Robust Small Sample Accurate Inference in Moment Condition Models

Procedures based on the Generalized Method of Moments (GMM) (Hansen, 1982) are basic tools in modern econometrics. In most cases, the theory available for making inference with these procedures is based on first order asymptotic theory. It is well-known that the (first order) asymptotic distribution does not provide accurate p-values and confidence intervals in moderate to small samples. Moreover, in the presence of small deviations from the assumed model, p-values and confidence intervals based on classical GMM procedures can be drastically affected (nonrobustness). Several alternative techniques have been proposed in the literature to improve the accuracy of GMM procedures. These alternatives address either the first order accuracy of the approximations (information and entropy econometrics (IEE)) or the nonrobustness (Robust GMM estimators and tests). In this paper, we propose a new alternative procedure which combines robustness properties and accuracy in small samples. Specifically, we combine IEE techniques as developed in Imbens, Spady, Johnson (1998) to obtain finite sample accuracy with robust methods obtained by bounding the original orthogonality function as proposed in Ronchetti and Trojani (2001). This leads to new robust estimators and tests in moment condition models with excellent finite sample accuracy. Finally, we illustrate the accuracy of the new statistic by means of some simulations for three models on overidentifying moment conditions.Exponential tilting, Generalized method of moments, Information and entropy econometrics, Monte Carlo, Robust tests, Saddlepoint techniques

The prognostic value of tumor mitotic rate in children and adolescents with cutaneous melanoma:A retrospective cohort study

Background: Mitotic rate is a strong predictor of outcome in adult patients with primary cutaneous melanoma, but for children and adolescent patients this is unknown. Objective: We sought to assess the prognostic value of primary tumor mitotic rate in children and adolescents with primary melanoma. Methods: This was a cohort study of 156 patients who were <20 years of age and who had clinically localized cutaneous melanoma. Patients <12 years of age were classified as children and those 12 to 19 years of age as adolescents. Clinicopathologic and outcome data were collected. Recurrence-free and melanoma-specific survival were calculated. Univariable and multivariable analyses were performed using Cox proportional hazard models. Results: Thirteen of 156 patients (8%) were children. The mitotic rate was ≥1/mm2 in 104 patients (67%) and correlated with increasing Breslow thickness. A positive sentinel node was found in 23 of 61 patients (38%) in whom a sentinel lymph node biopsy specimen was obtained. The median follow-up was 61 months. Five-year melanoma-specific and recurrence-free survival rates were 91% and 84%, respectively. Mitotic rate was a stronger predictor of outcome than tumor thickness and was the only factor independently associated with recurrence-free survival. Limitations: This research was conducted at a single institution and the sample size was small. Conclusion: Mitotic rate is an independent predictor of recurrence-free survival in children and adolescents with clinically localized melanoma

Adjuvant radiotherapy after salvage surgery for melanoma recurrence in a node field following a previous lymph node dissection

Background and Objectives: Adjuvant radiotherapy (RT) can be given to melanoma patients following salvage surgery for node field recurrence after a previous regional node dissection, but the value of this treatment strategy is poorly documented. This study evaluated long-term node field control and survival of patients treated in this way in an era before effective adjuvant systemic therapy became available. Methods: Data for 76 patients treated between 1990 and 2011 were extracted from an institutional database. Baseline patient characteristics, treatment details and oncological outcomes were analysed. Results: Adjuvant RT with conventional fractionation (median dose 48 Gy in 20 fractions) was given to 43 patients (57%) and hypofractionated RT (median dose 33 Gy in 6 fractions) to 33 patients (43%). The 5-year node field control rate was 70%, 5-year recurrence-free survival 17%, 5-year melanoma-specific survival 26% and 5-year overall survival 25%. Conclusions: Salvage surgery with adjuvant RT achieved node field control in 70% of melanoma patients with node field recurrence following a prior node dissection. However, disease progression at distant sites was common and survival outcomes were poor. Prospective data will be required to assess outcomes for contemporary combinations of surgery, adjuvant RT and systemic therapy.</p

Efficacy and toxicity of adjuvant radiotherapy in recurrent melanoma after adjuvant immunotherapy

BackgroundIn patients with stage III melanoma, despite surgical resection and adjuvant systemic therapy, locoregional recurrences still occur. The randomized, phase III Trans-Tasman Radiation Oncology Group (TROG) 02.01 trial demonstrated that adjuvant radiotherapy (RT) after complete lymphadenectomy (CLND) halves the incidence of melanoma recurrence within local nodal basins without improving overall survival or quality of life. However, the study was conducted prior to the current era of adjuvant systemic therapies and when CLND was the standard approach for microscopic nodal disease. As such, there is currently no data on the role of adjuvant RT in patients with melanoma who recur during or after adjuvant immunotherapy, including those that may or may not have undergone prior CLND. In this study, we aimed to answer this question.MethodsPatients with resected stage III melanoma who received adjuvant anti-programmed cell death protein-1 (PD-1) (±ipilimumab) immunotherapy with a subsequent locoregional (lymph node and/or in-transit metastases) recurrence were retrospectively identified. Multivariable logistic and Cox regression analyses were conducted. Primary outcome was rate of subsequent locoregional recurrence; secondary outcomes were locoregional recurrence-free survival (lr-RFS2) and overall RFS (RFS2) to second recurrence.ResultsIn total, 71 patients were identified: 42 (59%) men, 30 (42%) BRAF V600E mutant, 43 (61%) stage IIIC at diagnosis. Median time to first recurrence was 7 months (1–44), 24 (34%) received adjuvant RT and 47 (66%) did not. Thirty-three patients (46%) developed a second recurrence at a median of 5 months (1–22). The rate of locoregional relapse at second recurrence was lower in those who received adjuvant RT (8%, 2/24) compared with those who did not (36%, 17/47, p=0.01). Adjuvant RT at first recurrence was associated with an improved lr-RFS2 (HR 0.16, p=0.015), with a trend towards an improved RFS2 (HR 0.54, p=0.072) and no effect on risk of distant recurrence or overall survival.ConclusionThis is the first study to investigate the role of adjuvant RT in patients with melanoma with locoregional disease recurrence during or after adjuvant anti-PD-1-based immunotherapy. Adjuvant RT was associated with improved lr-RFS2, but not risk of distant recurrence, demonstrating a likely benefit in locoregional disease control in the modern era. Further prospective studies are required to validate these results

The Impact of Surveillance Imaging Frequency on the Detection of Distant Disease for Patients with Resected Stage III Melanoma

Background It is not known whether there is a survival benefit associated with more frequent surveillance imaging in patients with resected American Joint Committee on Cancer stage III melanoma. Objective The aim of this study was to investigate distant disease-free survival (DDFS), melanoma-specific survival (MSS), post distant recurrence MSS (dMSS), and overall survival for patients with resected stage III melanoma undergoing regular computed tomography (CT) or positron emission tomography (PET)/CT surveillance imaging at different intervals. Patients and Methods A closely followed longitudinal cohort of patients with resected stage IIIA–D disease treated at a tertiary referral center underwent 3- to 4-monthly, 6-monthly, or 12-monthly surveillance imaging between 2000 and 2017. Survival outcomes were estimated using the Kaplan–Meier method, and log-rank tests assessed the significance of survival differences between imaging frequency groups. Results Of 473 patients (IIIA, 19%; IIIB, 31%; IIIC, 49%; IIID, 1%) 30% underwent 3- to 4-monthly imaging, 10% underwent 6-monthly imaging, and 60% underwent 12-monthly imaging. After a median follow-up of 6.2 years, distant recurrence was recorded in 252 patients (53%), with 40% detected by surveillance CT or PET/CT, 43% detected clinically, and 17% with another imaging modality. Median DDFS was 5.1 years (95% confidence interval 3.9–6.6). Among 139 IIIC patients who developed distant disease, the median dMSS was 4.4 months shorter in those who underwent 3- to 4-monthly imaging than those who underwent 12-monthly imaging. Conclusion Selecting patients at higher risk of distant recurrence for more frequent surveillance imaging yields a higher proportion of imaging-detected distant recurrences but is not associated with improved survival. A randomized comparison of low versus high frequency imaging is needed

Whole brain radiotherapy (WBRT) after local treatment of brain metastases in melanoma patients: Statistical Analysis Plan

Background: The WBRTMel trial is a multinational, open-label, phase III randomised controlled trial comparing whole brain radiotherapy (WBRT) to observation following local treatment of one to three melanoma brain metastases with surgery and/or stereotactic irradiation. The primary trial endpoint was to determine the effect of adding WBRT to local treatment on distant intracranial control, and the secondary endpoints were neurocognitive function, quality of life (QoL), performance status, overall survival, death from intracranial causes, death from melanoma and cost-effectiveness. Objective: The objective of this update is to outline and publish the pre-determined statistical analysis plan (SAP) before the database lock and the start of analysis. Methods: The SAP describes basic analysis principles, methods for dealing with a range of commonly encountered data analysis issues and the specific statistical procedures for analysing efficacy and safety outcomes. The SAP was approved after closure of recruitment and before completion of patient follow-up. It outlines the planned primary analyses and a range of subgroup and sensitivity analyses regarding the clinical and QoL outcomes. Health economic outcomes are not included in this plan but will be analysed separately. The SAP will be adhered to for the final data analysis of this trial to avoid analysis bias arising from knowledge of the data. Results: The resulting SAP is consistent with best practice and will allow open and transparent reporting. Conclusion: We have developed a SAP for the WBRTMel trial which will be followed to ensure high-quality standards of internal validity to minimise analysis bias

An integrated general practice and pharmacy-based intervention to promote the use of appropriate preventive medications among individuals at high cardiovascular disease risk: protocol for a cluster randomized controlled trial

Background: Cardiovascular diseases (CVD) are responsible for significant morbidity, premature mortality, and economic burden. Despite established evidence that supports the use of preventive medications among patients at high CVD risk, treatment gaps remain. Building on prior evidence and a theoretical framework, a complex intervention has been designed to address these gaps among high-risk, under-treated patients in the Australian primary care setting. This intervention comprises a general practice quality improvement tool incorporating clinical decision support and audit/feedback capabilities; availability of a range of CVD polypills (fixed-dose combinations of two blood pressure lowering agents, a statin ± aspirin) for prescription when appropriate; and access to a pharmacy-based program to support long-term medication adherence and lifestyle modification. Methods: Following a systematic development process, the intervention will be evaluated in a pragmatic cluster randomized controlled trial including 70 general practices for a median period of 18 months. The 35 general practices in the intervention group will work with a nominated partner pharmacy, whereas those in the control group will provide usual care without access to the intervention tools. The primary outcome is the proportion of patients at high CVD risk who were inadequately treated at baseline who achieve target blood pressure (BP) and low-density lipoprotein cholesterol (LDL-C) levels at the study end. The outcomes will be analyzed using data from electronic medical records, utilizing a validated extraction tool. Detailed process and economic evaluations will also be performed. Discussion: The study intends to establish evidence about an intervention that combines technological innovation with team collaboration between patients, pharmacists, and general practitioners (GPs) for CVD prevention. Trial registration: Australian New Zealand Clinical Trials Registry ACTRN1261600023342

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century