Cancer outcomes in women without upfront surgery for ductal carcinoma in situ: observational cohort study
Objective To determine the risk of subsequent ipsilateral invasive breast cancer in women who do not receive upfront surgery on diagnosis of ductal carcinoma in situ (DCIS). Design Observational cohort study using data abstracted directly from patients’ medical records and from a national cancer registry in patients with primary DCIS diagnosed between 2008 and 2015. Setting Commission on Cancer accredited facilities (n=1330) in the US. Participants 1780 women with diagnosis of primary DCIS on needle biopsy who were alive and free of invasive breast cancer at 6 months after diagnosis. Interventions No surgery within 6 months of diagnosis. Main outcome measures Primary outcome: ipsilateral invasive breast cancer; secondary outcome: death due to breast cancer. Subgroup analysis by risk status, based on eligibility criteria of ongoing active monitoring trials: low risk if aged ≥40 years at diagnosis of an imaging detected, nuclear grade I/II, and hormone receptor positive DCIS; high risk o
