Detection of Cancer DNA in Plasma of Early Stage Breast Cancer Patients
Menée sur des échantillons tumoraux prélevés sur 29 patientes atteintes d'un cancer du sein de stade précoce et sur des échantillons de sang prélevés avant et après l'opération chirurgicale, cette étude évalue les performances d'une technologie à base de PCR numérique pour détecter, dans l'ADN tumoral circulant, des mutations de gènes susceptibles de guider le choix thérapeutique
Purpose: Detecting circulating plasma tumor DNA (ptDNA) in early stage cancer patients has the potential to change how oncologists recommend systemic therapies for solid tumors after surgery. Droplet digital polymerase chain reaction (ddPCR) is a novel sensitive and specific platform for mutation detection.
Experimental Design: In this prospective study, primary breast tumors and matched pre- and post-surgery blood samples were collected from early stage breast cancer patients (n=29). Tumors (n=30) were analyzed by Sanger sequencing for common PIK3CA mutations, and DNA from these tumors and matched plasma were then analyzed for PIK3CA mutations using ddPCR.
Results: Sequencing of tumors identified seven PIK3CA exon 20 mutations (H1047R) and three exon 9 mutations (E545K). Analysis of tumors by ddPCR confirmed these mutations and identified five additional mutations. Pre-surgery plasma samples (n=29) were then analyzed for PIK3CA mutations using ddPCR. Of the fifteen PIK3CA mutations detected in tumors by ddPCR, fourteen of the corresponding mutations were detected in pre-surgical ptDNA, while no mutations were found in plasma from patients with PIK3CA wild type tumors (sensitivity 93.3%, specificity 100%). Ten patients with mutation positive ptDNA pre-surgery had ddPCR analysis of post-surgery plasma, with five patients having detectable ptDNA post-surgery.
Conclusions: This prospective study demonstrates accurate mutation detection in tumor tissues using ddPCR, and that ptDNA can be detected in blood before and after surgery in early stage breast cancer patients. Future studies can now address whether ptDNA detected after surgery identifies patients at risk for recurrence, which could guide chemotherapy decisions for individual patients.
Clinical Cancer Research , résumé, 2014