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The need to model a cure fraction, the proportion of a cohort not susceptible to the event of interest, arises in a variety of contexts including tumor relapse in oncology. Existing methodology assumes that follow‐up is long enough for all uncured subjects to have experienced the event of interest at the time of analysis, and researchers have demonstrated that fitting cure models without sufficient follow‐up leads to bias. Few statistical methods exist to evaluate sufficient follow‐up, and they can exhibit poor performance and lead users to falsely conclude sufficient follow‐up, leading to bias, or to falsely claim insufficient follow‐up, possibly leading to additional, costly data collection. We propose a new quantitative statistic (RECeUS) to evaluate whether cure models may be appropriate to apply to censored data. Specifically, we propose that the estimated proportion of censored uncured subjects in a study can be used to evaluate cure model appropriateness. We evaluated the performance of RECeUS against existing methods via simulation and with two data examples, and we observe that RECeUS displays superior performance. In simulated and real‐world settings, RECeUS correctly identifies both situations in which data appear appropriate for cure modeling and when data seem inappropriate for fitting cure models. [ABSTRACT FROM AUTHOR]

Background: Platform trials facilitate efficient use of resources by comparing multiple experimental agents to a common standard of care arm. They can accommodate a changing scientific paradigm within a single trial protocol by adding or dropping experimental arms—critical features for trials in rapidly developing disease areas such as COVID-19 or cancer therapeutics. However, in these trials, efficacy and safety issues may render certain participant subgroups ineligible to some experimental arms, and methods for stratified randomization do not readily apply to this setting. Methods: We propose extensions for conventional methods of stratified randomization for platform trials whose experimental arms may differ in eligibility criteria. These methods balance on a prespecified set of stratification variables observable prior to arm assignment that remains the same across experimental arms. To do so, we suggest modifying block randomization by including experimental arm eligibility as a stratifying variable, and we suggest modifying the imbalance score calculation in dynamic balancing by performing pairwise comparisons between each eligible experimental arm and standard of care arm participants eligible to that experimental arm. Results: We provide worked examples to illustrate the proposed extensions. In addition, we also provide a formula to quantify the relative efficiency loss of platform trials with varying eligibility compared with trials with non-varying eligibility as measured by the size of the common standard of care arm. Conclusions: This article presents important extensions to conventional methods for stratified randomization in order to facilitate the implementation of platform trials with differing experimental arm eligibility. [ABSTRACT FROM AUTHOR]

Background: After colorectal cancer (CRC) surgery, surveillance with colonoscopy is an important step for the early detection of local recurrence. Unfortunately, surveillance colonoscopy is underused, especially among racial/ethnic minorities. This study assesses the association between patient and neighborhood factors and receipt of surveillance colonoscopy. Methods: This retrospective, population‐based cohort study used Surveillance, Epidemiology, and End Results–Medicare linked data (2009‐2014). Beneficiaries with surgically resected stage II or III CRC between the ages of 66 and 85 years were identified, and multivariable logistic regression was used to assess the effect of factors on receipt of colonoscopy. Results: Overall, 57.5% of the patients received initial surveillance colonoscopy. After adjustments for all factors, Blacks and Hispanics had lower odds of receiving colonoscopy than non‐Hispanic Whites (NHWs; 29.6% for Blacks; P =.002; 12.9% for Hispanics; P >.05). NHWs with Medicaid coverage had 35% lower odds of surveillance colonoscopy than NHWs without Medicaid coverage. Minority patients with Medicaid were more likely to receive colonoscopy than their racial/ethnic counterparts without Medicaid coverage (P >.05). Hispanics residing in neighborhoods with incomes of ≥$90,000 had significantly lower odds of surveillance colonoscopy than Hispanics residing in neighborhoods with incomes of $0 to $30,000. Conclusions: Receipt of initial surveillance colonoscopy remains low, and there are acute disparities between Black and NHW patients. The association between factors that assess a patient's ability to access colonoscopy and actual receipt of colonoscopy suggests inequitable access to surveillance colonoscopy within and across racial/ethnic groups. There are disparities in the receipt of initial surveillance colonoscopy between Black and non‐Hispanic White patients. The association between factors that assess a patient's ability to access colonoscopy and actual receipt of colonoscopy suggests inequitable access to surveillance colonoscopy within and across racial/ethnic groups. [ABSTRACT FROM AUTHOR]