Abstract P6-06-48: Breast cancer subtypes and metastatic pattern at the Regional Breast Center Dresden
Authors: Kast K , Link T , Friedrich K , Petzold A , Niedostatek A , Werner C , Werner A , Baretton GB , Klug SJ , Wimberger P 
Published: August 2014

Background: Breast cancer is classified into the subtypes luminal A, luminal B (HER2 positive or negative), HER2 enriched (not luminal) and triple negative (St. Gallen International Breast Cancer Conference 2011). These breast cancer subtypes show differences in response to therapies and prognosis. Amongst others prognosis is depended on hormone receptor positivity, extent and localization of metastases. Routine screening for metastatic disease is not part of the guidelines for breast cancer aftercare although in oligometastatic disease surgery or local ablative therapies can be used to improve outcome. We evaluated if tumor aftercare should be individualized due to different patterns of metastases of the breast cancer subtypes.

Methods: Four hospitals incorporated into the Regional Breast Center Dresden as a certified center of excellence for treating breast cancer. We retrospectively evaluated sites and characteristics of metastases and survival data according to the intrinsic breast cancer subtypes from patients treated between 2006 and 2011. Immunohistochemical detection of estrogen and progesterone receptor, grading and overexpression of HER2 oncogene was used for identifying tumor subtypes. All data were collected at the Clinical Cancer Registry Dresden.

Results: In 2006 routinely identification of overexpression of HER2 started. Since that time 2334 patients had therapy for breast cancer- 12,4% (290/2334) with metastatic disease (7.2%; 168/2334 primary and 5.2%; 122/2334 relapse). Mean duration of follow up was 38 months. Metastatic disease was more frequently found in HER2 enriched, 27.2%; 30/110, and triple negative, 19.7%; 44/223, than in the luminal subtypes: luminal A 8.3%; 107/1284, luminal B HER2 negative 12.2%; 23/188, luminal B HER2 positive 16%; 36/225. Luminal A and B HER2 negative subtypes showed a preference for solely bone metastases (43%; 56/130) which was rare in triple negative breast cancer (6.8% 3/44). If bone metastases occurred in triple negative breast cancer they mostly appeared together with visceral and/or brain metastatic disease (27%; 12/44). Solely visceral metastases were found in the HER2 enriched subtype (46.7%; 14/30), luminal B HER2 positive (38.9%; 14/36), and triple negative breast cancer (20.2%; 19/44). Brain metastases were more frequently observed in triple negative breast cancer (22.7%; 10/44). Overall survival rate at 5 years for metastatic disease was 38.5% (95%CI 28.2-52.5) for luminal A, 23.1% (95%CI 12.0-44.5) for luminal B (HER2 negative), 11.9% (95%CI 5.5-25.7) for luminal B (HER2 positive), 27.6% (95%CI 14.4-52.8) for HER2 enriched and 6.5% (95%CI 2.4-17.1) for triple negative subtype.

Conclusion: Different patterns of metastatic disease were seen according to the subtypes of breast cancer. An individualized tumor aftercare that includes screening for visceral metastasis might improve prognosis of patients with luminal B HER positive, HER enriched and triple negative subtype. Further investigation on patients eligible for metastatic surgery should be performed with longer follow up and evaluated with respect to post-interventional survival.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-48.