Biomedical subjects

Patrick Bradshaw

Publications and source records attributed to Patrick Bradshaw.

13 recordsLinked to original sources

PubMed2006

Linear accelerator radiosurgery for vestibular schwannomas.

OBJECT: Radiosurgery has become a popular treatment for small vestibular schwannomas (VSs). The aim of this study was to review an extensive, single-institution experience with linear accelerator (LINAC) radiosurgery for VSs. METHODS: Between July 1988 and August 2005, 390 patients with VSs were treated with LINAC-based radiosurgery at the authors' institution. Patient and treatment variables were prospectively maintained in a computer database. Outcomes were tracked through periodic clinical examinations and annual scanning studies. Multivariate and actuarial statistics were used to analyze rates of local tumor control and complications, including facial and trigeminal neuropathies, after treatment. One- and 2-year actuarial control rates were both 98%, and the 5-year actuarial control rate was 90%. Only four patients (1%) required surgery for tumor growth. Seventeen patients (4.4%) reported facial weakness and 14 patients (3.6%) reported facial numbness after radiosurgery. The risk of these complications rose with increasing tumor volume or increasing radiosurgical dose to the tumor periphery. Since 1994, when doses were deliberately lowered to 1250 cGy, only two patients (0.7%) have experienced facial weakness and two (0.7%) have experienced facial numbness. CONCLUSIONS: Radiosurgery provides a safe and effective therapeutic alternative to surgery for small VSs.

Adult↗

PubMed2005

The association of body mass index and prostate-specific antigen in a population-based study.

BACKGROUND: Recent studies of men with prostate carcinoma suggest that obesity may be associated with more advanced-stage disease and lower overall survival rates. One possible link between body mass index (BMI) and prostate carcinoma prognosis may be disease ascertainment. Prostate-specific antigen (PSA) is widely used to screen for prostate carcinoma. METHODS: The authors examined the association between BMI and PSA in a population-based study of 2779 men without prostate carcinoma. Between 2001 and 2004, these men were enrolled in a study sponsored by the San Antonio Center of Biomarkers of Risk, a clinical and epidemiologic center of the Early Detection Research Network of the National Cancer Institute. RESULTS: The mean PSA value decreased in a linear fashion with an increase in BMI category, from 1.01 ng/mL in normal weight men to 0.69 ng/mL in obese (Class III) men, after adjusting for race/ethnicity and age. CONCLUSIONS: Lower levels of PSA in obese and overweight men could mask biologically consequential prostate carcinoma.

Adult↗

PubMed2005

Radiosurgery in the treatment of malignant gliomas: the University of Florida experience.

OBJECTIVE: To review a single-institution's 12-year experience of treating malignant gliomas with linear accelerator-based radiosurgery. METHODS: One hundred patients were treated for malignant gliomas at the University of Florida between May 1, 1989, and June 12, 2002. Patient variables were entered into a radiosurgery database in a prospective manner. The endpoint of the study was length of survival from the time of diagnosis. The minimum length of follow-up was 18 months or until death. In an attempt to control for selection bias, we used the Radiation Oncology Therapy Group's (RTOG) recursive partitioning categories to compare survival in our group of radiosurgically boosted patients with the RTOG historical database. RESULTS: Recursive partitioning analysis classification was significantly associated with survival. Compared with historical controls, this cohort of patients demonstrated a decreased survival for recursive partitioning analysis Class I and II patients, similar survival for Class III and IV patients, and increased median survival for Class V patients. Other variables demonstrating a statistically significant impact on survival were eloquent location and recurrent disease. CONCLUSION: The results of this study and those of RTOG 93-05 suggest that the reported benefit of upfront radiosurgical boost for malignant gliomas is the result of selection bias. The possibility remains that radiosurgical boost is of benefit in recurrent tumors, especially those in RTOG Class V.

Adult↗

PubMed2005

Linear accelerator surgery for meningiomas.

OBJECT: In this paper the authors review the results of a single-center experience in the use of linear accelerator (LINAC) surgery for radiosurgical treatment of meningiomas. METHODS: A retrospective analysis of all patients treated with LINAC surgery for meningiomas between May 1989 and December 2001 was performed. All patients participated in follow-up review for a minimum of 2 years, and no patients were excluded. Two hundred ten patients were treated during the study interval. The actuarial local control rate for benign tumors was 100% at both 1 and 2 years, and 96% at 5 years. The actuarial local control rate for atypical tumors was 100% at 1 year, 92% at 2 years, and 77% at 5 years; and that for malignant tumors was 100% at both 1 and 2 years, and only 19% at 5 years. Of the 210 patients 13 (6.2%) experienced temporary radiation-induced complications, and only five (2.3%) experienced permanent complications. In all patients with a permanent complication the histological characteristics of the meningioma were malignant. CONCLUSIONS: Linear accelerator surgery produced high local control rates and very low rates of permanent morbidity in patients harboring benign meningiomas.

Adult↗

PubMed2004

Early prostate-specific antigen (PSA) kinetics following prostate carcinoma radiotherapy: prognostic value of a time-and-PSA threshold model.

BACKGROUND: The goal of the current study was to analyze the prognostic value of early prostate-specific antigen (PSA) kinetics, with PSA assessed as reaching or failing to reach discrete threshold values at fixed time points during follow-up after external-beam radiotherapy (EBRT) for prostate carcinoma. METHODS: The authors conducted a retrospective review of PSA follow-up for 839 patients treated between May 1987 and December 2000 at the Cleveland Clinic Foundation (Cleveland, OH). They also assessed the impact on bRFS of PSA levels lower than defined threshold values at given time points during follow-up. RESULTS: During a median follow-up of 74 months (range, 24-189 months), 540 patients (64.4%) maintained bRFS, whereas 299 patients (35.6%) did not maintain bRFS. The median nadir among patients with sustained bRFS was 0.4 ng/mL, with a median time to nadir of 28.9 months. Patients who did not maintain bRFS reached a median nadir of 1.3 ng/mL at a median of 15 months (P < 0.0001 for both nadir level and time to nadir). Reaching PSA thresholds of 3.0, 2.0, 1.0, 0.5, and 0.2 ng/mL at any time during follow-up was correlated with improved bRFS (P < 0.0001, each threshold). Patients whose PSA levels crossed the appropriate thresholds within 3 and 6 months of follow-up, irrespective of the time or level of eventual nadir, exhibited significantly improved bRFS when compared with patients whose PSA levels reached those thresholds at any time during follow-up and patients whose PSA levels never reached those thresholds (all thresholds: P < 0.0001). CONCLUSIONS: Despite previous conclusions that early PSA assessment may lack prognostic value, the data obtained in the current study suggest that the kinetics of early PSA decline is predictive of long-term bRFS when assessed using a time-and-PSA threshold model. After EBRT for prostate carcinoma, PSA levels below various discrete PSA thresholds were indicative of statistically meaningful long-term outcome differences between experimental arms as early as 90 days after radiotherapy. If the time-and-PSA threshold model is shown to be predictive of prostate carcinoma mortality as well, then it may allow the scientific community to evaluate promising treatment concepts and technologies at a highly accelerated pace.

Adenocarcinoma↗

PubMed2004

The infectious disease profile of Texas prison inmates.

PURPOSE: Prison inmates present with higher rates of disease morbidity and mortality than the general population. The rates of certain infectious diseases such as hepatitis C, HIV/AIDS, and tuberculosis are reported to be particularly elevated in prison systems. Scarce information, however, exists on the overall infectious disease profile of inmate populations. The present study examined the prevalence of major infectious diseases in one of the nation's largest prison populations. METHODS: The study population consisted of 336,668 Texas Department of Criminal Justice (TDCJ) inmates who were incarcerated for any duration between January 1, 1999 and December 31, 2001. Information on medical conditions, sentencing factors, and sociodemographic factors was obtained from an institution-wide medical information system. RESULTS: Latent tuberculosis infection constituted the most prevalent infectious disease reported among inmates. This was followed in frequency by hepatitis C, HIV/AIDS, and syphilis. Prevalence estimates for most of the infectious diseases under study exhibited substantial differences across gender, age, and ethnicity. CONCLUSION: The present study shows that the prison population had prevalence rates that were substantially higher for latent TB, HIV/AIDS, and hepatitis C than those reported for the general population and some incarcerated populations. The rate of active TB among TDCJ inmates, however, was comparable to that of the general population and other incarcerated populations.

Adolescent↗

PubMed2004

Linear accelerator radiosurgery in the treatment of brain metastases.

OBJECTIVE: To review a 12-year experience treating metastatic brain disease with linear accelerator-based stereotactic radiosurgery (SRS). METHODS: We performed a retrospective analysis of all patients treated between 1989 and 2001 with linear accelerator radiosurgery for brain metastases. Patients were followed up both clinically and with imaging studies to document local control, regional control, and survival. Demographic data, dosing parameters, number of lesions, histology, history of whole-brain radiation therapy, and other factors were obtained prospectively. Cox proportional-hazards regression with multivariate and univariate analysis was performed with Stata 8.0 software. RESULTS: A total of 383 patients received SRS for brain metastases during the study interval. Median survival was 9 months. Patients with tumor-type melanoma or multiple metastatic lesions had decreased survival. Actuarial 1-year local control was 75%. Differences in regional control rates were not statistically significant between patients treated with SRS and whole-brain radiation therapy versus SRS alone. CONCLUSION: Radiosurgery is an effective and safe method for treating selected patients with brain metastases.

Adult↗

PubMed2004

Do the morphological characteristics of arteriovenous malformations affect the results of radiosurgery?

OBJECT: The authors sought to determine which morphological features of arteriovenous malformations (AVMs) are statistically predictive of preradiosurgical hemorrhage, postradiosurgical hemorrhage, and neuroimaging-defined failure of radiosurgical treatment. In addition, correlation between computerized tomography (CT) scanning and angiography for the identification of AVM structures was investigated. METHODS: Archived CT dosimetry and available angiographic and clinical data for 268 patients in whom AVMs were treated with linear accelerator radiosurgery were retrospectively reviewed. Many of the morphological features of AVMs, including location, volume, compact or diffuse nidus, neovascularity, ease of nidus identification, number of feeding arteries, location (deep or superficial) of feeding arteries, number of draining veins, deep or superficial venous drainage, venous stenoses, venous ectasias, and the presence of intranidal aneurysms, were analyzed. In addition, a number of patient and treatment factors, including patient age, presenting symptoms, radiation dose, repeated treatment, and radiological outcome, were subjected to multivariate analyses. Two hundred twenty-seven patients were treated with radiosurgery for the first time and 41 patients underwent repeated radiosurgery. Eighty-one patients presented with a history of AVM hemorrhage and 91 patients had AVMs in a periventricular location. Twenty-six patients (10%) experienced a hemorrhage following radiosurgery. Of the 268 patients, 81 (30%) experienced angiographically defined cures, and 37 (14%) experienced MR imaging-defined cures. Eighty-six patients (32%) experienced neuroimaging-defined treatment failure, and 64 underwent insufficiently long follow up. A larger AVM volume (odds ratio [OR] 0.349; p = 0.004) was associated with a decreased rate of pretreatment hemorrhage, whereas periventricular location (OR 6.358; p = 0.000) was associated with an increased rate of pretreatment hemorrhage. None of the analyzed factors was predictive of hemorrhage following radiosurgery. A higher radiosurgical dose was strongly correlated with neuroimaging-defined success (OR 3.743; p = 0.006), whereas a diffuse nidus structure (OR 0.246; p = 0.008) and associated neovascularity (OR 0.428; p = 0.048) were each associated with a lower neuroimaging-defined cure rate. A strong correlation between CT scanning and angiography was noted for both nidus structure (p = 0.000; Fisher exact test) and neovascularity (p = 0.002; Fisher exact test). CONCLUSIONS: Patients presenting with AVMs that are small or periventricular were at higher risk for experiencing hemorrhage. A higher radiosurgical dose correlated strongly with neuroimaging-defined success. Patients in whom the AVM had a diffuse structure or associated neovascularity were at higher risk for neuroimaging-defined failure of radiosurgery. A strong correlation between CT scanning and angiography in the assessment of AVM structure was demonstrated.

Adolescent↗

PubMed2003

Comparing longitudinal binary outcomes in an observational oral health study.

Observational studies continue to be recognized as viable alternatives to randomized trials when making treatment group comparisons, in spite of drawbacks due mainly to selection bias. Sample selection models have been proposed in the economics literature, and more recently in the medical literature, as a method to adjust for selection bias due to observed and unobserved confounders in observational studies. Application of these models has been limited to cross-sectional observational data and to outcomes that are continuous in nature. In this paper we extend application of these models to include longitudinal studies and binary outcomes. We apply a two-stage probit model using GEE to account for correlated longitudinal binary chewing difficulty outcomes. Chewing difficulty was measured every six months during a 24-month period between two groups of subjects: those either receiving or not receiving dental care. Dental care use was measured at six-month intervals as well. Results from our proposed model are compared to results using a standard GEE model that ignores the potential selection bias introduced by unobserved confounders. In this application, accounting for selection bias made a major difference in the substantive conclusions about the outcomes of interest. This is due in part to an adverse selection phenomenon in which those most in need of treatment (and consequently most likely to benefit from it) are actually the ones least likely to seek treatment. Our application of sample selection models to binary longitudinal observational outcome data should serve as impetus for increased utilization of this promising set of models to other health outcomes studies.

Dental Health Services↗

PubMed2003

The association of psychiatric disorders and HIV infection in the correctional setting.

PURPOSE: Psychiatric disorders, such as bipolar disorder, schizophrenia, and depression, have been associated with both HIV-associated risk behaviors and HIV infection. While the US prison population is reported to exhibit elevated rates of HIV/AIDS and most psychiatric disorders, scarce information currently exists on the association of these conditions in the prison setting. The present study examined the association of six major psychiatric disorders with HIV infection in one of the nation's largest prison populations. METHODS: The study population consisted of 336,668 Texas Department of Criminal Justice inmates who were incarcerated for any duration between January 1, 1999 and December 31, 2001. Information on medical conditions and sociodemographic factors was obtained from an institution-wide medical information system. RESULTS: Inmates diagnosed with HIV infection exhibited elevated rates of major depression, dysthymia, bipolar disorder, schizophrenia, schizoaffective disorder, and non-schizophrenic psychotic disorder. These rates persisted in stratified analyses and in a multivariate analysis that statistically adjusted for gender, race, and age category. CONCLUSION: The present cross-sectional study's finding of a positive association between HIV infection and psychiatric diagnoses among inmates holds both clinical and public health relevance. It will be important for future investigations to prospectively assess the underlying mechanisms of these associations in the correctional setting.

Adolescent↗

PubMed2003

Analysis of factors predictive of success or complications in arteriovenous malformation radiosurgery.

OBJECTIVE: This study was undertaken to determine which factors were statistically predictive of radiological and clinical outcomes in the radiosurgical treatment of arteriovenous malformations (AVMs). METHODS: The computerized dosimetric and clinical data for 269 patients were reviewed. The AVM nidus was hand-contoured on successive enhanced computed tomographic slices through the nidus, to allow detailed determinations of nidus volume, target miss, normal brain tissue treated, dose conformality, and dose gradient. In addition, a number of patient and treatment factors, including Spetzler-Martin grade, presenting symptoms, dose, number of isocenters, radiological outcome, and clinical outcome, were subjected to multivariate analysis. RESULTS: Two hundred twenty-five patients were treated with radiosurgery for the first time, and 44 patients underwent radiosurgical retreatment. One hundred forty-three patients had AVMs located in or near "eloquent" brain areas and 126 patients did not. Seventy patients demonstrated preoperative neurological findings related to the AVM and 199 did not. Twenty-six patients had previously undergone endovascular treatment and 10 patients had previously undergone surgical treatment of their AVMs. Of the 269 patients studied, 228 experienced no complication, 10 (3.7%) experienced a transient radiation-induced complication, 3 (1%) experienced a permanent radiation-induced complication, and 28 (10%) experienced posttreatment hemorrhage. CONCLUSION: None of the analyzed factors was predictive of hemorrhage after radiosurgery in this study. The 12-Gy volume was predictive of permanent radiation-induced complications. Eloquent AVM location and 12-Gy volume were correlated with the occurrence of transient radiation-induced complications. Better conformality was correlated with a reduced incidence of transient complications. Lower Spetzler-Martin grades, higher doses, and steeper dose gradients were correlated with radiological success.

Brain Damage, Chronic↗

PubMed2002

Relationships between welfare status, health insurance status, and health and medical care among children with asthma.

OBJECTIVES: This study evaluated the relationships between health insurance and welfare status and the health and medical care of children with asthma. METHODS: Parents of children with asthma aged 2 to 12 years were interviewed at 6 urban clinical sites and 2 welfare offices. RESULTS: Children whose families had applied for but were denied welfare had more asthma symptoms than did children whose families had had no contact with the welfare system. Poorer mental health in parents was associated with more asthma symptoms and higher rates of health care use in their children. Parents of uninsured and transiently insured children identified more barriers to health care than did parents whose children were insured. CONCLUSIONS: Children whose families have applied for welfare and children who are uninsured are at high risk medically and may require additional services to improve health outcomes.

Adult↗

PubMedDate not supplied

Outcomes from stroke rehabilitation in Veterans Affairs rehabilitation units: detecting and correcting for selection bias.

This paper addresses the issue of statistical selection bias in multivariate models of functional gain estimated from observational data. Stroke patients from 20 high-volume Veterans Affairs Medical Centers (VAMCs) with acute and subacute inpatient rehabilitation treatment units were observed. Their gains in overall, motor, and cognitive functional status were measured with the use of the Functional Independence Measure (FIM). In estimating multivariate models of FIM gain during rehabilitation using these observational data, we found statistically significant evidence of selection bias, along with considerable differences in inferences between standard multivariate analyses and our selectivity-corrected models. Our results demonstrate the importance of detecting and correcting for statistical selection bias when one uses nonexperimental data to study gains in functional status.

Activities of Daily Living↗