Value of Immunocytochemistry for the Detection of the BRAFV600E Mutation in Circulating Tumor Cells from Metastatic Melanoma Patients
Veronique Hofman, Marius Ilie, Elodie Long-Mira, Damien Giacchero, Catherine Butori, Berengere Dadone, Eric Selva, Virginie Gavric-Tanga, Thierry Passeron, Gilles Poissonnet, Jean-Francois Emile, Jean-Philippe Lacour, Philippe Bahadoran, Paul Hofman. Pasteur Hospital, Nice, France; Archet Hospital, Nice, France; Antoine Lacassagne Centre, Nice, France; Ambroise Paré Hospital, Boulogne, France
Background: Therapies targeting the BRAFV600E mutation have transformed the treatment of patients with advanced melanoma. While the BRAFV600E mutation is usually detected in melanoma tissue samples, detection in circulating tumor cells (CTCs) would allow non-invasive stratification of patients and examination of the effect of targeted therapies.
Design: We aimed to detect BRAFV600E by immunocytochemistry (ICC) in CTCs isolated using the isolation by size of epithelial tumor cells (ISET) technology. Formalin fixed tumor tissues from 98 metastatic melanoma patients were screened for BRAFV600E both by pyrosequencing, using the Therascreen BRAF kit, and by immunohistochemistry, using the VE1 antibody. Concomitantly and blindly, ICC for the BRAF mutation was performed on CTCs isolated by ISET.
Results: 53/98 (54%) patients had the BRAFV600E mutation when detected by pyrosequencing in tumor tissue. Among these patients, 51/53 (96%) showed tissue immunostaining with the VE1 antibody. 87/98 (89%) patients demonstrated CTCs, of which 54/87 (62%) harbored BRAFV600E detected by ICC. 46/54 (85%) of ICC-CTC positive patients had BRAFV600E positive tumors and 8/54 (15%) of them showed BRAFV600E negative tumors as demonstrated by sequencing.
Conclusions: These results show that CTCs are frequently found in patients with advanced melanoma when using ISET. Detection of BRAFV600E by ICC was highly sensitive and reliable.
Tuesday, March 5, 2013 9:30 AM
Poster Session III # 38, Tuesday Morning