Comparison of four methods for estimating actual radiotherapy utilisation using the 45 and Up Study cohort in New South Wales, Australia

Aim: To compare four methods for estimating actual radiotherapy utilisation (A-RUR) reported in the literature. Materials and methods: Participants in the 45 and Up Study in New South Wales (NSW) Australia completed a baseline questionnaire during 2006–2009 and consented to record linkage with administrative health datasets. Incident primary cancers (2006–2010) were identified through linkage with the NSW Cancer Registry. Radiotherapy receipt was identified through linkage with the Medicare Benefits Schedule and/or NSW Admitted Patient Data Collection (2006–2014). The four methods for estimating A-RUR were: 1 – crude proportion; 2 – crude proportion for patients followed for a defined period; 3 – life table without censoring of deaths; 4 – life table with censoring of deaths. Results: There were 9817 participants with a diagnosis of cancer between recruitment and end of 2010, median follow-up 5.4 years. Crude A-RUR for the cancer cohort was 30.2%, below the “optimal” 48%. The 5 yr A-RUR was 29.7%, 29.8% and 33.4% using methods 2–4 respectively. Conclusions: A-RUR estimates differed depending on the method used and all were below optimal. The method for estimating A-RUR for future studies should depend on the availability of the data as well as the intended audience for the results.