Old age is associated with comorbidity and decreased functioning which influences treatment decisions in elderly breast cancer patients. The purpose of this study was to identify risk factors for complications after breast cancer surgery in elderly patients, and to assess mortality in patients with postoperative complications. The FOCUS cohort is a detailed retrospective cohort of all breast cancer patients aged 65 years and older who were diagnosed between 1997 and 2004 in the South-West of the Netherlands. Risk factors for postoperative complications were assessed using univariable and multivariable logistic regression models. One-year survival and overall survival were calculated using univariable and multivariable Cox Regression models, and relative survival was calculated according to the Ederer II method. 3179 patients received surgery, of whom 19 % (n = 618) developed 1 or more postoperative complication(s). The odds ratio of having postoperative complications increased with age [OR 1.85 (95 % confidence interval (CI) 1.37-2.50, p = 0.001) in patients >85 years] and number of concomitant diseases [OR 1.71 (95 % CI 1.30-2.24, p ≤ 0.001) for 4 or more concomitant diseases]. One-year overall survival, overall survival, and relative survival were worse in patients with postoperative complications [multivariable HR 1.49 (95 % CI 1.05-2.11), p = 0.025. HR 1.21, (95 % CI 1.07-1.36), p = 0.002 and RER 1.19 (95 % CI 1.05-1.34), p = 0.006 respectively]. Stratified for comorbidity, relative survival was lower in patients without comorbidity only. Increasing number of concomitant disease increased the risk of postoperative complications. Although elderly patients with comorbidity did have a higher risk of postoperative complications, relative mortality was not higher in this group. This suggests that postoperative complications in itself did not lead to higher relative mortality, but that the high relative mortality was most likely due to geriatric parameters such as comorbidity or poor physical function.

An important consideration in studies that use cause-specific endpoints such as cancer-specific survival or disease recurrence is that risk of dying from another cause before experiencing the event of interest is generally much higher in older patients. Such competing events are of major importance in the design and analysis of studies with older patients, as a patient who dies from another cause before the event of interest cannot reach the endpoint. In this Commentary, we present several clinical examples of research questions in a population-based cohort of older breast cancer patients with a high frequency of competing events and discuss implications of choosing models that deal with competing risks in different ways. We show that in populations with high frequency of competing events, it is important to consider which method is most appropriate to estimate cause-specific endpoints. We demonstrate that when calculating absolute cause-specific risks the Kaplan-Meier method overestimates risk of the event of interest and that the cumulative incidence competing risks (CICR) method, which takes competing risks into account, should be used instead. Two approaches are commonly used to model the association between prognostic factors and cause-specific survival: the Cox proportional hazards model and the Fine and Gray model. We discuss both models and show that in etiologic research the Cox Proportional Hazards model is recommended, while in predictive research the Fine and Gray model is often more appropriate. In conclusion, in studies with cause-specific endpoints in populations with a high frequency of competing events, researchers should carefully choose the most appropriate statistical method to prevent incorrect interpretation of results.

Background Older patients are poorly represented in breast cancer research and guidelines do not provide evidence based recommendations for this specific group. We compared treatment strategies and survival outcomes between European countries and assessed whether variance in treatment patterns may be associated with variation in survival. Methods Population-based study including patients aged ≥ 70 with non-metastatic BC from cancer registries from the Netherlands, Belgium, Ireland, England and Greater Poland. Proportions of local and systemic treatments, five-year relative survival and relative excess risks (RER) between countries were calculated. Results In total, 236,015 patients were included. The proportion of stage I BC receiving endocrine therapy ranged from 19.6% (Netherlands) to 84.6% (Belgium). The proportion of stage III BC receiving no breast surgery varied between 22.0% (Belgium) and 50.8% (Ireland). For stage I BC, relative survival was lower in England compared with Belgium (RER 2.96, 95%CI 1.30–6.72, P < .001). For stage III BC, England, Ireland and Greater Poland showed significantly worse relative survival compared with Belgium. Conclusions There is substantial variation in treatment strategies and survival outcomes in elderly with BC in Europe. For early-stage BC, we observed large variation in endocrine therapy but no variation in relative survival, suggesting potential overtreatment. For advanced BC, we observed higher survival in countries with lower proportions of omission of surgery, suggesting potential undertreatment.

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Breast cancer trial participants aged 75 years or older do not represent elderly breast cancer patients of corresponding age from the general population, which hampers the external validity of a trial.