Characteristics of patients with missing information on stage: a population-based study of patients diagnosed with colon, lung or breast cancer in England in 2013

Background:Stage is a key predictor of cancer survival. Complete cancer staging is vital for understanding outcomesat population level and monitoring the efficacy of early diagnosis initiatives. Cancer registries usually collect details ofthe disease extent but staging information may be missing because a stage was never assigned to a patient orbecause it was not included in cancer registration records. Missing stage information introduce methodologicaldifficulties for analysis and interpretation of results. We describe the associations between missing stage andsocio-demographic and clinical characteristics of patients diagnosed with colon, lung or breast cancer in Englandin 2013. We assess how these associations change when completeness is high, and administrative issues areassumed to be minimal. We estimate the amount of avoidable missing stage data if high levels of completenessreached by some Clinical Commissioning Groups (CCGs), were achieved nationally.Methods:Individual cancer records were retrieved from the National Cancer Registration and linked to theRoutes to Diagnosis and Hospital Episode Statistics datasets to obtain additional clinical information. We usedmultivariable beta binomial regression models to estimate the strength of the association between socio-demographic and clinical characteristics of patients and missing stage and to derive the amount of avoidablemissing stage.Results:Multivariable modelling showed that old age was associated with missing stage irrespective of thecancer site and independent of comorbidity score, short-term mortality and patient characteristics. Thisremained true for patients in the CCGs with high completeness. Applying the results from these CCGs to thewhole cohort showed that approximately 70% of missing stage information was potentially avoidable.Conclusions:Missing stage was more frequent in older patients, including those residing in CCGs with highcompleteness. This disadvantage for older patients was not explained fully by the presence of comorbidity. Asubstantial gain in completeness could have been achieved if administrative practices were improved to thelevel of the highest performing areas. Reasons for missing stage information should be carefully assessedbefore any study, and potential distortions introduced by how missing stage is handled should be consideredin order to draw the most correct inference from available statistics.