Abstract P5-13-03: The Influences of Co-Morbidities and Age on Risk of Death without Recurrence: A Retrospective Analysis of the ATAC Trial
Authors: Ring AE , Sestak I , Baum M , Howell A , Buzdar A , Dowsett M , Forbes JF , Cuzick J. 
Published: April 2011

Background: One third of breast cancers are now diagnosed in women aged 70 or over. With its high median age at study entry (64 years) the ATAC study (1) represents an opportunity to characterise tumour and treatment characteristics of a cohort of older women with early breast cancer. It also enables us to examine the effects co-morbidities and age on competing causes of mortality which could have a significant influence on adjuvant treatment decisions.

Materials and Methods: Details of trial design, methods and outcome have been published in detail elsewhere (1). The current analysis was based on the 100-month median follow-up data in the safety population in the two monotherapy arms (anastrozole N=3092, tamoxifen N=3094). Baseline co-morbidities, tumour and treatment characteristics were comparedbetween those aged &lt;70 and ≥70 years. The cumulative incidence of breast cancer-related mortality (death after recurrence) and non-breast cancer-related mortality (death without recurrence) was assessed according to histological variables, age and co-morbidities (coded according to the Satariano, Charlson and Hypertension-augmented Charlson indices).

Results: 1662 patients (27%) were aged 70 or over at study entry. Women aged 70 or over had larger tumours compared with younger women (≥2cm: 56.8 vs. 67.6%, OR 0.63, [95%CI 0.56-0.71]). Older women were more likely to undergo mastectomy (OR 1.92 [95%CI 1.71-2.16]), less likely to receive radiotherapy (OR 0.49 [95%CI 0.44-0.55]), or chemotherapy (OR 0.24 [95%CI 0.18-0.29]). Women aged 70 or over had higher rates of co-morbidities irrespective of index used. Women aged 70 or over had an increased risk of recurrence compared with those less than 70: 20.2% vs. 18.7% (HR 1.21, [95%CI 1.09-1.38]), and an increased risk of death without recurrence: 17.9% vs. 5.2% (HR 4.03 [95%CI 3.39-4.78]). The risk of death without recurrence increased with increasing co-morbidity score: 5.8% vs. 14.4% vs. 21.7% for Satariano score 0, 1 and 2+ respectively (P&lt;0.0001). Similar patterns were observed for the Charlson indices, and when those aged above and below 70 were analysed separately. In those patients aged 70 or over the combined influences of nodal status and co-morbidities on deaths without recurrence were examined. In those with node negative breast cancer, non-breast cancer deaths dominated irrespective of co-morbidities. In those with node positive disease and Satariano index 0, breast cancer deaths dominated but with increasing Satariano index there were no differences between risk of breast cancer death and death from other causes.

Discussion: There are differences in tumour and treatment characteristics between older and younger patients which may explain the differences in risks of recurrence. Age and co-morbidities significantly influence the risks of death without recurrence. Formal assessment of co-morbidities should be incorporated into decisions regarding adjuvant therapies. 1. ATAC Trialists’ Group. Lancet Oncol 2008; 9: 45-53.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-13-03.