O-018 Clinical application of targeted next generation sequencing for colorectal cancer patients: a multicentric Belgian experience

Abstract

Introduction: Colorectal Cancer is the second most frequent cancer in Europe irrespective of gender and is still yielding a high mortality rate. Despite broad screening program, 25% of the patients are metastatic at initial diagnosis. Promising targeted therapy and personalized medicine are making molecular profiling of tumours a priority. International efforts to catalogue mutations for multiple forms of cancer coupled with the successes of targeted agents in patients with molecularly defined tumors have generated enthusiasm for incorporating genomic profiling into clinical cancer practice. American and European guidelines are clearly emphasizing expanded RAS (KRAS and NRAS) status as a mandatory precondition for use of anti-EGFR therapy. Indeed, not only the benefit of anti-EGFR therapy is confined to RAS wild type (wt) tumours, but treatment with anti-EGFR antibodies may even harm patients with a RAS mutation. BRAF mutation is a strong negative prognostic biomarkers and evidence is accumulating that patients with a BRAF mutant tumour do not benefit from anti-EGFR therapy. Daily emerging new data on theranostic and prognostic role of molecular biomarkers are a strong incentive for a validated, sensitive and broadly available molecular screening test in order to implement and improve multi-modal therapy strategy and clinical trials. Recently, next generation sequencing (NGS) has begun to supplant other technologies for genomic profiling that is now important for targeted therapies. In the present study, our goal is to share a successful 3 years-old clinical experience using NGS results to help therapeutic decisions. Methods: The Ion Torrent AmpliSeq colon/lung cancer panel which allows mutations detection in 22 cancer-related genes was prospectively used in clinical practice (BELAC ISO 15189 accredited method). The DNA of 750 colorectal tumours, including primary tumours and metastasis, from 11 different institutions was obtained from formalin fixed paraffin embedded material and subjected to targeted NGS using the Ion Torrent Personal Genome Machine. Results: Among the 750 tumours tested, 735 (98%) were successfully sequenced. The number of mutations per tumour ranged from 0 to 5 and 655 (89.1%) of the sequenced samples were harboring at least one mutation. 337 samples (45,8%) were KRAS mutant, with exon 2 mutation being the most common one (84%). 32 samples (4,3%) were positive for a NRAS mutation and 79 (10,7%) were BRAF mutant. The frequencies of these variants detected by NGS were consistent with frequencies reported in public databases. Moreover mutations and amplification in potentially actionable genes were identified in 161 samples (21.9%) including 100 PIK3CA mutations (13.6%), 40 FBXW7 mutations (5.4%), 10 PTEN mutations (1.4%), 4 ERBB2 mutations (0.5%), 2 ERBB2 amplifications (0.3%) confirmed by FISH, 4 AKT1 mutations (0.5%) and 1 MAP2K1 mutation (0.1%). The median turnaround time between the reception of the sample in the laboratory and report release was 8 calendar days. Conclusion: Overall, the AmpliSeq colon/lung cancer panel can be applied in daily practice and provide reliable clinically relevant information for colorectal cancer patients.