A population based study of radiotherapy in a cohort of patients with breast cancer diagnosed between 1996 and 2000

We studied the use of radiotherapy (RT) (especially secondary RT) in a cohort of 6561 patients in southern Netherlands with invasive breast cancer diagnosed between 1996 and 2000 (median follow-up: 66 months, range 0-107 months). Radiation within 6 months of diagnosis was considered primary RT (PRT). RT given 6 months or later after diagnosis or after PRT was considered secondary RT (SRT). Of all patients, 67% received RT, 3554 only PRT, 323 only SRT and 503 both. The cumulative use of SRT at 100 months was 17%. The 826 patients receiving SRT underwent 1846 courses 0-105 months (median 36) after diagnosis; the retreat rate was 35%. Elderly patients received SRT significantly less often (OR(age50-69)=0.7, 95%CI=0.6-0.8, OR(age> or 70)=0.4, 95%CI=0.3-0.5). The following factors increased the chance for SRT: patients from the eastern region (OR=1.3, 95%CI=1.1-1.6); patients who received PRT (OR=1.3, 95%CI=1.0-1.5) and patients who underwent mastectomy including axillary node dissection as well as unresected patients (OR=1.9, 95%CI=1.5-2.4, OR=2.6, 95%CI=1.7-3.9, respectively). Thirteen percent of all patients with breast cancer received SRT, with a large variation in age and between the 2 RT departments in the region.