Phylogenetic reconstruction of breast cancer reveals two routes of metastatic dissemination associated with distinct clinical outcome

• Main Authors: David Venet, Danai Fimereli, Françoise Rothé, Bram Boeckx, Marion Maetens, Samira Majjaj, Ghizlane Rouas, Maria Capra, Giuseppina Bonizzi, Federica Contaldo, Christine Galant, Martine Piccart, Giancarlo Pruneri, Denis Larsimont, Diether Lambrechts, Christine Desmedt, Christos Sotiriou
• Format: Article
• Language: English
• Published: Elsevier 2020-06-01
• Series: EBioMedicine
• Subjects: Breast cancer; Metastatic dissemination; Axillary lymph node; Distant metastasis
• Online Access: http://www.sciencedirect.com/science/article/pii/S2352396420301687

Background: In breast cancer (BC), axillary lymph node (ALN) involvement is one of the strongest adverse prognostic factors. However, it is unclear whether loco-regional lymph node deposits are effectively the root of secondary metastases or only an indicator of competence of the primary tumour to spread to distant organs. Methods: Here, we investigated the evolutionary trajectories of primary tumour, ALN and distant metastasis samples from 16 estrogen-receptor (ER)-positive lymph node-positive BC patients. Low-pass whole genome sequencing was performed to infer somatic copy number aberrations and the phylogenetic profiles for all patients were obtained. Findings: We show that lymph nodes and distant metastases shared a common origin in only 25% of the cases highlighting that the predominant route of metastatic dissemination is the direct seeding of tumour cells from the primary tumour to distant organs, independently of lymph node metastasis. Noticeably, patients sharing a common origin significantly have worse prognosis. Interpretation: Our results shed light on the routes on which tumour cells metastasize and their role in disease progression in ER-positive BC. Funding: This work has received financial support from Les Amis de l'Institut Bordet, MEDIC, the Breast Cancer Research Foundation (BCRF), the Belgian Fonds National de la Recherche Scientifique (F.R.S-FNRS) and from a grant of the Région Wallonne.