676 at all. Despite large treatment differences, survival does not seem to be affected in a major way. Keywords Breast cancer Elderly Surgery Treatment Survival Population-based Introduction Breast cancer is the most frequently diagnosed cancer worldwide, accounting for 23% of all new cancer cases in women and 14% of all female cancer deaths in 2008 [1]. A high incidence of breast cancer is observed in women aged 65 years and older, comprising over 40% of all breast cancer patients in developed countries [2]. Given the aging population and constantly improving screening and diag- nostic tools, the number of elderly patients with breast cancer is expected to grow in the coming decades [3]. Clinical trials indicate that the choice of mastectomy versus breast conserving surgery (BCS) followed by radiotherapy (RT) for early stage breast cancer does not affect overall mortality or breast cancer mortality [4, 5]. However, patients who receive BCS ? RT have a small but signiﬁcant increase in local recurrences. Elderly patients have been under-represented in breast cancer treatment trials, based on their age, comorbid diseases, and logistic barriers [2, 6]. Consequently it is questionable if trial results can be generalized to patients of all ages. Despite guideline recommendations, several observational studies from different countries show that with increasing age, treatment of early stage breast cancer more often consists of mastectomy; moreover, omission of RT after BCS increases with increasing age [3, 7–11]. In addition, older breast cancer patients are more likely than younger patients to not undergo breast surgery, even though mor- tality caused by breast surgery is shown to be low among elderly [12]. The different treatment approaches to elderly breast cancer patients could have consequences. Several obser- vational studies showed worse overall, breast cancer spe- ciﬁc, and disease-free survival for ‘undertreated’ elderly patients (not treated according to guidelines) [13, 14]. An international study comparing breast surgery among countries for patients participating in the Tamoxifen exe- mestane adjuvant multinational (TEAM) trial showed large differences in surgical treatment approach to early stage breast cancer in postmenopausal women [15]. The EU- ROCARE group recently published a population-based study on the surgical treatment of early stage breast cancer (T1N0M0) across Europe. They found considerable dif- ferences in the use of BCS followed by RT. Of all surgi- cally treated patients across the participating countries, 55% received BCS ? RT, with a range from 9% in Estonia 123 Breast Cancer Res Treat (2012) 132:675–682 to 78% in France [11]. However, none of these studies speciﬁcally compared treatment of the elderly patient with breast cancer. The aim of this study is to make an inter- national comparison of breast and axillary surgery, and radiotherapy after breast conserving surgery in elderly patients with early stage breast cancer, and its possible inﬂuence on survival. Methods Patients Women aged 65 and older, who were diagnosed with early stage breast cancer (T0-2, N0-1, M0) and recorded in population-based cancer registries in the Netherlands, Ire- land, Switzerland, Belgium, Germany, Portugal, and the U.S. were included. From the population-based database of the Netherlands Cancer Registry, women diagnosed between 1995 and 2005 were selected. For the US, patients diagnosed between 1998 and 2007 were selected from the Surveillance, Epidemiology, and End Results (SEER) database covering 28% of the US population. In Switzer- land, patients diagnosed between 2003 and 2005 were identiﬁed from seven population-based cancer registries (Geneva, Valais, Ticino, St Gallen-Appenzell, Grisons- Glarus, Basel city and countryside, and Zurich) covering 47% of the Swiss population. In Ireland, patients were selected from the national cancer registry between 1999 and 2007. In Belgium, patients diagnosed between 2001 and 2006 were selected from the national cancer registry. German patients diagnosed between 1995 and 2008 in the Munich region were selected. Finally, patients from the Portugal South regional cancer registry (ROR-Sul) were selected between 2006 and 2008. Patients with a diagnosis of breast cancer on death certiﬁcate or at autopsy only or with unknown treatment were excluded. Statistics Calculations of treatment percentages and survival were performed for each country and aggregated into tables for the comparison between countries. Patients were catego- rized in six age groups (65–69, 70–74, 75–79, 80–84, 85–89, and C90) for the treatment analyses. Tumor stage was deﬁned by combined TNM stage [16] (categorized as stage I, IIA, IIB), with clinical stage used when patholog- ical stage was missing. Stage I includes T1N0 tumors, stage IIA T1N1, or T2N0 tumors and stage IIB contains T2N1 tumors (also T3N0 tumors but these were excluded from this study). Breast surgery was categorized as mas- tectomy, breast conserving surgery, or no surgery. Patients who received BCS ﬁrst, but later received mastectomy,