Development of a Screening Nomogram for Regional Lymph Node Metastasis Development in Muscle Invasive Bladder Cancer after Multiagent Systemic Therapy

PURPOSE/OBJECTIVE(S)

A reliable method of identifying clinically node negative bladder cancer patients at greater risk of developing lymph node metastasis and may require intensified therapy is needed. The purpose of this study was to create a nomogram to quantify the risk for regional lymphatic involvement in non-metastatic muscle invasive bladder cancer.

MATERIALS/METHODS

Usingthe National Cancer Database, patients with clinical T2-4N0M0 urothelial carcinoma of the bladder between the years of 2004 - 2020 were selected. All patients completed multiagent chemotherapy followed by surgery for pathologic nodal staging to determine presence or absence of nodal disease. No neoadjuvant radiation therapy was allowed and patients with history of prior malignancies were excluded. Following a 70:30 training to testing data split, baseline variables were assessed using univariate logistic regression. Variables were selected for inclusion in the multivariate logistic regression model using a combination of previously reported findings in the literature and/or if found to have a p-value < 0.05 on univariate analysis. A nomogram was constructed using this final model with assessment using calibration plots and the area under the receiver operating characteristics curve (AUC), respectively. An empiric cut point was chosen at 95% sensitivity to identify patients at "high" and "low" risk for pathologic nodal disease with overall assessment in both cohorts using chi-square.

RESULTS

A total of 6194patients were identified for study with a median age of 65 years (IQR = 58 - 71 years). Most patients were male (68.0%) with T2 disease (81.2%). The final multivariate model included age at time of diagnosis (OR = 0.99; 95% CI = 0.99 - 1.00; p = 0.172), time from diagnosis to initiation of chemotherapy (OR = 1.00; 95% CI = 1.00 - 1.01; p = 0.005), papillary histology (OR = 0.85; 95% CI = 0.72 - 1.01; p = 0.068), and clinical T stage (Table 1). Model calibration demonstrated excellent goodness-of-fit with good discrimination (AUC = 0.644). Within the training data, high risk patients were seen to have a twofold increase in pathologic nodal disease (N = 835/3924, 21.2%) when compared to those identified as low risk (N = 38/347, 9.9%) (p < 0.001). Validation within the testing data set demonstrated similar results with pathologic node rates of 22.8% and 7.8% for high- and low-risk patients, respectively (AUC = 0.645, p < 0.001).

CONCLUSION

This study demonstrates a clinically applicable risk stratification tool for identifying patients at risk for developing lymphadenopathy in T2-4 bladder cancer and may help guide future research in selecting patients eligible for escalation of therapy. Future studies should aim to externally validate this tool within prospective cohorts, and seek to determine if this nomogram may provide further prognostic utility.

Prognostication of Overall Survival in Muscle Invasive Bladder Cancer: An Application of a Lymph Node Metastasis Nomogram

PURPOSE/OBJECTIVE(S)

The purpose of this study was to determine if a previously developed nomogram predictive of developing pathologic lymph node metastasis after multiagent chemotherapy for clinical node-negative muscle invasive bladder cancer may also prognosticate overall survival (OS) in patients treated with definitive chemoradiotherapy (CRT).

MATERIALS/METHODS

Using the National Cancer Database, we identified all patients with cN0 muscle invasive urothelial carcinoma of the bladder treated with definitive CRT from 2004 to 2020. Patient probability of occult nodal disease was assessed using a previous nomogram developed from those treated with multiagent chemotherapy alone followed by pathologic nodal assessment. Following a 70:30 training and testing data split, variables were assessed for association with OS using the log-rank test, with those with p < 0.05 deemed eligible for inclusion within a multivariate Cox proportional hazards model. Patients were then stratified as high-, medium-, or low-risk for death using the hazard function's prognostic index. The proportional hazards assumption was checked using Schoenfeld residuals and discrimination assessed using dynamic area under the receiver operating characteristics curves (AUC). Validation was assessed within the testing and a retrospectively collected institutional cohort of 15 patients treated from 2014 - 2020 with CRT.

RESULTS

A total of 1047 patients were identified for this study with median age of 78 years (IQR = 70-83 years) and follow-up of 31.3 months (IQR = 16.0 - 56.6 months). Cox analysis revealed patient age (HR = 1.03; 95% CI = 1.02 - 1.04; p < 0.001), Charlson-Deyo Score, and predicted probability of developing future lymphadenopathy (HR = 4.47; 95% CI = 1.83 - 10.93; p = 0.001) were significantly associated with OS. Median OS for those identified as high, medium, and low risk for death on Cox analysis was 34.2 months (IQR = 21.3 - 40.6 months), 38.9 months (IQR = 31.4 - 47.2 months), and 77.8 months (IQR = 56.1 - 100.3 months), respectively (AUC range = 0.615 - 0.870) (p < 0.001). Similar discrimination was seen within the testing cohort as well with significant differences between median OS across each group (AUC range = 0.580 - 0.726) (p < 0.001). Notably, among patients within the institutional cohort, only one patient stratified as high (N = 1/2; 50.0%) or medium risk (N = 0/5; 0.0%) remained alive at time of final follow-up, whereas 88.9% (N = 7/8) of low-risk patients survived (p = 0.051). Similarly, significant differences in OS were again seen between risk groups, with a median OS of 51.3 months and 19.9 months for high- and medium-risk patients, respectively, while median OS for low-risk patients was not reached (p = 0.006).

CONCLUSION

This study demonstrates the prognostic utility of a previously reported nomogram in predictions of OS. Investigation is warranted to explore how radiation and chemotherapy may offset worse OS in those at high risk for occult nodal disease progression.

Occlusive and Proliferative Properties of Different Collagen Membranes-An In Vitro Study

Different collagen barrier membranes come in various sources and crosslinking that may affect barrier function and tissue integration. This study investigated barrier function and tissue integration of the three different collagen membranes (Jason^®: porcine pericardium, GENOSS: bovine tendon, and BioMend^® Extend: cross-linked bovine tendon) with human gingival fibroblasts. The barrier function and tissue integration properties were determined under confocal microscopy. Morphological characteristics were observed using scanning electron microscopy. Our results showed that all collagen membranes allowed a small number of cells to migrate, and the difference in barrier function ability was not significant. The cross-linked characteristics did not improve barrier ability. The native collagen membrane surfaces allowed evenly scattered proliferation of HGF, while the cross-linked collagen membrane induced patchy proliferation. Statistically significant differences in cell proliferation were found between Jason and BioMend Extend membranes (p = 0.04). Scanning electron microscope showed a compact membrane surface at the top, while the bottom surfaces displayed interwoven collagen fibers, which were denser in the crosslinked collagen membranes. Within the limitations of this study, collagen membranes of different origins and physical properties can adequately prevent the invasion of unwanted cells. Native collagen membranes may provide a better surface for gingival cell attachment and proliferation.

Revisiting CT Signs of Unilateral Vocal Fold Paralysis: A Single, Blinded Study

BACKGROUND AND PURPOSE

Several CT findings are thought to be indicative of vocal cord paralysis; however, these signs have never been validated in a blinded fashion. This study attempts to compare and validate these signs and determine their accuracy in predicting vocal cord paralysis.

MATERIALS AND METHODS

A retrospective chart review was performed, and CT scans from patients with known unilateral vocal cord paralysis and known normal vocal cord movement were reviewed by 3 radiologists who were blinded to the status of the patients' laryngeal function. The scans were reviewed and scored for 8 accepted signs of vocal cord paralysis as well as for predicting a final diagnostic conclusion. Statistical analysis using odds ratios for signs and the Fleiss κ for criterion agreement among the radiologists was performed for diagnostic accuracy.

RESULTS

The presence of medial displacement of the posterior ipsilateral vocal fold margin and ipsilateral laryngeal ventricular dilation yielded the greatest positive predictive value. Other signs demonstrated high specificity, but interrater discrepancy was greater than expected and diminished the reliability of these signs in predicting vocal cord paralysis. Overall, sensitivity and negative predictive values were low.

CONCLUSIONS

Predicting vocal cord paralysis on the basis of CT findings is not as accurate or straightforward in prospectively predicting vocal cord paralysis as implied in prior studies.

Sex, Sleep, Steroids, and Lifestyle: Unraveling the Coronavirus Disease 2019 Conundrum

Coronavirus disease 2019 (COVID-19) has wreaked havoc and distressed economies worldwide. Countries have gone on lockdown of their economies to prevent the spread of the disease. This obviously led to collateral damage in the form of worsening healthcare for non-COVID-related conditions and is playing havoc with the world economy. Herein, we suggest novel strategies to prevent COVID-19 related complications, keeping in view the pathophysiology of the disease.

A UNIQUE CASE OF CENTRAL HYPOPITUITARISM AND CENTRAL DIABETES INSIPIDUS CAUSED BY DIFFUSE LARGE B-CELL LYMPHOMA

OBJECTIVE

To present the case of a 39-year-old male admitted to the hospital with diabetes insipidus as a sequela of a previously undiagnosed diffuse large B-cell lymphoma. This case is unique, as the patient's disease was determined to be an infiltrative malignancy affecting the pituitary infundibular stalk, resulting in multifocal pituitary dysfunction.

METHODS

Case report.

RESULTS

Initially presenting with gastrointestinal bleed, later discovered to be from tumor infiltration of gastric vessels, diagnosis of lymphoma was made when gastrectomy became necessary for hemostasis. Subsequent hypernatremia on basic laboratory studies led to further investigation and revealed central diabetes insipidus. Magnetic resonance imaging of the pituitary was performed, showing thickening of the infundibular stalk. Additional endocrine evaluation revealed central hypothyroidism and central adrenal insufficiency.

CONCLUSION

Radiologic findings of thickened pituitary infundibulum can support the diagnosis of central diabetes insipidus when additional symptoms are present. Central diabetes insipidus due to lymphomatous infundibular stalk infiltration is an uncommon presentation of endocrine deficiency as well as malignancy; this case demonstrates the management of a critically ill patient with central hypopituitarism due to diffuse B-cell lymphoma.

Urgent Need to Define Pretreatment Predictors of Immune Check Point Inhibitors Related Endocrinopathies: A Case Report and Review of Literature

Immune check point inhibitors have revolutionized the treatment of metastatic malignancies. They are a promising area in oncology and more drugs are likely to be available in the coming years. Along with the promise of better response oncologically, there is an increased incidence of endocrinopathies related to autoimmunity. This case report illustrates the dramatic development of hypothyroidism in a patient with underlying subclinical hyperthyroidism. It also suggests the potential pretreatment predictors of endocrinopathies related to these immune check point inhibitors.

Clinical conundrums in management of sepsis in the elderly

In 2012, surviving sepsis campaign came out with updated international guidelines for management of severe sepsis and septic shock. Paradoxically, there are no specific guidelines for management of sepsis in the elderly, although the elderly are more predisposed to sepsis, and morbidity and mortality related to sepsis. Sepsis in the elderly is, more often than not, complicated by clinical conundrums such as congestive heart failure (CHF), atrial fibrillation (AF), chronic kidney disease (CKD), acute kidney injury (AKI), delirium, dementia, ambulatory dysfunction, polypharmacy, malglycemia, nutritional deficiencies, and antibiotic resistance. Also, with recurrent admissions to the hospital and widespread use of antibiotics, the elderly are more susceptible to Clostridium difficile colitis.

Efficacy of noninvasive ventilation after planned extubation: A systematic review and meta-analysis of randomized controlled trials

The objective our meta-analysis is to update the evidence on the efficacy of noninvasive ventilation (NIV) compared with conventional oxygen therapy after planned extubation. We did a systematic literature review of database, including Pubmed, EMBASE, and Cochrane. We included randomized controlled trials comparing NIV with conventional oxygen therapy after planned extubation in medical intensive care unit (ICU) in our analysis. The results of our meta-analysis is consistent with the results of previous reviews and show that NIV decreased reintubation rate significantly as compared to conventional oxygen therapy in chronic obstructive pulmonary disease (COPD) and patients at high risk for extubation failure; COPD (RR, 0.33; 95% CI, 0.16-0.69; I2 = 0), high risk (RR, 0.47; 95% CI, 0.32-0.70; I2 = 0). However, in a mixed medical ICU population, there was no statistical difference of reintubation rate between the two groups (RR, 0.66; 95% CI, 0.25-1.73; I2 = 68%). Our study suggests that use of NIV after planned extubation significantly decreases the reintubation rate in COPD patients and patients at high risk for extubation failure, confirming the findings of previous reviews. There is no difference in the reintubation rate between the two groups in the mixed medical ICU population.

Management of diabetes in the elderly with canagliflozin: A newer hypoglycemic drug on the horizon

Canagliflozin is the first available oral inhibitor of sodium/glucose cotransporter 2 (SGLT2) in the market. At the outset it sounds excellent for the use in the elderly diabetic population, because of its minimal tendency to cause hypoglycemia. However, the clinician needs to exercise caution as it needs to be dosed renally. The clinician needs to be circumspect about potential drug interactions, especially when there is an underlying chronic kidney disease (CKD) and congestive heart failure (CHF). Also its use is best avoided in people who are predisposed to genital mycotic and urinary tract infections (UTI).

Management of diabetes mellitus type-2 in the geriatric population: Current perspectives

The prevalence of diabetes mellitus (DM) has increased exponentially throughout the world and there is rapid increase in elderly diabetics. DM is associated with increased mortality and considerable morbidity including stroke, heart disease, and diminished quality of life in the elderly. However, the unique features of geriatric diabetes have not been given due a prominence in medical literature. Hypoglycemia remains the biggest complicating factor and needs to be avoided in the elderly. Most people in the geriatric age group have some degree of renal insufficiency and medications need to be adjusted wisely with changing renal profile. Because safer and more effective pharmacological therapy is available, an individual approach to DM in the elderly is essential.

Predictors of acute kidney injury in geriatric patients undergoing total knee replacement surgery

BACKGROUND

Few studies have focused on patients' characteristics that affects acute kidney injury (AKI) after total knee replacement surgery (TKR).

OBJECTIVES

The primary objective of this retrospective study was to identify patients' characteristics associated with AKI after TKR.

PATIENTS AND METHODS

Between January 2008 and December 2009, 659 patients with a mean age of 67.1 years (range, 39-99) underwent TKA at Regional Hospital Knee and Hip Institute. Retrospective chart review was done to identify patients' characteristics that were associated with AKI after TKR. Logistic regression was used to evaluate AKI.

RESULTS

AKI occurred in 21.9% of patients. AKI risk decreased between 2008 and 2009 (odds ratio, 0.55; 95% CI, -0.37 to 0.82) but increased with age (P < 0.001), diabetes mellitus (DM), and angiotensin converting enzyme inhibitors (ACEI)/angiotensin receptor blockers (ARB) use (OR, -1.6; 95% CI, -1.0 to 2.5; and OR, -1.5, 95% CI, -1.0 to 2.3, respectively). However, the effects of DM and ACEI/ARB use were not independent; when both were included in the regression model, neither was statistically significant, and both ORs were smaller than combined OR.

CONCLUSIONS

When examined separately, both DM and preoperative ACEI/ARB use increased the risk of AKI; however these factors were correlated and were not independent predictors of significantly increased risk. Patients with DM have higher tendency to develop AKI and hence, preoperative renal risk stratification should be done in all patients with DM.

Hypoglycaemia in anesthesiology practice: Diagnostic, preventive, and management strategies

Diabetes mellitus has emerged as one of the fastest growing non communicable diseases worldwide. Management of diabetic patients during surgical and critically illness is of paramount challenge to anesthesiologist and intensivist. Among its major acute complications, hypoglycemia has been given lesser attention as compared to other major acute complications; diabetic ketoacidosis and hyperosmolar non ketotic coma. However, newer studies and literary evidence have established the serious concerns of morbidity and mortality, both long- and short-term, related to hypoglycemia. basis. Invariably, diabetic patients are encountered in our daily routine practice of anesthesia. During fasting status as well as the perioperative period, it is hypoglycemia that is of high concern to anesthesiologist. Management has to be based on clinical, pharmacological, social, and psychological basis, so as to completely prevent the complications arising from an acute episode of hypoglycemia. This review aims to highlight various aspects of hypoglycemia and its management both from endocrine and anesthesia perspective.

Expanding giant right coronary artery aneurysm: an acute need for new management strategies

Angiography use has become increasingly common worldwide. Coronary artery aneurysm may be an incidental finding during angiography. Occasionally it might be symptomatic or may become symptomatic over the course of time. Rupture of aneurysm may lead to disastrous complications. Here we present a case in which aneurysm was asymptomatic but surgical intervention was done because of rapid increase in the size of aneurysm. This is to drive home the point that timely surgical intervention is instrumental in preventing complications associated with possible rupture of the aneurysm.

Polypharmacy and potentially inappropriate medication use as the precipitating factor in readmissions to the hospital

Background and Aim:

Readmission to the hospital within 30 days of discharge from the hospital is a common occurrence. Congestive heart failure is the most common cause of readmissions in the hospital. We hypothesized that irrespective of the admission diagnosis polypharmacy and potentially inappropriate use of medications (PIM) leads to readmissions within 30 days of discharge from the hospital.

Materials and Methods:

A retrospective study was carried out by reviewing the hospital records of 414 patients who were readmitted to the hospital within 30 days of discharge from the hospital between January 2008 and December 2009. The data was stratified to see which patients were on polypharmacy and/or on PIM. Polypharmacy was defined as use of more than 5 medications. PIM was defined as per the modified Beers criteria. Day 0 was defined as the day of discharge and day1 was defined as the day-after Admission to the hospital. Statistical analysis was carried out using a two-way analysis of variance (ANOVA) on the data to see if polypharmacy and/or PIM was related to readmission within 30 days of discharge irrespective of admission diagnosis.

Results:

Polypharmacy was related to hospital readmission at day 1 and day 0, however inappropriate drug use was found to be not related at any day. Polypharmacy and PIM combined had a positive correlation to readmission only on days 1 and 0 and it was statistically significant. The use of minimal and appropriate use of drugs was statistically significant compared to polypharmacy and PIM use.

Conclusions:

Polypharmacy and PIM are under recognized cause of readmissions to the hospital.

Clinical conundrums in management of hypothyroidism in critically ill geriatric patients

CONTEXT

Articles in various international and national bibliographic indices were extensively searched with an emphasis on thyroid and hypothyroid disorders, hypothyroidism in elderly hospitalized patients, hypothyroidism in critically ill geriatric population, thyroxine in elderly hypothyroid, drug interactions and thyroid hormones, and thyroid functions in elderly.

EVIDENCE ACQUISITION

Entrez (including PubMed), NIH.gov, Medscape.com, WebMD.com, MedHelp.org, Search Medica, MD consult, yahoo.com, and google.com were searched. Manual search was performed on various textbooks of medicine, critical care, pharmacology, and endocrinology.

RESULTS

Thyroid function tests in elderly hospitalized patients must be interpreted with circumspection. The elderly are often exposed to high iodide content and critical care settings. This may occur because of either decreased iodine excretion or very high intake of iodine. This is especially true for elderly population with underlying acute or chronic kidney diseases or both. Amiodarone, with a very high iodine content, is also often used in this set of population. Moreover, other medications including iodinated contrast are often used in the critical care settings. These may affect different steps of thyroid hormone metabolism, and thereby complicate the interpretation of thyroid function tests.

CONCLUSIONS

The current review is aimed at analyzing and managing various clinical aspects of hypothyroidism in hospitalized elderly, and critically ill geriatric patients.

New orally active anticoagulants in critical care and anesthesia practice: the good, the bad and the ugly

With the adoption of dabigatran, rivaroxaban, and apixaban into clinical practice, a new era has arrived in the practice of oral anticoagulants. Venous thromboembolism (VTE) has traditionally been underdiagnosed and under treated in Asia. With increasing longevity, the diagnosis and the need for management of atrial fibrillation (AF) and VTE is likely to increase significantly. The new orally active anticoagulants (NOACs) have reasonably filled the lacunae that clinicians traditionally faced when treating patients with vitamin K antagonist (VKA). Unlike VKA, NOACs do not need frequent monitoring. Therefore, more patients are likely to get therapeutic effects of anticoagulation and thus reduce morbidity and mortality associated with VTE and AF. However, the clinicians need to be circumspect and exercise caution in use of these medications. In particular (in geriatric population), the clinicians should look out for drug-drug interactions and underlying renal insufficiency. This would ensure therapeutic efficacy and minimize bleeding complications. Here, it is important to note that the antidote for NOACs is not available and is a major concern if emergency surgical procedure is required in their presence.

Anesthesia and thyroid surgery: The never ending challenges

Thyroidectomy is the most common endocrine surgical procedure being carried out throughout the world. Besides, many patients who have deranged thyroid physiology, namely hyperthyroidism and hypothyroidism, have to undergo various elective and emergency surgical procedures at some stage of their life. The attending anesthesiologist has to face numerous daunting tasks while administering anesthesia to such patients. The challenging scenarios can be encountered at any stage, be it preoperative, intra-op or postoperative period. Preoperatively, deranged thyroid physiology warrants optimal preparation, while anticipated difficult airway due to enlarged thyroid gland further adds to the anesthetic challenges. Cardiac complications are equally challenging as also the presence of various co-morbidities which make the task of anesthesiologist extremely difficult. Thyroid storm can occur during intra-op and post-op period in inadequately prepared surgical patients. Postoperatively, numerous complications can develop that include hemorrhage, laryngeal edema, nerve palsies, tracheomalacia, hypocalcemic tetany, pneumothorax, etc., The present review aims at an in-depth analysis of potential risk factors and challenges during administration of anesthesia and possible complications in patients with thyroid disease.

Anesthetic management of primary hyperparathyroidism: A role rarely noticed and appreciated so far

Endocrine surgeries have been on the rise for the last few years. During surgery, endocrine disorders present unique challenges to the endocrinologist and to the attending anesthesiologist. The endocrine, electrolyte and metabolic disturbances resulting from such disorders can have a profound effect on the normal human physiological milieu. Surgery of parathyroid glands is no exception and is associated with a multiple challenges during pre-, intra-, and post-operative period. Pre-op examination and optimization is essential so as to prevent any intra-op or post-op complications. The most striking electrolyte disturbance during parathyroid surgery is the imbalance of calcium levels in the body and the main emphasis during the entire peri-operative period revolves around the maintenance of normal serum calcium levels. The present article review in depth the various anesthetic considerations and implications during parathyroid surgery with an emphasis on pre-op preparation for elective and emergency surgery.

Coronary artery bypass grafting: a precipitating factor for perioperative diabetic ketoacidosis

Non-Insulin Dependent Diabetes Mellitus (NIDDM) is a common disease entity in patients with Coronary Artery Disease (CAD). Diabetic Ketoacidosis (DKA) is not only one of the major complications of Diabetes Mellitus but also a significant challenging clinical entity for the patients undergoing any elective or emergency surgery. Coronary Artery Bypass Grafting (CABG) being done in a patient with DKA has not been reported. We are presenting a rare case with DKA in whom CABG was carried out in a hospital devoted exclusively to cardiac cases. Insulin was given in very large doses as a part of therapeutic regimen and the outcome was favorable. This report concludes that if a patient undergoing urgent cardiac surgery incidentally develops DKA after induction of anesthesia, then the operation can be carried out provided DKA is managed aggressively. Also, major stress factors like cardio pulmonary bypass (CPB) and hypothermia should be avoided and care should be taken to avoid cerebral edema.

Clinical and critical care concerns in severely ill obese patient

The incidence of obesity has acquired an epidemic proportion throughout the globe. As a result, increasing number of obese patients is being presented to critical care units for various indications. The attending intensivist has to face numerous challenges during management of such patients. Almost all the organ systems are affected by the impact of obesity either directly or indirectly. The degree of obesity and its prolong duration are the main factors which determine the harmful effect of obesity on human body. The present article reviews few of the important clinical and critical care concerns in critically ill obese patients.

SU-E-J-102: The Impact of the Number of Subjects for Atlas-Based Automatic Segmentation

PURPOSE

To determine the impact of atlas size on the performance of atlas-based automatic segmentation (ABAS) in delineation of organs at risk for adaptive radiation therapy.

METHODS

A total of 25 patients who had undergone intensity modulated radiation therapy for various head and neck cancers were retrospectively selected for inclusion in a library to be used for ABAS with the MIM VISTA software package (MIM Software, Cleveland OH). Treatment planning computed tomography (CT) scans and subsequent organ at risk (OAR) contours generated as part of the treatment planning process for these patients were added to the library. This library of 25 patients was then successively pruned to generate 5 atlases with 25, 20, 15, 10, and 5 patient subjects respectively. Atlas based segmentation was performed on 10 retrospectively selected treatment planning CT scans to automatically generate right and left parotid glands and brainstem contours. These planning CT scans belonged to a unique set of 10 patient subjects different from the ones used for generating the atlases. One physician (JW), who was blinded to the ABAS results, manually delineated gold-standard contours for the right and left parotid glands and brainstem. Dice similarity coefficients were calculated and analyzed as a function of atlas subject size.

RESULTS

For the sites selected in this study, the performance of ABAS was relatively insensitive to atlas size. Furthermore, some patient subjects were repeatedly selected implying that the adoption of a single standard patient for ABAS may be of benefit.

CONCLUSIONS

Our preliminary results indicate that the performance of the atlas based segmentation module in MIM VISTA Version 5.2 for the organs studied here may be relatively insensitive to the atlas size.

Radioactive bone cement for the treatment of spinal metastases: a dosimetric analysis of simulated clinical scenarios

Vertebral metastases are a common manifestation of many cancers, potentially leading to vertebral collapse and neurological complications. Conventional treatment often involves percutaneous vertebroplasty/kyphoplasty followed by external beam radiation therapy. As a more convenient alternative, we have introduced radioactive bone cement, i.e. bone cement incorporating a radionuclide. In this study, we used a previously developed Monte Carlo radiation transport modeling method to evaluate dose distributions from phosphorus-32 radioactive cement in simulated clinical scenarios. Isodose curves were generally concentric about the surface of bone cement injected into cadaveric vertebrae, indicating that dose distributions are relatively predictable, thus facilitating treatment planning (cement formulation and dosimetry method are patent pending). Model results indicated that a therapeutic dose could be delivered to tumor/bone within ∼4 mm of the cement surface while maintaining a safe dose to radiosensitive tissue beyond this distance. This therapeutic range should be sufficient to treat target volumes within the vertebral body when tumor ablation or other techniques are used to create a cavity into which the radioactive cement can be injected. With further development, treating spinal metastases with radioactive bone cement may become a clinically useful and convenient alternative to the conventional two-step approach of percutaneous strength restoration followed by radiotherapy.

Immune reconstitution following rabbit antithymocyte globulin

Depletional induction therapies are routinely used to prevent acute rejection and improve transplant outcome. The effects of depleting agents on T-cell subsets and subsequent T-cell reconstitution are incompletely defined. We used flow cytometry to examine the effects of rabbit antithymocyte globulin (rATG) on the peripheral T-cell repertoire of pediatric and adult renal transplant recipients. We found that while rATG effectively depleted CD45RA+CD27+ naïve and CD45RO+CD27+ central memory CD4+ T cells, it had little effect on CD45RO+CD27- CD4+ effector memory or CD45RA+CD31-, CD45RO+CD27+ and CD45RO+CD27- CD8+ T cell subsets. When we performed a kinetic analysis of CD31+ recent thymic emigrants and CD45RA+/RO+ T cells, we found evidence for both thymopoiesis and homeostatic proliferation contributing to immune reconstitution. We additionally examined the impact of rATG on peripheral CD4+Foxp3+ T cells. We found that in adults, administration of rATG-induced peripheral expansion and new thymic emigration of T cells with a Treg phenotype, while CD4+Foxp3+ T cells of thymic origin predominated in children, providing the first evidence that rATG induces Treg in vivo. Collectively our data indicate that rATG alters the balance of regulatory to memory effector T cells posttransplant, providing an explanation for how it positively impacts transplant outcome.

Evaluation of a radiation transport modeling method for radioactive bone cement

Spinal metastases are a common and serious manifestation of cancer, and are often treated with vertebroplasty/kyphoplasty followed by external beam radiation therapy (EBRT). As an alternative, we have introduced radioactive bone cement, i.e. bone cement incorporated with a radionuclide. In this study, we present a Monte Carlo radiation transport modeling method to calculate dose distributions within vertebrae containing radioactive cement. Model accuracy was evaluated by comparing model-predicted depth-dose curves to those measured experimentally in eight cadaveric vertebrae using radiochromic film. The high-gradient regions of the depth-dose curves differed by radial distances of 0.3-0.9 mm, an improvement over EBRT dosimetry accuracy. The low-gradient regions differed by 0.033-0.055 Gy/h/mCi, which may be important in situations involving prior spinal cord irradiation. Using a more rigorous evaluation of model accuracy, four models predicted the measured dose distribution within the experimental uncertainty, as represented by the 95% confidence interval of the measured log-linear depth-dose curve. The remaining four models required modification to account for marrow lost from the vertebrae during specimen preparation. However, the accuracy of the modified model results indicated that, when this source of uncertainty is accounted for, this modeling method can be used to predict dose distributions in vertebrae containing radioactive cement.