Population-based utilization of radiation therapy by a Canadian breast cancer cohort.

We examined trends in radiation therapy (rt) utilization by a population-based breast cancer cohort in Ontario. The provincial cancer registry provided a breast cancer cohort based on diagnosis dates from April 1, 2005, to March 31, 2010. Staging information was also available. The cohort was then linked, by encrypted health card number, to linkable administrative datasets, including rt utilization. The average age in the identified female breast cancer cohort (n = 39,656) was 61.6 ± 14.0 years. Almost two thirds of the patients (n = 25,225) received rt, and staging information was available for 22,988 patients (9541 stage i, 8516 stage ii, 4050 stage iii, and 881 stage iv). The average number of rt courses received by the patients was 1.4 ± 0.7 for stage i, 1.8 ± 1.1 for stage ii, 2.5 ± 1.3 for stage iii, and 2.8 ± 2.4 for stage iv. The ratio of conventional rt to intensity-modulated rt was 70.9%:16.6% for stage i, 71.6%:11.3% for stage ii, 74.6%:4.6% for stage iii, and 89.6%:2.2% for stage iv. From 2005 to 2010, almost two thirds of a Canadian female breast cancer cohort received rt, and the average number of courses increased with disease severity. A similar trend was observed with the type of rt (use of conventional rt increased with disease severity). The next step is to apply unit costs to the number of fractions and to obtain rt planning and radiation therapist times.