Exploring the impact of BRCA1 and BRCA2 mutation type and location on Olaparib maintenance therapy in platinum-sensitive relapsed ovarian Cancer patients: A single center report.

OBJECTIVE: In patients with platinum-sensitive relapsed ovarian cancer (PSROC) harboring pathogenic/likely pathogenic variants (PV) in BRCA1 and BRCA2 genes, olaparib maintenance monotherapy (OMT) is a viable option. Our study aimed to evaluate the impact of different BRCA1/2 PV in survival outcomes and safety of OMT in BRCA1/2-mutated PSROC patients, focusing on the type and location of PV. METHODS: We assessed the outcomes of 100 BRCA1/2-mutated PSROC patients treated at our institute, analyzing progression-free survival (PFS) and overall survival (OS). Germline and tumor BRCA1/2 genotyping was conducted using Illumina's next-generation sequencing (NGS). RESULTS: PFS and OS were significantly shorter in PSROC patients with PV in BRCA1 compared to those with PV in BRCA2 (PFS:14.0 vs. 38.8 months, p = 0.007, OS: 21.8 vs. 62.0 months, p = 0.011). Notably, there was a significant difference in PFS based on the intragenic location of BRCA1 PV, with shorter PFS in patients with 1st/2nd relapse, harboring PV in BRCA1 RING domain compared to those with PV in the DNA binding domain (DBD) and BRCT domains (12.4 vs. 23.0 months, p = 0.046). No differences in PFS and OS were observed between patients with germline versus somatic BRCA1/2 PV (PFS:14.9 vs.19.3, p = 0.316, OS: not reached vs. 25.8 months; p = 0.224). However, there were significant differences in the reasons for OMT discontinuation between patients with germline and somatic BRCA1/2 PV, primarily due to adverse side effects. CONCLUSIONS: In summary, the type and location of BRCA1 and BRCA2 PV provide additional insight into the expected survival outcomes of olaparib MT in PSROC patients. TRIAL REGISTRATION NUMBER: ISRCTN42408038, Name of registry: ISRCTN registry, Date of registration: 24/11/2015.

Correlation of treatment outcome in sanger/RT­qPCR KIT/PDGFRA wild­type metastatic gastrointestinal stromal tumors with next­generation sequencing results: A single­center report.

In patients with gastrointestinal stromal tumors (GIST), it has become mandatory to determine the driver mutation in order to predict the response to standard treatment with tyrosine kinase inhibitors (TKI). A total of 10­15% of all GIST lack activating mutations in KIT proto­oncogene, receptor tyrosine kinase (KIT)/platelet­derived growth factor receptor alpha (PDGFRA) and have been classified as KIT/PDGFRA wild­type (WT) GIST. They are characterized by poor response to TKI. From a group of 119 metastatic GIST patients, 17 patients with KIT/PDGFRA/BRAF WT GIST as determined by reverse transcription­quantitative (RT­q) PCR and Sanger sequencing were profiled by a targeted next­generation sequencing (NGS) approach and their treatment outcome was assessed. In the present study, 41.2% of patients as KIT/PDGFRA/BRAF WT GIST examined with RT­qPCR and Sanger sequencing were confirmed to be carriers of pathogenic KIT/PDGFRA mutations by NGS and were responsive to TKI. The percentage of genuinely KIT/PDGFRA WT GIST in the present study thereby dropped from the initial 14.3% detected with the RT­qPCR and Sanger sequencing to 7.6% after NGS. Their outcome was universally poor. The reliability of RT­qPCR and direct Sanger sequencing results in this setting is therefore insufficient and it is recommended that NGS becomes a requirement for treatment decision at least in KIT/PDGFRA/BRAF WT GIST as determined by RT­qPCR and Sanger sequencing.

Mutational spectrum and classification of novel mutations in patients with metastatic gastrointestinal stromal tumours.

In total, ~85% of malignant gastrointestinal stromal tumours (GISTs) harbour activating mutations in one of the genes KIT or PDGFRA, while 10­15% of all GISTs have no detectable KIT or PDGFRA mutations, but could have alterations in genes of the succinate dehydrogenase complex or in BRAF, PIK3CA or rarely RAS family genes. The clinical benefit of tyrosine kinase inhibitors, such as imatinib, depends on the GIST genotype, therefore molecular characterization of GIST has a crucial role in overall management of GIST. The aim of the present study was to molecularly characterize a cohort of 70 patients with metastatic GISTs from the Slovenian Cancer Registry (National Cancer Registry) treated between January 2002 and December 2011. Exons 9, 11, 13 and 17 of the KIT gene and exons 12, 14 and 18 of the PDGFRA gene were analysed by direct Sanger sequencing. All KIT/PDGFRA wild­type GISTs were tested for the presence of mutations in hot spot regions of KRAS, NRAS, BRAF, PIK3CA and AKT1 genes. Novel variants were characterized and classified using Cancer Genome Interpreter and according to The American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines. In total, 60 (85.7%) patients had mutations in KIT and 2 (2.9%) in PDGFRA. Whereas, 8 (11.4%) patients with GIST had no mutation in either of the analysed genes. The majority of GIST cases (n=52) had a mutation in KIT exon 11, where 40 different mutations were detected. Eight of the variants were novel: c.1652_1672del, c.1653_1660delinsAA, c.1665_1672delinsCC, c.1668_1686del, c.1676_1720del, c.1715_1756dup, c.1721_1765dup, and c.1722_1766dup. Mutation frequencies of KIT and PDGFRA genes observed in Slovenian patients are comparable with those in other European populations. In the present group of patients analysed, the most frequently mutated region was exon 11 in the KIT gene, responsible for coding juxtamembrane domain of KIT protein. In this region, eight novel mutations were identified and classified as likely pathogenic driver variants. In addition, the present study identified 6 patients with secondary KIT mutation and 1 patient with double mutant GIST, who had two different mutations in PDGFRA exon 14.