Factors influencing the quality of local management of ductal carcinoma in situ: a cohort study

Background: Guidelines recommend radiotherapy (rt) after breast-conserving surgery (bcs) for optimal control of ductal carcinoma in situ (dcis). The aim of the present study was to characterize the rates of rt consideration and administration, and to identify factors influencing those rates in a cohort of women diagnosed between 1998 and 2005 in Quebec.

Methods: Quebec's medical service claims and discharge abstract database were used. Using consultation for rt as an indicator for rt consideration, odds ratios (ors) and 95% confidence intervals (cis) were estimated using a generalized estimating equations regression model.

Results: Of 4139 women analyzed (mean age: 58 years), 3435 (83%) received a consultation for rt, and 3057 of them (89%) proceeded with treatment. The rate of rt consideration increased by 7.1% over the study period, with notable differences in the various age groups. Relative to women 50-69 years of age, the ors for being considered for rt were, respectively, 0.89 (95% ci: 0.71 to 1.12), 0.71 (95% ci: 0.55 to 0.92), and 0.20 (95% ci: 0.14 to 0.31) for women younger than 50, 70-79, and 80 years of age and older. Distance to a designated breast care centre lowered the probability of rt consideration, but the presence of comorbidities did not. A surgeon's volume of bcss increased the probability of being considered for rt by 7% for every 10 such procedures performed (or: 1.07; 95% ci: 1.04 to 1.11).

Conclusions: Consideration for rt has increased over time. However, older women (despite being in good health) and those living far from a designated breast care centre or having a low-case-volume surgeon were less likely to be considered for rt.