Abstract
Previous studies generally indicate that synchronous bilateral breast cancers (SBBC) have an equivalent or moderately poorer survival compared with unilateral cases. The prognostic characteristics of SBBC would be relevant when planning adjuvant therapies and follow-up medical surveillance. The frequency of SBBC among early breast cancers in clinical settings in Australia and New Zealand were investigated, plus their prognostic significance, using the Breast Cancer Audit Database of the Society of Breast Surgeons of Australia and New Zealand, which covered an estimated 60% of early invasive lesions in those countries. Rate ratios (95% confidence limits) of SBBC were investigated among 35,370 female breast cancer cases by age of woman, histology type, grade, tumour diameter, nodal status, lymphatic/vascular invasion and oestrogen receptor status. Univariate and multivariable disease-specific survival analyses were undertaken. 2.3% of cases were found to be SBBC (i.e., diagnoses occurring within 3 months). The figure increased from 1.4% in women less than 40 years to 4.1% in those aged 80 years or more. Disease-specific survivals did not vary by SBBC status (p=0.206). After adjusting for age, histology type, diameter, grade, nodal status, lymphatic/vascular invasion, and oestrogen receptor status, the relative risk of breast cancer death for SBBC was 1.17 (95% CL: 0.91, 1.51). After adjusting for favourable prognostic factors more common in SBBC cases (i.e., histology type, grade, lymphatic/ vascular invasion, and oestrogen receptor status), the relative risk of breast cancer death for SBBC was 1.42 (95% CL: 1.10, 1.82). After adjusting for unfavourable prognostic factors more common in SBBC cases (i.e., older age and large tumour diameter), the relative risk of breast cancer death for SBBC was 0.98 (95% CL: 0.76, 1.26). Results confirm previous findings of an equivalent or moderately poorer survival for SBBC but indicate that SBBC status is likely to be an important prognostic indicator for some cases.
Highlights
The objective of this study is to determine from the Breast Cancer Audit database the prevalence of synchronous bilateral breast cancers (SBBC) among early breast cancers, whether survival differences exist by SBBC status after adjusting for age and conventional clinical risk factors, and based on results, to assess whether SBBC status should be included in statistical models for predicting survivals of women treated at participating Breast Cancer Audit practices
The relative risk (95% confidence limits) of breast cancer death for SBBC compared with unilateral cases was 1.18 (0.91, 1.51)
The five-year disease-specific survival of 93% for all breast cases in this study equates with the 93% reported for the Australian Capital Territory (ACT)/South Eastern New South Wales (SENSW) (Beckmann et al, 2011)
Summary
Evidence of the prognostic significance of synchronous bilateral compared with unilateral breast cancer is available from a number of studies (Gollamudi et al, 1997; Heron et al, 2000; Kollias et al, 2001; Newman et al, 2001; Jobsen et al, 2003; Polednak, 2003; Tousimis, 2005; Beckmann et al, 2011). Most indicate that synchronous bilateral breast cancers (SBBC) have either an equivalent or moderately poorer survival compared with unilateral cases. Previous studies generally indicate that synchronous bilateral breast cancers (SBBC) have an equivalent or moderately poorer survival compared with unilateral cases. Design: Rate ratios (95% confidence limits) of SBBC were investigated among 35,370 female breast cancer cases by age of woman, histology type, grade, tumour diameter, nodal status, lymphatic/vascular invasion and oestrogen receptor status. After adjusting for age, histology type, diameter, grade, nodal status, lymphatic/vascular invasion, and oestrogen receptor status, the relative risk of breast cancer death for SBBC was 1.17 (95% CL: 0.91, 1.51). After adjusting for favourable prognostic factors more common in SBBC cases (i.e., histology type, grade, lymphatic/ vascular invasion, and oestrogen receptor status), the relative risk of breast cancer death for SBBC was 1.42 (95% CL: 1.10, 1.82). Conclusions: Results confirm previous findings of an equivalent or moderately poorer survival for SBBC but indicate that SBBC status is likely to be an important prognostic indicator for some cases
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