Better tools for better estimates: improving approaches to handling missing data in Swiss cancer registries

OBJECTIVE

Various approaches have been used in the literature to handle missing vital status data in cancer registries. We aimed to compare these approaches to determine which led to the least biased estimates in typical analytic tasks of cancer registries.

METHODS

A simulation study was performed using data from the Swiss National Agency for Cancer Registration for six tumor types. First, 5%, 10% and 15% missingness in the vital status were introduced artificially in the complete data. Second, missing vital status data were handled by applying no, single or multiple imputations. Five-year overall survival estimates, relative survival or standardized incidence ratio were computed. Estimates were compared with the true value.

RESULTS

Standardized incidence ratio estimates for colorectal cancer obtained with multiple imputation yielded least biased results (-0.06 to -0.04), but the widest confidence intervals. Single imputation was more biased (-0.32) than using no imputation at all (-0.21). A similar pattern was observed for overall survival and relative survival.

CONCLUSION

This simulation study indicated that often used single imputation (sometimes referred to as simulating follow-up times) techniques to fill in missing vital status data are likely too biased to be useful in practice. Multiple imputation approaches yielded standardized incidence ratio, overall and relative survival estimates with the least bias, indicating reasonable performance that is likely to generalize to other settings.

Which Aspirin Dose and Preparation Is Best for the Long-Term Prevention of Cardiovascular Disease and Cancer? Evidence From a Systematic Review and Network Meta-Analysis

The evidence base on aspirin in primary prevention suggests that it can reduce significantly the risk of cardiovascular disease (CVD) events and cancer, especially colorectal, albeit increasing bleeding. There is, however, uncertainty on the optimal aspirin dose and preparation for primary prevention. We thus aimed to review main sources of evidence informing on daily dosage and preparation of aspirin for primary prevention of CVD and cancer. We collected and elaborated aspirin effectiveness and safety data from U.S. Preventive Services Task Force reports on aspirin in primary prevention, distinguishing average daily dose in <100mg, 100mg, and >100mg. The following preparations were also systematically compared: enteric coated, controlled release, non-coated, or otherwise unspecified. Fixed-effect pairwise and network meta-analytic models were run in a frequentist framework. Eleven randomized trials were shortlisted, enrolling 104,101 subjects, followed for a median of 60months. At pairwise analysis, aspirin was associated with significant reductions in death and CVD events, non-significant reductions in cancer death or incidence, and significant increases in the risk of intracranial and gastrointestinal (GI) bleeding. An average daily dose of 100mg had the highest probability of reducing death, cancer death, and cancer incidence, whereas higher doses seemed superior for reducing CVD events, and 100mg or less daily proved better tolerated. Coated preparations appeared more beneficial for death, cancer death, cancer incidence, and GI bleeding, whereas controlled release preparations appeared better for CVD events and non-coated ones for intracranial bleeding. In conclusion, an average daily dose of 100mg of coated aspirin seems more likely to confer favorable preventive effects on death and cancer, with higher doses more appealing for CVD prevention and lower doses better tolerated.