Nipple-Sparing Mastectomy After Neoadjuvant Chemotherapy: Definitive Results with a Long-Term Follow-Up Evaluation.

BACKGROUND: Nipple-sparing mastectomy (NSM) is increasingly used for women with breast cancer who are not candidates for conservative surgery. The authors previously reported satisfying results with NSM after neoadjuvant chemotherapy (NACT). METHODS: From 2010 to 2020, 1072 women underwent mastectomy at the authors' institution. In this group, 433 NSMs were performed (40%). The only contraindications to NSM were close proximity to the nipple-areola complex (NAC), bloody discharge, and Paget disease. RESULTS: In 112 cases involving 111 women, NSM followed NACT (group 1), whereas it was performed as primary surgery in 321 instances involving 306 women (group 2). At 5 years, local relapse was 7% in group 1 and 2% in group 2, although in the multivariate analysis, locoregional relapses (LRRs) did not differ between the two groups. An increased incidence of local relapse was associated with higher tumor stage (stage III; p = 0.046) and age younger than 51 years (p = 0.038). For 34 (30.3%) of the 111 women in group 1 with a pathologic complete response (pCR), no LRRs were recorded. Only one NAC recurrence was observed. Overall survival with each tumor stage did not differ between the two groups. No differences in complications were observed. Cosmetic results were satisfying in 83.8% of the cases and did not get worse after NACT. CONCLUSIONS: The study data definitively confirm that NSM is safe even after NACT, with good cosmetic results and complications comparable with those in the primary surgery setting. Tumor stage and age were the only independent factors for local relapse. Patients with pCR enjoyed optimal locoregional control.

Heterogeneous alpha-cell population modeling of glucose-induced inhibition of electrical activity.

Glucagon release from the pancreatic alpha-cells is regulated by glucose, but the underlying mechanisms are far from understood. It is known that the alpha-cell population is very heterogeneous, but - compared to the insulin-secreting beta-cells - the consequences of this cell-to-cell variation are much less studied. Since the alpha-cells are not electrically coupled, large differences in the single cell responses are to be expected, and this variation may contribute to the confusion regarding the mechanisms of glucose-induced suppression of glucagon release. Using mathematical modeling of alpha-cells with realistic cell-to-cell parameter variation based on recent experimental results, we show that the simulated alpha-cells exhibit great diversity in their electrophysiological behavior. To robustly reproduce experimental recordings from alpha-cell exposed to a rise in glucose levels, we must assume that both intrinsic mechanisms and paracrine signals contribute to glucose-induced changes in electrical activity. Our simulations suggest that the sum of different electrophysiological responses due to alpha-cell heterogeneity is involved in glucose-suppressed glucagon secretion, and that more than one mechanism contribute to control the alpha-cell populations' behavior. Finally, we apply regression analysis to our synthetic alpha-cell population to infer which membrane currents influence electrical activity in alpha-cells at different glucose levels. The results from such statistical modeling suggest possible disturbances underlying defect regulation of alpha-cell electrical behavior in diabetics. Thus, although alpha-cells appear to be inherently complex and heterogeneous as reflected in published data, realistic modeling of the alpha-cells at the population level provides insight into the mechanisms of glucagon release.

SYK Targeting Represents a Potential Therapeutic Option for Relapsed Resistant Pediatric ETV6-RUNX1 B-Acute Lymphoblastic Leukemia Patients.

The presence of the chromosomal rearrangement t(12;21)(ETV6-RUNX1) in childhood B-acute lymphoblastic leukemia (B-ALL) is an independent predictor of favorable prognosis, however relapses still occur many years later after stopping therapy, and patients often display resistance to current treatments. Since spleen tyrosine kinase (SYK), a cytosolic nonreceptor tyrosine kinase interacting with immune receptors, has been previously associated with malignant transformation and cancer cell proliferation, we aimed to assess its role in ETV6-RUNX1 cell survival and prognosis. We evaluated the effects on cell survival of three SYK inhibitors and showed that all of them, in particular entospletinib, are able to induce cell death and enhance the efficacy of conventional chemotherapeutics. By using reverse phase protein arrays we next revealed that activated SYK is upregulated at diagnosis in pediatric ETV6-RUNX1 patients who will experience relapse, and, importantly, hyperactivation is maintained at a high level also at relapse occurrence. We thus treated primary cells from patients both at diagnosis and relapse with the combination entospletinib + chemotherapeutics and observed that SYK inhibition is able to sensitize resistant primary cells to conventional drugs. Entospletinib could thus represent a new therapeutic option supporting conventional chemotherapy for relapsed ETV6-RUNX1 patients, and these evidences encourage further studies on SYK for treatment of other relapsed resistant acute lymphoblastic leukemia (ALL) subgroups.

Regression models for the restricted residual mean life for right-censored and left-truncated data.

The hazard ratios resulting from a Cox's regression hazards model are hard to interpret and to be converted into prolonged survival time. As the main goal is often to study survival functions, there is increasing interest in summary measures based on the survival function that are easier to interpret than the hazard ratio; the residual mean time is an important example of those measures. However, because of the presence of right censoring, the tail of the survival distribution is often difficult to estimate correctly. Therefore, we consider the restricted residual mean time, which represents a partial area under the survival function, given any time horizon τ, and is interpreted as the residual life expectancy up to τ of a subject surviving up to time t. We present a class of regression models for this measure, based on weighted estimating equations and inverse probability of censoring weighted estimators to model potential right censoring. Furthermore, we show how to extend the models and the estimators to deal with delayed entries. We demonstrate that the restricted residual mean life estimator is equivalent to integrals of Kaplan-Meier estimates in the case of simple factor variables. Estimation performance is investigated by simulation studies. Using real data from Danish Monitoring Cardiovascular Risk Factor Surveys, we illustrate an application to additive regression models and discuss the general assumption of right censoring and left truncation being dependent on covariates. Copyright © 2017 John Wiley & Sons, Ltd.

Integrated likelihoods in parametric survival models for highly clustered censored data.

In studies that involve censored time-to-event data, stratification is frequently encountered due to different reasons, such as stratified sampling or model adjustment due to violation of model assumptions. Often, the main interest is not in the clustering variables, and the cluster-related parameters are treated as nuisance. When inference is about a parameter of interest in presence of many nuisance parameters, standard likelihood methods often perform very poorly and may lead to severe bias. This problem is particularly evident in models for clustered data with cluster-specific nuisance parameters, when the number of clusters is relatively high with respect to the within-cluster size. However, it is still unclear how the presence of censoring would affect this issue. We consider clustered failure time data with independent censoring, and propose frequentist inference based on an integrated likelihood. We then apply the proposed approach to a stratified Weibull model. Simulation studies show that appropriately defined integrated likelihoods provide very accurate inferential results in all circumstances, such as for highly clustered data or heavy censoring, even in extreme settings where standard likelihood procedures lead to strongly misleading results. We show that the proposed method performs generally as well as the frailty model, but it is superior when the frailty distribution is seriously misspecified. An application, which concerns treatments for a frequent disease in late-stage HIV-infected people, illustrates the proposed inferential method in Weibull regression models, and compares different inferential conclusions from alternative methods.

Comparing predictions among competing risks models with time-dependent covariates.

Prediction of cumulative incidences is often a primary goal in clinical studies with several endpoints. We compare predictions among competing risks models with time-dependent covariates. For a series of landmark time points, we study the predictive accuracy of a multi-state regression model, where the time-dependent covariate represents an intermediate state, and two alternative landmark approaches. At each landmark time point, the prediction performance is measured as the t-year expected Brier score where pseudovalues are constructed in order to deal with right-censored event times. We apply the methods to data from a bone marrow transplant study where graft versus host disease is considered a time-dependent covariate for predicting relapse and death in remission.

Lobular breast cancer: same survival and local control compared with ductal cancer, but should both be treated the same way? analysis of an institutional database over a 10-year period.

BACKGROUND: Invasive lobular carcinoma (ILC) is believed to be more often multicentric and bilateral compared with invasive ductal cancer (IDC), leading clinicians to pursue a more aggressive local and contralateral approach. METHODS: Retrospective review of a consecutive cohort of breast cancer patients operated at one institution from January 2000 to January 2010 was performed. Median follow-up was 4 years. RESULTS: There were 171 ILC (14.5%) and 1,011 IDC patients in the study period. Median age (63 vs. 65 years) and tumor diameter (1.7 cm) were similar in the two groups. Diagnoses of ILC were more frequent in the second half of the study period (55/465 vs. 116/662, p<0.01). Multicentricity was reported in 108/1,011 (10.6%) IDC and in 31/171 (18.1%) ILC patients (p<0.01). A positive margin of resection at initial surgery was documented in 71/1,011 (7%) IDC and in 21/171 (12.3%) ILC patients (p<0.001). Although the rate of mastectomy decreased over time in both groups, this was more pronounced for ILC patients (p<0.001). Locoregional control, contralateral cancer, overall survival, disease-free survival, and survival according to diameter, nodal status, and type of surgical intervention did not differ between IDC and ILC. On multivariate analysis, stage of disease and hormone receptor status were associated with disease-free survival, but histology was not. CONCLUSIONS: Although ILC is more often multicentric, bilateral, and associated with a positive margin of resection, local control and survival are similar to IDC. ILC can be treated similarly to IDC with good results.

Phosphoproteomic Analysis Reveals a Different Proteomic Profile in Pediatric Patients With T-Cell Lymphoblastic Lymphoma or T-Cell Acute Lymphoblastic Leukemia.

T-cell lymphoblastic lymphoma (T-LBL) and lymphoblastic leukemia (T-ALL) arise from the transformation of precursor T-cells sharing common morphological and immunophenotypic features. Despite this, T-LBL and T-ALL show different genomic/transcriptomic profiles and whether they represent two distinct disease entities or variant manifestations of the same disease is still a matter of debate. In this work, we performed a Reverse Phase Protein Array study on T-LBL and T-ALL samples and demonstrated that they are characterized by a different phosphoproteomic profile. Indeed, T-LBLs showed the hyperactivation of FAK/ERK1/2 and AKT/mTOR pathways, whereas JAK/STAT pathway was significantly hyperphosphorylated in T-ALLs. Moreover, since the only criteria for discriminating T-LBL from T-ALL is blasts' infiltration below 25% in the bone marrow and lymphoma patients can present with a percentage of blasts close to this cut-off, a biomarker that could help distinguishing the two diseases would be of great help for the clinical diagnosis and treatment decision. Pursuing this aim, we identified a proteomic signature of six proteins whose expression/activation was able to discriminate stage IV T-LBL from T-ALL. Moreover, we demonstrated that AKT hyperphosphorylation alone was able to distinguish stage IV T-LBL from both T-ALL and stage III T-LBL. Concluding, these data demonstrate that T-ALL and T-LBL bear different phosphoproteomic profiles, further sustaining the hypothesis of the two disease as different entities and paving the way for the identification of new biomarkers able to distinguish stage IV T-LBL from T-ALL disease, so far based only on BM involvement criteria.

Necroptosis-driving genes RIPK1, RIPK3 and MLKL-p are associated with intratumoral CD3+ and CD8+ T cell density and predict prognosis in hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is a highly lethal cancer and the second leading cause of cancer-related deaths worldwide. As demonstrated in other solid neoplasms and HCC, infiltrating CD8+ T cells seem to be related to a better prognosis, but the mechanisms affecting the immune landscape in HCC are still mostly unknown. Necroptosis is a programmed, caspase-independent cell death that, unlike apoptosis, evokes immune response by releasing damage-associated molecular factors. However, in HCC, the relationship between the necroptotic machinery and the tumor-infiltrating lymphocytes has not been fully investigated so far. METHODS: We investigated the association between the main necroptosis-related genes, that is, RIPK1, RIPK3, MLKL-p, and CD3+/CD8+ tumor-infiltrating T cell by RNA-seq data analysis in 371 patients with primary HCC from The Cancer Genome Atlas and then by immunohistochemistry in two independent cohorts of HCC patients from Italy (82) and Japan (86). RESULTS: Our findings highlighted the immunogenetic role of necroptosis and its potential prognostic role in HCC: RIPK1, RIPK3 and MLKL-p were found significantly associated with intratumoral CD3+ and CD8+ T cells. In addition, multivariate survival analysis showed that the expression of RIPK1, RIPK3 and MLKL-p was associated with better overall survival in the two independent cohorts. CONCLUSIONS: Our results confirmed the immunogenetic properties of necroptosis (NCP) in human HCC, showing that tumor-infiltrating lymphocytes (TILs) and, specifically, CD8+ T cells accumulate in tumors with higher expression of the necroptosis-related genes. These results suggest the importance of further studies to better assess the specific composition, as well as the functional features of the immune environment associated with a necroptotic signature in order to explore new possible diagnostic and immunotherapeutic scenarios.

Regret and Quality of Life After Mastectomy With or Without Reconstruction.

BACKGROUND: Mastectomy represents a deep burden for women with breast cancer. Very little is known about the psychological consequences over time and the quality of life (QoL) of women so treated, with or without breast reconstruction (BR). PATIENTS AND METHODS: A total of 709 patients underwent mastectomy with or without BR between 2002 and 2012 at one institution. Among 468 surviving patients, a 60-query QoL questionnaire on personal issues including some European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire items was presented either by email, letter, or telephone interview. RESULTS: Of those questioned, 328 patients participated, whereas 140 (30%) declined the invitation or were unavailable. The median age was 63 years (range, 30-93 years). Stage I or II of disease was recorded in 73% of patients. Immediate BR was performed in 168 (51%) of 328 patients. Of the remaining patients, only 7 (4%) of 160 proceeded to delayed BR. Younger women had significantly worse Emotional Functioning and Social Functioning (SF) scores (P < .001), independently of tumor stage, and immediate BR improved that (P = .02). SF score was also worsened by chemotherapy (P = .03). Cognitive Functioning score was independent of age, BR, stage, or adjuvant therapies. Body Image and Sexual Functioning scores improved with BR (P < .03), and age was a strong co-variable (P < .001). On multivariate analysis, immediate BR was correlated with age and preoperative plastic surgery consultation. Some 68 (21%) of 328 patients regretted their decision or were disappointed with their choice regarding BR. CONCLUSIONS: Younger patients with breast cancer report a worse impact on their Emotional Functioning and SF scores after mastectomy, both of which are improved by BR. Reconstructing the breast at the time of mastectomy has a significant impact on Body Image and Sexual Functioning scores. A preoperative plastic surgeon consultation improves the rate of immediate BR, whereas delayed reconstruction is rarely adopted. Some 20% of patients are disappointed in or regret their decision regarding BR. We need to improve our management in consideration of these findings.

Ruxolitinib as a Novel Therapeutic Option for Poor Prognosis T-LBL Pediatric Patients.

Lymphoblastic lymphoma (LBL) is the second most common type of non-Hodgkin lymphoma in childhood, mainly of T cell origin (T-LBL). Although current treatment protocols allow a complete remission in 85% of cases, the second-line treatment overall survival for patients with progressive or relapsed disease is around 14%, making this the major issue to be confronted. Thus, we performed a Reverse Phase Protein Array study in a cohort of 22 T-LBL patients to find reliable disease risk marker(s) and new therapeutic targets to improve pediatric T-LBL patients' outcome. Interestingly, we pinpointed JAK2 Y1007-1008 as a potential prognosis marker as well as a therapeutic target in poor prognosis patients. Hence, the hyperactivation of the JAK1/2-STAT6 pathway characterizes these latter patients. Moreover, we functionally demonstrated that STAT6 hyperactivation contributes to therapy resistance by binding the glucocorticoid receptor, thus inhibiting its transcriptional activity. This was further confirmed by specific STAT6 gene silencing followed by dexamethasone treatment. Finally, JAK1/2-STAT6 pathway inhibition by ruxolitinib, an FDA approved drug, in cell line models and in one T-LBL primary sample led to cell proliferation reduction and increased apoptosis. Globally, our results identify a new potential prognostic marker and suggest a novel therapeutic approach to overcome therapy resistance in pediatric T-LBL patients.

Nephrology consultation and kidney failure in people with stage 4 chronic kidney disease: a population-based cohort study.

BACKGROUND: Guidelines recommend referral for nephrology consultation for people with severe chronic kidney disease (CKD) to improve care and renal outcomes, yet the advocated benefits of nephrology referral on CKD progression in this patient population are unclear. METHODS: We linked laboratory and administrative data in Alberta, Canada to identify adults with stage 4 CKD between 2002 and 2014 (follow-up end on March 31, 2017). We studied the association between time-varying receipt of outpatient nephrology consultation and kidney failure (the earlier of renal replacement initiation or eGFR < 10 mL/min/1.73 m2 for more than 3 months), accounting for the competing risk of death. RESULTS: Of the 14,382 participants, 41% were ≥ 85 years old, 33% saw a nephrologist as an outpatient, 9% developed kidney failure, and 53% died over a median of 2.6 years. Compared with people who did not see a nephrologist before or at 7 months (median time to consultation), those who did were more likely to develop kidney failure [5-year risk (95% CI) 0.23 (0.21-0.24) vs 0.07 (0.065-0.075)]. With increasing age or higher eGFR, the 5-year risk of kidney failure became progressively smaller, from 0.24 (0.18-0.29) at age < 65 to 0.01 (0.006-0.015) at age ≥ 85 years and from 0.21 (0.18-0.23) at eGFR 15-19 to 0.066 (0.060-0.072) at eGFR 25-29 mL/min/1.73 m2; yet, the hazard ratio of kidney failure (1.6-4.3) increased following nephrology consultation in people who were older or had higher eGFR. CONCLUSIONS: Adults with stage 4 CKD who see a nephrologist are more likely to develop kidney failure than those who don't, especially within lower absolute risk categories. Although selective referral may explain these findings, there is no evidence of an association between nephrology care and reduced risk of kidney failure in people with severe CKD. Studies are needed to assess the benefits of nephrology consultation in people with moderate CKD.

Long-Term outcome of drug-eluting stents compared with bare metal stents in ST-segment elevation myocardial infarction: results of the paclitaxel- or sirolimus-eluting stent versus bare metal stent in Primary Angioplasty (PASEO) Randomized Trial.

BACKGROUND: Drug-eluting stents may offer benefits in terms of repeat revascularization that may be counterbalanced by a potential higher risk of stent thrombosis, especially among ST-segment elevation myocardial infarction (STEMI) patients. No data have been reported so far on the long-term benefits and safety of drug-eluting stents in STEMI. Thus, the aim of the present study was to evaluate the short- and long-term benefits of sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES) compared with bare metal stents (BMS) in patients undergoing primary angioplasty. METHODS AND RESULTS: Consecutive STEMI patients admitted within 12 hours of symptom onset and undergoing primary angioplasty and stent implantation at a tertiary center with 24-hour primary percutaneous coronary intervention capability were randomly assigned to BMS, PES, or SES. All patients received upstream glycoprotein IIb/IIIa inhibitors. The primary end point was target lesion revascularization at the 1-year follow-up. Secondary end points were death and/or reinfarction, in-stent thrombosis, and major adverse cardiac events (combined death and/or reinfarction and/or target lesion revascularization) at long-term follow-up (up to 4 to 6 years). Cumulative incidence of end points was investigated. No patient was lost to follow-up. From October 1, 2003, to December 31, 2005, 270 patients with STEMI were randomized to BMS (n=90), PES (n=90), or SES (n=90). Procedural success was obtained in 93% to 95% of patients. Follow-up data were available for all patients. Compared with BMS (14.4%), both PES (4.4%; hazard ratio, 0.29; 95% confidence interval, 0.095 to 0.89; P=0.023) and SES (3.3%; hazard ratio, 0.21; 95% confidence interval, 0.06 to 0.75; P=0.016) were associated with a significant reduction in target lesion revascularization at the 1-year follow-up (primary study end point). At the long-term follow-up (4.3 years; 25th to 75th percentile, 3.7 to 5 years), no difference was observed in terms of death, reinfarction, and combined death and/or reinfarction, but compared with BMS (22.2%), both PES (6.7%; hazard ratio, 0.27; 95% confidence interval, 0.11 to 0.68; P=0.005) and SES (5.6%; hazard ratio, 0.22; 95% confidence interval, 0.083 to 0.59; P=0.003) were associated with a significant reduction in target lesion revascularization. CONCLUSIONS: This study shows that among STEMI patients undergoing primary angioplasty, both SES and PES are associated with significant benefits in terms of target lesion revascularization at the long-term follow-up compared with BMS with no excess risk of thrombotic complications. Thus, until the results of further large randomized trials with long-term follow-up become available, drug-eluting stents may be considered among STEMI patients undergoing primary angioplasty.

Competing risks and time-dependent covariates.

Time-dependent covariates are frequently encountered in regression analysis for event history data and competing risks. They are often essential predictors, which cannot be substituted by time-fixed covariates. This study briefly recalls the different types of time-dependent covariates, as classified by Kalbfleisch and Prentice [The Statistical Analysis of Failure Time Data, Wiley, New York, 2002] with the intent of clarifying their role and emphasizing the limitations in standard survival models and in the competing risks setting. If random (internal) time-dependent covariates are to be included in the modeling process, then it is still possible to estimate cause-specific hazards but prediction of the cumulative incidences and survival probabilities based on these is no longer feasible. This article aims at providing some possible strategies for dealing with these prediction problems. In a multi-state framework, a first approach uses internal covariates to define additional (intermediate) transient states in the competing risks model. Another approach is to apply the landmark analysis as described by van Houwelingen [Scandinavian Journal of Statistics 2007, 34, 70-85] in order to study cumulative incidences at different subintervals of the entire study period. The final strategy is to extend the competing risks model by considering all the possible combinations between internal covariate levels and cause-specific events as final states. In all of those proposals, it is possible to estimate the changes/differences of the cumulative risks associated with simple internal covariates. An illustrative example based on bone marrow transplant data is presented in order to compare the different methods.

Positive bone marrow biopsy is associated with a decreased disease-free survival in patients with operable breast cancer.

BACKGROUND: Bone marrow (BM) biopsy has been suggested as an independent prognostic factor in patients with breast cancer. METHODS: Patients operated for breast cancer from June 2000 to April 2008 were enrolled in this protocol after signing an informed consent. After primary surgery, BM aspirate from the iliac crest was obtained and 5-10 cc of blood collected. Since 2002 a peripheral blood (PB) sample was also obtained. Both carcinoembryonic antigen (CEA) and Mammaglobin-specific nested reverse-transcription polymerase chain reaction (RT-PCR) were used to examine BM and PB samples. Physicians and patients were blinded to results. RESULTS: Two hundred seventy-three patients underwent BM and/or PB test. The median age of the patients was 63 years (31-80 years), and the median tumor diameter was 1.5 cm (0.1-6 cm). BM aspirates were unsuccessful in nine patients, and RT-PCR was not technically feasible in 18 women, leaving 246 patients available for analysis of results and follow-up. Among them, 110 patients (45%) had either a BM or a PB test positive for CEA or Mammaglobin (Test+). At median follow-up of 60 months, 31 events (deaths or relapse) occurred (13%). Disease-free survival (DFS) was significantly lower in the Test+ group (BP and/or PB) (P<0.001). This effect was independent of nodal status. At 5 years, event-free survival for Node-/Test- patients was 46/49 (94%) and for Node+/Test+ patients was 21/33 (64%), while patients with only one status positive (Node-/Test+ or Node+/Test-) had an intermediate disease-free survival (35/43, 81%) (P=0.005). In a subgroup analysis, RT-PCR results for BM and Mammaglobin retained statistical significance on DFS (P<0.001), while those for PB and CEA did not. CONCLUSIONS: This study confirms that RT-PCR of the BM is an independent prognostic factor for disease-free survival of breast cancer patients, and may improve their staging, allowing better strategies for therapy and follow-up.

Overview of model validation for survival regression model with competing risks using melanoma study data.

The article introduces how to validate regression models in the analysis of competing risks. The prediction accuracy of competing risks regression models can be assessed by discrimination and calibration. The area under receiver operating characteristic curve (AUC) or Concordance-index, and calibration plots have been widely used as measures of discrimination and calibration, respectively. One-time splitting method can be used for randomly splitting original data into training and test datasets. However, this method reduces sample sizes of both training and testing datasets, and the results can be different by different splitting processes. Thus, the cross-validation method is more appealing. For time-to-event data, model validation is performed at each analysis time point. In this article, we review how to perform model validation using the riskRegression package in R, along with plotting a nomogram for competing risks regression models using the regplot() package.

A comparison of confidence/credible interval methods for the area under the ROC curve for continuous diagnostic tests with small sample size.

The receiver operating characteristic (ROC) curve is frequently used as a measure of accuracy of continuous markers in diagnostic tests. The area under the ROC curve (AUC) is arguably the most widely used summary index for the ROC curve. Although the small sample size scenario is common in medical tests, a comprehensive study of small sample size properties of various methods for the construction of the confidence/credible interval (CI) for the AUC has been by and large missing in the literature. In this paper, we describe and compare 29 non-parametric and parametric methods for the construction of the CI for the AUC when the number of available observations is small. The methods considered include not only those that have been widely adopted, but also those that have been less frequently mentioned or, to our knowledge, never applied to the AUC context. To compare different methods, we carried out a simulation study with data generated from binormal models with equal and unequal variances and from exponential models with various parameters and with equal and unequal small sample sizes. We found that the larger the true AUC value and the smaller the sample size, the larger the discrepancy among the results of different approaches. When the model is correctly specified, the parametric approaches tend to outperform the non-parametric ones. Moreover, in the non-parametric domain, we found that a method based on the Mann-Whitney statistic is in general superior to the others. We further elucidate potential issues and provide possible solutions to along with general guidance on the CI construction for the AUC when the sample size is small. Finally, we illustrate the utility of different methods through real life examples.

Recent advances in mathematical modeling and statistical analysis of exocytosis in endocrine cells.

Most endocrine cells secrete hormones as a result of Ca2+-regulated exocytosis, i.e., fusion of the membranes of hormone-containing secretory granules with the cell membrane, which allows the hormone molecules to escape to the extracellular space. As in neurons, electrical activity and cell depolarization open voltage-sensitive Ca2+ channels, and the resulting Ca2+ influx elevate the intracellular Ca2+ concentration, which in turn causes exocytosis. Whereas the main molecular components involved in exocytosis are increasingly well understood, quantitative understanding of the dynamical aspects of exocytosis is still lacking. Due to the nontrivial spatiotemporal Ca2+ dynamics, which depends on the particular pattern of electrical activity as well as Ca2+ channel kinetics, exocytosis is dependent on the spatial arrangement of Ca2+ channels and secretory granules. For example, the creation of local Ca2+ microdomains, where the Ca2+ concentration reaches tens of µM, are believed to be important for triggering exocytosis. Spatiotemporal simulations of buffered Ca2+ diffusion have provided important insight into the interplay between electrical activity, Ca2+ channel kinetics, and the location of granules and Ca2+ channels. By confronting simulations with statistical time-to-event (or survival) regression analysis of single granule exocytosis monitored with TIRF microscopy, a direct connection between location and rate of exocytosis can be obtained at the local, single-granule level. To get insight into whole-cell secretion, simplifications of the full spatiotemporal dynamics have shown to be highly helpful. Here, we provide an overview of recent approaches and results for quantitative analysis of Ca2+ regulated exocytosis of hormone-containing granules.