The pattern of metastatic spread among breast cancer sub-types.

Abstract

Abstract Abstract #2025 Background: Although breast cancer subtypes are associated with differing relapse risks, the patterns of metastatic spread are less well defined, particularly for more than the first site of metastasis. We describe the sites of all diagnosed metastases among breast cancer subtypes in a large series of women diagnosed with breast cancer to further define patterns of spread.
 Methods: Subjects with early stage breast cancer referred to the British Columbia Cancer Agency from 1986 to 1992 were included. Archival paraffin tissue blocks were used to construct a tissue microarray. Breast cancer subtypes were defined as Luminal A (ER/PR+ and HER2- and Ki67 <19%), Luminal B (ER/PR+, and HER2- and Ki67 >19%), LuminalHer2 (Her2+ and ER/PR+), HER2 (HER2+ and ER- and PR-), and Basal (HER2-ER-PR- and CK 5/6+and/orEGFR+). All documented sites of distant metastasis were abstracted by chart review according to predefined categories.
 Results: 3526 eligible women were classified according to Luminal A (2109), Luminal B (514), LuminalHER2 (252), HER2 (276) and Basal (375) and 30%,47%, 48%, 50% and 42% in each subgroup were diagnosed with distant metastasis. Median Survival with metastatic disease was 2.2, 1.6 and 1.3 years in Luminal A, B and LuminalHER2 groups and 0.7 and 0.5 years in the HER2 and Basal types, respectively. Bone was the predominant site of metastasis for luminal groups A (76%), B (73%) and LuminalHER2 (70%). The distribution was more heterogeneous in HER and Basal groups. High rates of brain metastasis were observed in the HER2 (30%) and Basal (27%) and less frequently in the LuminalHER2 (17%) and other groups (p <0001).
 
 Conclusion: Molecular breast cancer subtypes are associated with specific distributions of metastasis which may lead to specific prophylactic therapies to modify this risk. New systemic therapies, including trastuzumab, may impact these patterns and survival after recurrence. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2025.