A54: A clinical correlation study of ALK-rearranged circulating tumour cell subsets under crizotinib therapy – to assess for their potential role as predictive biomarkers in non-small-cell lung carcinoma
1University of Paris-Sud, Gustave Roussy, Paris, France,2Translational Research Laboratory, Gustave Roussy, Paris, France,3Department of Biopathology, Gustave Roussy, Paris, France,4Department of Pathology, Gustave Roussy, Paris, France,5Department of Biostatistics and Epidemiology, Gustave Roussy, Paris, France,6Department of Medicine, Gustave Roussy, Paris, France
The success of molecular-targeted therapies heralded a new paradigm in the treatment of non-small-cell lung cancer (NSCLC.) ALK-inhibitors have demonstrated impressive clinical results in the 2-7% of NSCLC patients harbouring ALK-rearrangements. Patients however, universally develop resistance with a variable duration of treatment response. ALK-rearrangement detection is difficult in tumour biopsies; we previously reported ALK-rearrangement detection in circulating tumour cells (CTCs) using filter-adapted FISH (FA-FISH). During this study we noted the presence of CTC subsets with specific ALK-FISH patterns. These subsets demonstrated highly variable evolution under crizotinib therapy suggesting the possibility of subpopulations harbouring differing sensitivities to treatment. Our objective is to analyse whether ALK-rearranged CTC subsets monitored under crizotinib therapy and categorized according to FISH analysis, correlate with clinical parameters such as progression-free survival and thus predict those patients who are at risk of early resistance.
The patient cohort consists of 40 patients at Gustave Roussy with NSCLC and ALK-rearrangement present in both tumour biopsy and CTCs. Blood samples were collected at baseline prior to commencing crizotinib and 2-3 months after. ALK-rearrangement in CTCs was detected using: immunofluorescence staining (CD45/DAPI); to exclude WBCs from analysis and FA-FISH after Isolation by Size of Epithelial Tumour Cells (ISET) filtration. ALK-rearranged subsets were categorised according to the number of FISH break-apart signals and native copies. Clinical data was collected retrospectively from the institutes electronic clinical database.
ALK-FISH analysis has been performed in 40 patients at baseline and 30 at 2-3 months under crizotinib therapy. Three ISET spots have been analysed per sample (equating to 3ml of blood) and FA-FISH results validated by a cytogenetician. Statistical analysis for clinical correlation is ongoing; the results will be presented at the conference.
We expect that this correlation study will help to categorise ALK-rearranged CTC subsets and identify which may be predictive of sensitivity to crizotinib therapy.