Correlates and effect of suboptimal radiotherapy in women with ductal carcinoma in situ or early invasive breast cancer

Abstract

The study aimed to identify factors associated with less-than-optimal radiotherapy (RT) and its impact on disease-free survival in women aged 66+ years diagnosed with stage I breast cancer or ductal carcinoma in situ (DCIS). The subjects were women diagnosed from 1991 to 1999 in the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database who underwent breast-conserving surgery and RT within 12 months postdiagnosis. The authors conducted descriptive and multivariate survival analyses, and considered age, race, poverty, marital status, comorbidity indices, rural/urban, radiation oncologist density, comedo necrosis histology (DCIS only), chemotherapy receipt (stage I only), and RT completion (3+ weeks of treatment) and delay (8+ weeks postsurgery without chemotherapy; 4+ weeks postchemotherapy). Of 7791 subjects, 16% experienced RT delay, and 3% had incomplete RT. Subjects with stage I disease who were more likely to delay RT were of black race (odds ratio [OR], 1.56; 95% confidence interval [CI], 1.17-2.08), whereas women in areas of high radiation oncologist density were less likely to delay (OR, 0.73; 95% CI, 0.66-0.81). Those living in high poverty areas were less likely to complete RT (P < .03), as were those undergoing chemotherapy (OR, 1.82; 95% CI, 1.15-2.88). Stage I breast cancer patients with delayed RT were more likely to experience a subsequent breast event (OR, 1.14; 95% CI, 1.00-1.30), and those with incomplete RT had a higher rate of overall mortality (OR, 1.32; 95% CI, 1.06-1.63). Factors associated with lower subsequent breast events included older age, lower poverty, and being married. RT delays of 12+ weeks (or 8+ weeks postchemotherapy) had a strongly negative impact on subsequent events (OR, 3.94; 95% CI, 2.51-6.17 for DCIS; OR, 2.77; 95% CI, 1.84-2.59 for stage I). RT should be facilitated to ensure completion and timeliness, especially for early invasive breast cancer patients.