia. Thus, in addition to the major salivary glands, sparing the uninvolved oral cavity should be considered as a planning objective to further reduce xerostomia.