Comparison of Methods for Measuring Radiotherapy Utilisation

Evidence-based estimates of appropriate rates of radiotherapy utilisation are usually stated as the proportion of cancer patients who should receive radiotherapy at least once in their lifetime. However, the prolonged follow-up required to measure the lifetime radiotherapy rate limits its value in monitoring access to radiotherapy in routine practice. The objectives of this study were to evaluate shorter-term methods for measuring radiotherapy utilisation and to determine how well they predict the lifetime radiotherapy rate.

The Ontario Cancer Registry provided records of all cases of cancer diagnosed in Ontario between 1984 and 2015. Records of all radiotherapy delivered by Ontario cancer centres were linked to individual cases in the Ontario Cancer Registry. Patients were followed forward for 20 years to determine the relationship between short-term and long-term rates of use of radiotherapy. Radiotherapy utilisation was also estimated by comparing total radiotherapy workload with cancer incidence; these measures were compared with observed long-term radiotherapy rates.

The rate of use of radiotherapy within 1 year of diagnosis (RT_1y) was strongly predictive of the rate of use of radiotherapy after 20 years (RT_20y); for each annual cohort of cases between 1984 and 1995, RT_20y was approximately equal to 1.3 × RT_1y. The number of cases treated for the first time with radiotherapy in a specified period, divided by the number of new cases diagnosed in the same period, was about equal to the proportion of cases treated with radiotherapy within 20 years of diagnosis (RT_20y).

The lifetime rate of use of radiotherapy may be predicted quite accurately from the rate observed within 1 year of diagnosis, or from the ratio of new cases treated to cancer incidence in a specified period. Either of these measures may therefore be used to audit radiotherapy utilisation against the existing evidence-based targets.