Studies comparing the prognosis after contralateral breast cancer (CBC) with that after unilateral breast cancer (UBC) shows conflicting results. We assessed the risk of breast cancer-specific death for women with metachronous CBC compared to those with a UBC in 8,478 women with invasive primary breast cancer registered in the Guy's and St. Thomas' Breast Cancer Tissue and Data Bank. Risk factors associated with breast cancer-specific death for women with CBC were estimated using Cox proportional hazards modelling. Prognoses after UBC and CBC were compared, with survival time for women with CBC calculated: (i) from CBC, (ii) from the initial cancer with CBC as a time-dependent covariate. Women diagnosed with CBC within 5 years after the initial primary breast cancer had a worse prognosis than those with CBC after 5 years and those with UBC. Women with CBC who had positive lymph nodes at the initial breast cancer diagnosis were at an increased risk of dying from breast cancer compared to those without [HR 2.5 (95% CI 1.5-4.0)]. For all stages of the initial breast cancer, a worse prognosis was observed after CBC. CBC increased the hazard originating from the initial cancer at any follow-up time, but the highest hazards were associated with a short interval to CBC. Metachronous CBC adds to the risk of dying from breast cancer. The risk increases substantially when it occurs shortly after the initial cancer, indicating a CBC in some instances may be an indicator of active distant disease. The occurrence of CBC implies a new surveillance and therapeutic situation.
Women with advanced-stage primary breast cancer had an increased risk of developing CBC. CBC is associated with an increased risk of dying from breast cancer throughout a long period of follow-up after the primary tumor. Our findings suggest that the event of CBC marks a new clinical situation in terms of investigations for metastases, treatment considerations, and follow-up strategy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.