Prognostic information of a previously diagnosed sister is an independent prognosticator for a newly diagnosed sister with breast cancer
Menée en Suède auprès de 834 paires de sœurs atteintes d'un cancer du sein diagnostiqué entre janvier 1992 et décembre 2006, cette étude montre que les durées de survie des sœurs sont associées, indépendamment des autres facteurs
Background : Breast cancer survival has been shown to be associated among relatives. In this study, we used a population-based cohort of Swedish sisters, both diagnosed with breast cancer, to determine whether prognostic information of a previously diagnosed sibling is useful for the clinical management of a newly diagnosed sibling.
Patients and methods : The population-based cohort included all sister pairs, 1,617 sisters, diagnosed with breast cancer in Sweden, from January 1, 1992, through December 31, 2006, with complete follow-up. All information was collected manually from original pathology reports and patient records.
The Kappa Statistic was used to measure the agreement of primary tumor characteristics between the sisters. We modeled the breast cancer-specific survival using multivariate (Cox) proportional hazard analyses in two steps categorizing the older sister's survival.
Results : Estrogen receptor status was the only tumor characteristic significantly associated between the sisters (Kappa 0.18 [95% CI 0.089-0.27]).
Younger sisters with poor older sister survival showed significantly worse survival compared to patients with good older sister survival (P-log rank=0.017). A two-fold increased hazard ratio (HR) for death from breast cancer was found in younger sisters with poor older sister survival compared to patients with good sister survival (HR 2.56 [95% CI 1.16-5.65]), adjusting for age and calendar period of diagnosis, socioeconomic factors, number of children and hospital of primary tumor diagnosis. When further adjusting for primary tumor characteristics and adjuvant therapy, the risk for death from breast cancer in younger sisters with poor older sister survival became more pronounced (HR 3.35 [1.34-8.34]).
Conclusions : Our findings derived from a population-based cohort of Swedish sister pairs suggest that breast cancer-specific survival is inherited independent of tumor characteristics and treatment in the sibling later diagnosed with the disease. Prognostic information of a previously diagnosed sibling with breast cancer could be important in the clinical management.
Annals of Oncology , résumé, 2014