Estimating long-term mortality in women with hormone receptor-positive breast cancer: The 'ESTIMATE' tool.

Purpose: The risk of breast cancer-specific mortality (BCSM) persists for at least 20 years from diagnosis. Estimating the risk of BCSM over this extended period along with competing risks of death would aid clinical decision-making. We aimed to develop an interactive tool called 'ESTIMATE', to explore the Surveillance, Epidemiology, and End Results (SEER) registry to quantify residual risks of BCSM, non-BCSM and all-cause mortality in non-metastatic, hormone receptor (HR)-positive breast cancer patient subgroups at any given time after diagnosis, up to 20 years.

Methods: Using SEER data, we included 264,237 women with invasive, non-metastatic, HR-positive breast cancer diagnosed from 1990 to 2006. We developed a tool that provides a nonparametric estimate of the residual cumulative risk of BCSM and non-BCSM by year 20 after any specified time from initial diagnosis, among patients defined by baseline clinical and pathologic variables, using Gray's subdistribution method.

Results: ESTIMATE allows the user to input patient and tumour characteristics and the preferred timeframe. For example, patients in the age group of 40-49 diagnosed with T1cN1, grade II breast cancer who survived 7 years, have a 14% (95% confidence interval [CI]: 11.9%-16.1%) residual cumulative risk of BCSM in the next 13 years, and a 6.4% (95% CI: 4.7%-8.1%) residual cumulative risk of non-BCSM over the same period.

Conclusions: ESTIMATE provides population-based risks of BCSM, non-BCSM and all-cause mortality through 20 years after diagnosis of HR-positive breast cancer, based on patient and tumour characteristics. ESTIMATE can inform discussions about prognosis, a balance between competing risks and aid clinical decision-making.