Conditional survival to assess prognosis in patients with chronic lymphocytic leukemia.

Biomarkers in chronic lymphocytic leukemia (CLL) allow assessment of prognosis. However, the validity of current prognostic biomarkers based on a single assessment point remains unclear for patients who have survived one or more years. Conditional survival (CS) studies that address how prognosis may change over time, especially in prognostic subgroups, are still rare. We performed CS analyses to estimate 5-year survival in 1-year increments, stratified by baseline disease characteristics and known risk factors in two community-based cohorts of CLL patients (Freiburg University Hospital (n = 316) and Augsburg University Hospital (n = 564)) diagnosed between 1984 and 2021. We demonstrate that 5-year CS probability is stable (app. 75%) for the entire CLL patient cohort over 10 years. While age, sex, and stage have no significant impact on CS, patients with high-risk disease features such as non-mutated IGHV, deletion 17p, and high-risk CLL-IPI have a significantly worse prognosis at diagnosis, and 5-year CS steadily decreases with each additional year survived. Our results confirm that CLL patients have a stable survival probability with excess mortality and that the prognosis of high-risk CLL patients declines over time. We infer that CS-based prognostic information is relevant for disease management and counseling of CLL patients.

How do SGLT2 inhibitors protect the kidney? A mediation analysis of the EMPA-REG OUTCOME trial.

INTRODUCTION: Mechanisms underlying kidney benefits with sodium-glucose cotransporter-2 (SGLT2) inhibition in heart failure and/or type 2 diabetes (T2D) with established cardiovascular disease are currently unclear. METHODS: We evaluated post hoc the factors mediating the effect of empagliflozin on a composite kidney outcome (first sustained estimate glomerular filtration rate ≥40% reduction from baseline, initiation of renal replacement therapy, or death due to kidney disease) in EMPA-REG OUTCOME. Variables, calculated as change from baseline or updated mean, were evaluated as time-dependent covariates and using a landmark approach (at Week 12) in Cox regression analyses. In multivariable analyses, variables with the greatest mediating effect were added using a step-up procedure. RESULTS: In univariable time-dependent updated mean covariate analyses, the strongest mediator was hematocrit (99.5% mediation). Hemoglobin, uric acid, and urine albumin-to-creatinine ratio mediated 79.4%, 33.2%, and 31.0%, respectively. Multivariable analyses were not performed due to the very strong mediation effect of hematocrit. In univariable Week 12 landmark change from baseline analyses, the strongest mediators included hematocrit (40.7%), glycated hemoglobin (28.3%), systolic blood pressure (16.8%), and free fatty acids (16.5%), which yielded a combined mediation of 78.9% in multivariable analysis. CONCLUSIONS: Changes in hematocrit and hemoglobin were the strongest mediators of empagliflozin's kidney benefits in EMPA-REG OUTCOME participants with T2D and cardiovascular disease.

Men with erectile dysfunction (ED) should be screened for cardiovascular risk factors - Cost-benefit considerations in Swiss men.

Background: Current evidence indicates that erectile dysfunction (ED) is an independent risk factor for future cardiovascular events. This study aimed to estimate the cost-effectiveness of screening and subsequent preventive treatment for cardiovascular risk factors among men newly diagnosed with ED from the Swiss healthcare system perspective. Methods: Based on known data on ED and cardiovascular disease (CVD) prevalence and incidence costs and effects of a screening intervention for cardiovascular risk including corresponding cardiovascular prevention in men with ED were calculated for the Swiss population over a period of 10 years. Results: Screening and cardiovascular prevention over a period of 10 years in Swiss men with ED of all seriousness degrees, moderate and severe ED only, or severe ED only can probably avoid 41,564, 35,627, or 21,206 acute CVD events, respectively. Number needed to screen (NNS) to prevent one acute CVD event is 30, 23, and 10, respectively. Costs for the screening intervention are expected to be covered at the seventh, the fifth, and the first year, respectively. Conclusion: Screening and intervention for cardiovascular risk factors in men suffering from ED is a cost-effective tool not only to strengthen prevention and early detection of cardiovascular diseases but also to avoid future cardiovascular events.

Speaking in gestures: Left dorsal and ventral frontotemporal brain systems underlie communication in conducting.

Conducting constitutes a well-structured system of signs anticipating information concerning the rhythm and dynamic of a musical piece. Conductors communicate the musical tempo to the orchestra, unifying the individual instrumental voices to form an expressive musical Gestalt. In a functional magnetic resonance imaging (fMRI) experiment, 12 professional conductors and 16 instrumentalists conducted real-time novel pieces with diverse complexity in orchestration and rhythm. For control, participants either listened to the stimuli or performed beat patterns, setting the time of a metronome or complex rhythms played by a drum. Activation of the left superior temporal gyrus (STG), supplementary and premotor cortex and Broca's pars opercularis (F3op) was shared in both musician groups and separated conducting from the other conditions. Compared to instrumentalists, conductors activated Broca's pars triangularis (F3tri) and the STG, which differentiated conducting from time beating and reflected the increase in complexity during conducting. In comparison to conductors, instrumentalists activated F3op and F3tri when distinguishing complex rhythm processing from simple rhythm processing. Fibre selection from a normative human connectome database, constructed using a global tractography approach, showed that the F3op and STG are connected via the arcuate fasciculus, whereas the F3tri and STG are connected via the extreme capsule. Like language, the anatomical framework characterising conducting gestures is located in the left dorsal system centred on F3op. This system reflected the sensorimotor mapping for structuring gestures to musical tempo. The ventral system centred on F3Tri may reflect the art of conductors to set this musical tempo to the individual orchestra's voices in a global, holistic way.

Long-Term Outcomes of Drug-Eluting Stent Implantation for Patients With Atherosclerotic Erectile Dysfunction not Responding to PDE-5-Inhibitors.

PURPOSE: Endovascular therapy of erection-related arteries was shown to be a promising treatment option for patients with severe erectile dysfunction. Purpose of this study was to assess the longer-term safety and clinical success rate of endovascular revascularization of erection-related arteries with the Angiolite BTK stent in patients with arteriogenic erectile dysfunction. MATERIALS AND METHODS: A total of 147 consecutive men (63.5±9.3 years) with erectile dysfunction due to 345 atherosclerotic lesions underwent endovascular revascularization. Patients received an International Index of Erectile Function (IIEF)-15 questionnaire at 30.3±7.2 months (follow-up [FU] period no less than 18 months) after stenting. An improvement by 4 points in the erectile function domain consisting of 6 questions (IIEF-6) was defined as minimal clinically important difference (MCID). RESULTS: Technical success was achieved in 99% of lesions. One major adverse event occurred after endovascular revascularization. Sixty-eight (46%) patients completed their latest FU at least 18 months following the last intervention. Minimal clinically important difference was achieved in 54% (37/68) of patients. CONCLUSIONS: In patients with arteriogenic erectile dysfunction not responding to phosphodiesterase-5-inhibitors (PDE-5-Is), endovascular therapy with a novel thin-strut sirolimus-eluting stent is a safe and effective treatment option during short- and longer-term FU. CLINICAL IMPACT: Patients with severe erectile dysfunction profit greatly from endovascular therapy of erection-related arteries. Stable clinical outcomes are seen beyond a 1-year timeframe. It is proven that, the drug-eluting stent therapy for atherosclerotic ED in patients who have not responded to PDE-5-I therapy is safe and effective during longer-term follow-up.

Multidisciplinary tumor boards and their analyses: the yin and yang of outcome measures.

BACKGROUND: The standard to ensure utmost cancer treatment is a prerequisite in national cancer plans for comprehensive cancer centers (CCCs) and ensured through multidisciplinary tumor boards (MTBs). Despite these being compulsory for CCCs, various analyses on MTBs have been performed, since MTBs are resource-intensive. Outcome measures in these prior analyses had been survival (OS), MTB-adherence and -satisfaction, inclusion of patients into clinical trials and better cancer care. MAIN BODY: A publication from Freytag et al. performed an analysis in multiple tumor entities and assessed the effect of number of MTBs. By matched-pair analysis, they compared response and OS of patients, whose cases were discussed in MTBs vs. those that were not. The analysis included 454 patients and 66 different tumor types. Only patients with > 3 MTBs showed a significantly better OS than patients with no MTB meeting. Response to treatment, relapse free survival and time to progression were not found to be better, nor was there any difference for a specific tumor entity with vs. without MTB discussions. An in-depth discussion of these results, with respect to the literature (PubMed search: "MTBs AND cancer") and within the author group, including statisticians specialized in data analysis of cancer patients and questions addressed in MTBs, was performed to interpret these findings. We conclude that the results by Freytag et al. are deceiving due to an "immortal time bias" that requires more careful data interpretation. CONCLUSIONS: The result of Freytag et al. of a seemingly positive impact of higher number of MTBs needs to be interpreted cautiously: their presumed better OS in patients with > 3 MTB discussions is misleading, due to an immortal time bias. Here patients need to survive long enough to be discussed more often. Therefore, these results should not lead to the conclusion that more MTBs will "automatically" increase cancer patients' OS, rather than that the insightful discussion, at best in MTBs and with statisticians, will generate meaningful advice, that is important for cancer patients.

Endovascular Therapy for Arteriogenic Erectile Dysfunction With a Novel Sirolimus-Eluting Stent.

BACKGROUND: Arteriogenic erectile dysfunction is a common disease oftentimes not satisfactory treatable with medical therapy. AIM: To assess the safety and clinical success rate of endovascular revascularization of erection-related arteries with the angiolite BTK stent in patients with arteriogenic erectile dysfunction. METHODS: A total of 100 consecutive men (61.8 ± 10 years) with atherosclerotic lesions in erection-related arteries agreed to participate and were included into a single-center all-comers registry. Endovascular therapy with angiolite BTK drug-eluting stents was performed on a total of 211 lesions. Patients received a baseline International Index of Erectile Function (IIEF)-15 questionnaire at first presentation and 3 and 12 months after stenting. An improvement by 4 points in the erectile function domain consisting of 6 questions (IIEF-6) was defined as minimal clinically important difference. A total of 24 patients with 52 stented arterial lesions underwent angiographic follow-up of the initially treated arterial side during secondary revascularization of the contralateral side (angiographic sub-study). OUTCOME: Clinical improvement of erections in 100 patients undergoing endovascular revascularization of erection-related arteries. RESULTS: No major adverse events occurred during endovascular revascularization or within 30 days thereafter. Technical success was achieved in all lesions and procedural success in all patients. At 1 year, 55 of 97 patients (56.7%) improved by at least 4 points in IIEF-6 score and thus achieved a clinically relevant improvement of erectile function.In the angiographic sub-study, arterial patency and binary restenosis were observed in 46 of 52 (88.5%) and in 8 of 52 (15.4%), respectively, after a mean follow-up of 9.6 ± 5.8 months. CLINICAL IMPLICATIONS: In patients with arteriogenic erectile dysfunction, endovascular therapy with a novel thin-strut sirolimus eluting stent is a safe and feasible treatment option. STRENGTHS & LIMITATIONS: This real-world arterial revascularization registry included patients with a multitude of risk factors for ED, thereby representing the heterogeneity in patients in the clinical practice, which is one of its strengths but also one of its weaknesses. Another strength was the focus being laid on analyzing outcomes of patients with arteriogenic ED using only a single endovascular device. Further studies are warranted to better define subgroups of patients with impaired clinical outcomes. CONCLUSION: Within the present all-comers registry, endovascular therapy of erectile dysfunction with the angiolite BTK stent was shown to be a safe and feasible treatment option resulting in clinical improvement rates comparable to earlier clinical trials although also showing that further research is warranted to define patient subgroups with particular benefits of endovascular therapy. Schönhofen J, Räber L, Knöchel J, et al. Endovascular Therapy for Arteriogenic Erectile Dysfunction With a Novel Sirolimus-Eluting Stent. J Sex Med 2021;18:315-326.

Quantifying and communicating the burden of COVID-19.

BACKGROUND: An essential aspect of preventing further COVID-19 outbreaks and to learn for future pandemics is the evaluation of different political strategies, which aim at reducing transmission of and mortality due to COVID-19. One important aspect in this context is the comparison of attributable mortality. METHODS: We give a comprehensive overview of six epidemiological measures that are used to quantify COVID-19 attributable mortality (p-score, standardized mortality ratio, absolute number of excess deaths, per capita rate, z-score and the population attributable fraction). RESULTS: By defining the six measures based on observed and expected deaths, we explain their relationship. Moreover, three publicly available data examples serve to illustrate the interpretational strengths and weaknesses of the various measures. Finally, we give recommendation which measures are suitable for an evaluation of public health strategies against COVID-19. The R code to reproduce the results is available as online supplementary material. CONCLUSION: The number of excess deaths should be always reported together with the population attributable fraction, the p-score or the standardized mortality ratio instead of a per capita rate. For a complete picture of COVID-19 attributable mortality, quantifying and communicating its relative burden also to a lay audience is of major importance.

Investigator initiated trials versus industry sponsored trials - translation of randomized controlled trials into clinical practice (IMPACT).

BACKGROUND: Healthcare decisions are ideally based on clinical trial results, published in study registries, as journal articles or summarized in secondary research articles. In this research project, we investigated the impact of academically and commercially sponsored clinical trials on medical practice by measuring the proportion of trials published and cited by systematic reviews and clinical guidelines. METHODS: We examined 691 multicenter, randomized controlled trials that started in 2005 or later and were completed by the end of 2016. To determine whether sponsorship/funding and place of conduct influence a trial's impact, we created four sub-cohorts of investigator initiated trials (IITs) and industry sponsored trials (ISTs): 120 IITs and 171 ISTs with German contribution compared to 200 IITs and 200 ISTs without German contribution. We balanced the groups for study phase and place of conduct. German IITs were funded by the German Research Foundation (DFG), the Federal Ministry of Education and Research (BMBF), or by another non-commercial research organization. All other trials were drawn from the German Clinical Trials Register or ClinicalTrials.gov. We investigated, to what extent study characteristics were associated with publication and impact using multivariable logistic regressions. RESULTS: For 80% of the 691 trials, results were published as result articles in a medical journal and/or study registry, 52% were cited by a systematic review, and 26% reached impact in a clinical guideline. Drug trials and larger trials were associated with a higher probability to be published and to have an impact than non-drug trials and smaller trials. Results of IITs were more often published as a journal article while results of ISTs were more often published in study registries. International ISTs less often gained impact by inclusion in systematic reviews or guidelines than IITs. CONCLUSION: An encouraging high proportion of the clinical trials were published, and a considerable proportion gained impact on clinical practice. However, there is still room for improvement. For publishing study results, study registries have become an alternative or complement to journal articles, especially for ISTs. IITs funded by governmental bodies in Germany reached an impact that is comparable to international IITs and ISTs.

Frequency and anatomic distribution of arterial obstructions in patients with vasculogenic erectile dysfunction not responding to intracavernous prostaglandin.

Background: The extent of arterial disease in patients with erectile dysfunction (ED) non-responsive to intracavernosal injection of Alprostadil is of importance for therapeutic options. However, published evidence, in particular angiographically validated is scarce. Here we investigated arterial lesion patterns in this specific patient cohort by selective angiography. Patients and methods: A cohort of 239 patients received a clinical and duplex-sonographic workup for ED of suspected vascular origin. Duplex ultrasound of the cavernosal arteries was performed after intracavernosal injection of 10 µg Alprostadil. Consequently, standardized workup included grading of the erectile and determination of peak systolic velocity (PSV) and end-diastolic velocity (EDV) in both cavernosal arteries. PSV-values below 30 cm/sec indicated reduced arterial flow, whereas EDV-values above 15 cm/sec indicated a venous leak of the pudendal veins. All patients with suspected arterial ED based on duplex sonography underwent contrast-enhanced computed tomography. Endovascular therapy was carried out in ED patients not responsive or with significant side effects to PDE-5-inhibitors or Alprostadil by selective angiographic depiction of erection-related arteries. Results: 54 patients with a mean age of 61.2 (±9.8) years underwent angioplasty of erectionr elated arteries. Out of these 48/54 (89%) patients presented with an erection considered insufficient for penetration (E0-E3) subsequent to intracavernous application of 10 µg Alprostadil. 14/48 (29%) patients had bilateral arterial obstructions and 34/48 (71%) had unilateral disease. Commonly affected was the internal pudendal artery (n = 31, 65%), followed closely by the common penile artery (n = 30, 64%). The least affected arteries were the dorsal penile (n = 6, 13%), hypogastric (n = 4, 8%), common iliac (n = 4, 8%), cavernosal (n = 4, 8%), and inferior gluteal (n = 1, 2%) arteries. Conclusions: Arterial obstructions amenable to endovascular revascularization are frequent in patients non-responsive to intracavernosal prostaglandin administration. Therapeutic strategies in ED patients non-responsive to conservative measures should therefore consider endovascular treatment opportunities.

A shared frailty model for multivariate longitudinal data on adverse event of radiation therapy.

Oral mucositis is an inflammatory adverse event when treating head and neck cancer patients with radiation therapy (RT). The severity of its occurrence is believed to mainly depend on its site and the distribution of a cumulative radiation dose in the mouth area. The motivating study investigating differences in radiosensitivities (mucositis progression) at distinct sites where the severity of mucositis is assessed regularly at eight distinct sites on an ordinal scale results in multivariate longitudinal data and thus poses certain challenges. To deal with the multivariate longitudinal data in this particular setting, we take a time-to-event approach focusing on the first occurrence of severe mucositis at the distinct sites using the fact that the site-specific cumulative radiation dose thought to be the main driver of oral mucositis develops over time. Thereby, we may address multivariate longitudinal processes in a simpler and more compact fashion. In this article, to find out differences in mucositis progression at eight distinct sites we propose a shared frailty model for multivariate parallel processes within individuals. The shared frailty model directly incorporating 'process indicators' as covariates turns out to adequately explain the differences in the parallel processes (here, mucositis progressions at distinct sites) while taking individual effects into account. The parallel result with the one from the previous analysis based on the same data but conducted with an alternative statistical methodology shows adequacy of the proposed approach.

Doug Altman: Driving critical appraisal and improvements in the quality of methodological and medical research.

Doug Altman was a visionary leader and one of the most influential medical statisticians of the last 40 years. Based on a presentation in the "Invited session in memory of Doug Altman" at the 40th Annual Conference of the International Society for Clinical Biostatistics (ISCB) in Leuven, Belgium and our long-standing collaborations with Doug, we discuss his contributions to regression modeling, reporting, prognosis research, as well as some more general issues while acknowledging that we cannot cover the whole spectrum of Doug's considerable methodological output. His statement "To maximize the benefit to society, you need to not just do research but do it well" should be a driver for all researchers. To improve current and future research, we aim to summarize Doug's messages for these three topics.

Relapse- and Immunosuppression-Free Survival after Hematopoietic Stem Cell Transplantation: How Can We Assess Treatment Success for Complex Time-to-Event Endpoints?

In most clinical oncology trials, time-to-first-event analyses are used for efficacy assessment, which often do not capture the entire disease process. Instead, the focus may be on more complex time-to-event endpoints, such as the course of disease after the first event or endpoints occurring after randomization. We propose "relapse- and immunosuppression-free survival" (RIFS) as an innovative and clinically relevant outcome measure for assessing treatment success after hematopoietic stem cell transplant (SCT). To capture the time-dynamic relationship of multiple episodes of immunosuppressive therapy during follow-up, relapse, and nonrelapse mortality, a multistate model was developed. The statistical complexity is that the probability of RIFS is nonmonotonic over time; thus, standard time-to-first-event methodology is inappropriate for formal treatment comparisons. Instead, a generalization of the Kaplan-Meier method was used for probability estimation, and simulation-based resampling was suggested as a strategy for statistical inference. We reanalyzed data from a recently published phase III trial in 201 leukemia patients after SCT. The study evaluated long-term treatment success of standard graft-versus-host disease prophylaxis plus a pretransplant antihuman T-lymphocyte immunoglobulin compared with standard prophylaxis alone. Results suggested that treatment increased the long-term probability of RIFS by approximately 30% during the entire follow-up period, which complements the original findings. This article highlights the importance of complex endpoints in oncology, which provide deeper insight into the treatment and disease process over time. Multistate models combined with resampling are highlighted as a promising tool to evaluate treatment success beyond standard endpoints. An example code is provided in the Supplementary Materials.

Risk of disease recurrence and survival in patients with multiple myeloma: A German Study Group analysis using a conditional survival approach with long-term follow-up of 815 patients.

BACKGROUND: Unlike the traditional method of overall survival prediction in patients with cancer, conditional survival predicts the survival of patients dynamically throughout the course of disease, identifying how a prognosis evolves over time. METHODS: The authors assessed 815 consecutive patients with multiple myeloma through the German Study Group on Multiple Myeloma (Deutsche Studiengruppe Multiples Myelom; DSMM) incentive. Over 10 variables, including patient-specific and multiple myeloma-specific parameters, were analyzed at the time of initial diagnosis and repeatedly during follow-up. The probability of survival for another 5 years was calculated according to disease-related and host-related risks. Multivariate Cox models were used to determine baseline and updated prognostic factors for survival. RESULTS: The median follow-up and overall survival were 10.3 years and 5.1 years, respectively. When comparing 5-year conditional survival probabilities from the data derived at the time of initial diagnosis with those updated over time, substantially differing prognoses were observed when follow-up data were used. Multivariate Cox regression models for cohorts surviving 0 to 5 years demonstrated hazard ratios (HRs) for patients aged <60 years, 60 to 69 years, and >70 years of 1, 1.68, and 3.17, respectively. These HRs for age were found to decline for patients surviving 5 years, as well as for those with advanced stages of disease (II/III) and unfavorable cytogenetics, whereas progressive disease remained an important factor in patients surviving 1 year, 3 years, and 5 years, with HRs of 1.85, 2.11, and 2.14, respectively. CONCLUSIONS: To the authors' knowledge, the current study is the first analysis of conditional survival in patients with multiple myeloma using both baseline and follow-up risk parameters, demonstrating that regular risk assessment throughout the course of disease and complete follow-up provide a more reliable conditional survival estimation than baseline assessment alone.

Higher number of multidisciplinary tumor board meetings per case leads to improved clinical outcome.

BACKGROUND: This analysis aims at evaluating the impact of multidisciplinary tumor boards on clinical outcome of multiple tumor entities, the effect of the specific number of multidisciplinary tumor boards and potential differences between the tumor entities. METHODS: By a matched-pair analysis we compared the response to treatment, overall survival, relapse or disease free survival and progression free survival of patients whose cases were discussed in a tumor board meeting with patients whose cases were not. It was performed with patients registered in the cancer registry of the University of Bonn and diagnosed between 2010 and 2016. After the matching process with a pool of 7262 patients a total of 454 patients with 66 different tumor types were included in this study. RESULTS: First, patients with three or more multidisciplinary tumor board meetings in their history show a significantly better overall survival than patients with no tumor board meeting. Second, response to treatment, relapse free survival and time to progression were not found to be significantly different. Third, there was no significant difference for a specific tumor entity. CONCLUSION: This study revealed a positive impact of a higher number of multidisciplinary tumor boards on the clinical outcome. Also, our analysis hints towards a positive effect of multidisciplinary tumor boards on overall survival.

Recovery of original individual person data (IPD) inferences from empirical IPD summaries only: Applications to distributed computing under disclosure constraints.

There are many settings where individual person data (IPD) are not available, due to privacy or technical reasons, and one must work with IPD proxies, such as summary statistics, to approximate original IPD inferences, that is, the results of statistical analyses that would ideally have been performed on individual-level data. For instance, in a distributed computing setting, as implemented in the DataSHIELD software framework, different centers can only share IPD proxies to obtain pooled IPD inferences. Such privacy requirements limit the scope of statistical investigation. For example, it can be challenging to perform between-center random-effect regression models. To increase modeling freedom we propose a method that only uses simple nondisclosive summaries of the original IPD as input, such as empirical marginal moments and correlation matrices, and generates artificial data compatible with those summary features. Specifically, data are generated from a Gaussian copula with marginal and joint components specified by the above summaries. The goal is to reproduce original IPD features in the artificial data, such that original IPD inferences are recovered from the artificial data. In an application example, and through simulations, we show that we can recover estimates of a multivariable IPD random-effect logistic regression, from artificial data generated via the Gaussian copula using the above IPD summaries, suggesting the proposed approach provides a generally applicable strategy for distributed computing settings with data protection constraints.

Comparison of complex modeling strategies for prediction of a binary outcome based on a few, highly correlated predictors.

Motivated by a clinical prediction problem, a simulation study was performed to compare different approaches for building risk prediction models. Robust prediction models for hospital survival in patients with acute heart failure were to be derived from three highly correlated blood parameters measured up to four times, with predictive ability having explicit priority over interpretability. Methods that relied only on the original predictors were compared with methods using an expanded predictor space including transformations and interactions. Predictors were simulated as transformations and combinations of multivariate normal variables which were fitted to the partly skewed and bimodally distributed original data in such a way that the simulated data mimicked the original covariate structure. Different penalized versions of logistic regression as well as random forests and generalized additive models were investigated using classical logistic regression as a benchmark. Their performance was assessed based on measures of predictive accuracy, model discrimination, and model calibration. Three different scenarios using different subsets of the original data with different numbers of observations and events per variable were investigated. In the investigated setting, where a risk prediction model should be based on a small set of highly correlated and interconnected predictors, Elastic Net and also Ridge logistic regression showed good performance compared to their competitors, while other methods did not lead to substantial improvements or even performed worse than standard logistic regression. Our work demonstrates how simulation studies that mimic relevant features of a specific data set can support the choice of a good modeling strategy.

On the relation between the cause-specific hazard and the subdistribution rate for competing risks data: The Fine-Gray model revisited.

The Fine-Gray proportional subdistribution hazards model has been puzzling many people since its introduction. The main reason for the uneasy feeling is that the approach considers individuals still at risk for an event of cause 1 after they fell victim to the competing risk of cause 2. The subdistribution hazard and the extended risk sets, where subjects who failed of the competing risk remain in the risk set, are generally perceived as unnatural . One could say it is somewhat of a riddle why the Fine-Gray approach yields valid inference. To take away these uneasy feelings, we explore the link between the Fine-Gray and cause-specific approaches in more detail. We introduce the reduction factor as representing the proportion of subjects in the Fine-Gray risk set that has not yet experienced a competing event. In the presence of covariates, the dependence of the reduction factor on a covariate gives information on how the effect of the covariate on the cause-specific hazard and the subdistribution hazard relate. We discuss estimation and modeling of the reduction factor, and show how they can be used in various ways to estimate cumulative incidences, given the covariates. Methods are illustrated on data of the European Society for Blood and Marrow Transplantation.

Dynamic prediction: A challenge for biostatisticians, but greatly needed by patients, physicians and the public.

Prognosis is usually expressed in terms of the probability that a patient will or will not have experienced an event of interest t years after diagnosis of a disease. This quantity, however, is of little informative value for a patient who is still event-free after a number of years. Such a patient would be much more interested in the conditional probability of being event-free in the upcoming t years, given that he/she did not experience the event in the s years after diagnosis, called "conditional survival." It is the simplest form of a dynamic prediction and can be dealt with using straightforward extensions of standard time-to-event analyses in clinical cohort studies. For a healthy individual, a related problem with further complications is the so-called "age-conditional probability of developing cancer" in the next t years. Here, the competing risk of dying from other diseases has to be taken into account. For both situations, the hazard function provides the central dynamic concept, which can be further extended in a natural way to build dynamic prediction models that incorporate both baseline and time-dependent characteristics. Such models are able to exploit the most current information accumulating over time in order to accurately predict the further course or development of a disease. In this article, the biostatistical challenges as well as the relevance and importance of dynamic prediction are illustrated using studies of multiple myeloma, a hematologic malignancy with a formerly rather poor prognosis which has improved over the last few years.

The population-attributable fraction for time-dependent exposures using dynamic prediction and landmarking.

The public health impact of a harmful exposure can be quantified by the population-attributable fraction (PAF). The PAF describes the attributable risk due to an exposure and is often interpreted as the proportion of preventable cases if the exposure was extinct. Difficulties in the definition and interpretation of the PAF arise when the exposure of interest depends on time. Then, the definition of exposed and unexposed individuals is not straightforward. We propose dynamic prediction and landmarking to define and estimate a PAF in this data situation. Two estimands are discussed which are based on two hypothetical interventions that could prevent the exposure in different ways. Considering the first estimand, at each landmark the estimation problem is reduced to a time-independent setting. Then, estimation is simply performed by using a generalized-linear model accounting for the current exposure state and further (time-varying) covariates. The second estimand is based on counterfactual outcomes, estimation can be performed using pseudo-values or inverse-probability weights. The approach is explored in a simulation study and applied on two data examples. First, we study a large French database of intensive care unit patients to estimate the population-benefit of a pathogen-specific intervention that could prevent ventilator-associated pneumonia caused by the pathogen Pseudomonas aeruginosa. Moreover, we quantify the population-attributable burden of locoregional and distant recurrence in breast cancer patients.