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F. Grosso

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    O22 - Mesothelioma III (ID 122)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Mesothelioma
    • Presentations: 1
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      O22.01 - Next generation sequencing in malignant pleural mesothelioma: preliminary data from a retrospective cohort of 123 patients (ID 2290)

      16:15 - 17:45  |  Author(s): F. Grosso

      • Abstract
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      The median survival of patients with advanced stage malignant pleural mesothelioma (MPM) ranges between 9 and 12 months after diagnosis, regardless of the recent achievements with systemic therapies combining cisplatin and antifolates such as pemetrexed or raltitrexed. Since MPM is a relatively rare malignancy and early pre-neoplastic lesions are clinically difficult to be identified, the understanding of molecular pathogenesis including sequential accumulation of genetic/epigenetic alterations for MPM development has lagged behind other common malignancies. According to the COSMIC database the most frequently mutated genes in MPM include CDKN2A, NF2 and BAP1, followed by other 12 genes having been found mutated in a fraction of MPM cases (c-MET, VHL,WT1 among others). Clearly, a better and more systematic understanding of the role of genomic alterations in MPM is needed. In this retrospective study, a consecutive series of 123 formalin-fixed, paraffin embedded (FFPE) MPM tissue samples with clinical annotates, collected at two institutions, was retrospectively analyzed through Next-Generation Sequencing (NGS) technology to enhance knowledge about tumor-specific genomic profiling.

      Genomic DNA was extracted by tumour microdissected FFPE samples for all 123 patients. Amplicons NGS libraries for 50 Oncogene included in Ion AmpliSeq™ Cancer Hotspot Panel (CHP) v.2 were generated as indicated by manufacturer, and sequenced in Personal Genome Machine IonTorrent. Variant Caller included in Torrent Suite Software was utilised to identify mutations in the samples, annotation was performed with Annovar software. Genomic analysis for BAP1 and NF2 (not included in the CHP) is separately ongoing.

      Of 123 advanced stage MPM patients, all treated with pemetrexed-based chemotherapy, 70% were males, current smokers 50%, median age 66.5 (range 36-82) years and histological subtypes were 96/22/5 epithelioid/biphasic/sarcomatous. With a cut off for allele frequency(AF)>=10% a total of 966 non-synonymous, 8 del-ins, 62 nonsense, 637 intronic, 204 regulatory and 1140 synonymous somatic sequence variations were detected in 107 patients already screened. Excluding synonymous mutations and irrespective of AF, the five most frequently altered genes were CSF1R (mut:154, pts:80), KDR (mut:148, pts:73), FLT3 (mut:132, pts:99), PIK3CA (mut:126, pts:60), TP53 (mut:111, pts:66). Evaluating mutations identified at least once, a correlation between HRAS and PIK3CA mutations and patient status (dead or alive) was observed (p=0.017 and p=0.039, respectively). Specifically, HRAS silent mutation p.H27H (rs12628) was responsible for the association (p=0.021) and occurred in 54% of 107 MPM compared to 30% of reported AF in available databases. PIK3CA p.I391M missense mutation (rs2230461; AF 24% in this series) was significantly associated to progression-disease (p=0.003). Among the other SNPs reported in at least 15 pts there are rs3729674(PIK3CA), rs1800863(RET), rs3822214(KIT), rs10006115(KDR), rs75580865(FLT3) and rs5030613(SMARCB1).

      These extremely preliminary data indicate that NGS technology is feasible in FFPE MPM tissues and some of the detected genetic mutations are novel observations of potential prognostic and therapeutic interest.

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