Comprehensive Genomic Profiling (CGP)-Informed Personalized Molecular Residual Disease (MRD) Detection: An Exploratory Analysis from the PREDATOR Study of Metastatic Colorectal Cancer (mCRC) Patients Undergoing Surgical Resection.

A majority of patients with metastatic colorectal cancer (mCRC) experience recurrence post curative-intent surgery. The addition of adjuvant chemotherapy has shown to provide limited survival benefits when applied to all patients. Therefore, a biomarker to assess molecular residual disease (MRD) accurately and guide treatment selection is highly desirable for high-risk patients. This feasibility study evaluated the prognostic value of a tissue comprehensive genomic profiling (CGP)-informed, personalized circulating tumor DNA (ctDNA) assay (FoundationOne®Tracker) (Foundation Medicine, Inc., Cambridge, MA, USA) by correlating MRD status with clinical outcomes. ctDNA analysis was performed retrospectively on plasma samples from 69 patients with resected mCRC obtained at the MRD and the follow-up time point. Tissue CGP identified potentially actionable alterations in 54% (37/69) of patients. MRD-positivity was significantly associated with lower disease-free survival (DFS) (HR: 4.97, 95% CI: 2.67−9.24, p < 0.0001) and overall survival (OS) (HR: 27.05, 95% CI: 3.60−203.46, p < 0.0001). Similarly, ctDNA positive status at the follow-up time point correlated with a marked reduction in DFS (HR: 8.78, 95% CI: 3.59−21.49, p < 0.0001) and OS (HR: 20.06, 95% CI: 2.51−160.25, p < 0.0001). The overall sensitivity and specificity at the follow-up time point were 69% and 100%, respectively. Our results indicate that MRD detection using the tissue CGP-informed ctDNA assay is prognostic of survival outcomes in patients with resected mCRC. The concurrent MRD detection and identification of actionable alterations has the potential to guide perioperative clinical decision-making.

Hereditary nonpolyposis colorectal cancer (Lynch Syndrome) in Argentina: report from a referral hospital register.

PURPOSE: The first Argentine experience with epidemiologic, molecular, and genetic counseling data is reported. METHODS: We analyzed 43 families fulfilling Amsterdam criteria identified from a prospective database with data from 779 relatives. RESULTS: Eleven families (25.6 percent) presented as Lynch I, 29 (67.4 percent) as Lynch II, and 3 (7 percent) as Muir-Torre syndrome. Among the 306 affected members, 197 cases of colorectal cancer were identified (mean age at diagnosis, 52.1 (range, 21-90) years). The most frequent extracolonic tumors were gastric adenocarcinoma in males and endometrium adenocarcinoma in females. A high incidence of breast cancer was observed (16 cases among 155 females, crude rate: 11,594.20/100,000). Twenty-seven patients (8.8 percent) developed more than one tumor. These patients were younger than those with only one tumor (45 vs. 51 years; P = 0.001). In 5 of 11 patients who underwent molecular sequencing, a pathologic mutation was found. A novel C deletion at 1910 nucleotide, codon 637, exon 12 of MSH2 gene was identified in a family with a strong aggregation of breast cancer with lack of MSH2 immunohistochemical staining. For 78.2 percent of counseled individuals, this session represented the first time they received information, and 73.9 percent stated that their physicians were unaware of their family background. CONCLUSIONS: Argentine families presented a high incidence of stomach cancer. The elevated incidence of breast cancer and its association with a novel hMSH2 mutation bring to consideration the inclusion of this malignancy as part of the syndrome. A lack of awareness by both physicians and persons at risk was observed.

Adenomatous polyposis families that screen APC mutation-negative by conventional methods are genetically heterogeneous.

PURPOSE: One third of families with classical adenomatous polyposis (FAP), and a majority of those with attenuated FAP (AFAP), remain APC mutation-negative by conventional methods. Our purpose was to clarify the genetic basis of polyposis and genotype-phenotype correlations in such families. PATIENTS AND METHODS: We studied a cohort of 29 adenomatous polyposis families that had screened APC mutation-negative by the protein truncation test, heteroduplex analysis, and exon-specific sequencing. The APC gene was investigated for large genomic rearrangements by multiplex ligation-dependent probe amplification (MLPA), and for allelic mRNA expression by single nucleotide primer extension (SNuPE). The AXIN2 gene was screened for mutations by sequencing. RESULTS: Four families (14%) showed a constitutional deletion of the entire APC gene (three families) or a single exon (one family). Seven families (24%) revealed reduced or extinct mRNA expression from one APC allele in blood, accompanied by loss of heterozygosity in the APC region in six (75%) of eight tumors. In 15 families (52%), possible APC involvement could be neither confirmed nor excluded. Finally, as detailed elsewhere, three families (10%) had germline mutations in genes other than APC, AXIN2 in one family, and MYH in two families. CONCLUSION: "APC mutation-negative" FAP is genetically heterogeneous, and a combination of MLPA and SNuPE is able to link a considerable proportion (38%) to APC. Significant differences were observed in clinical manifestations between subgroups, emphasizing the importance of accurate genetic and clinical characterization for the proper management of such families.

Altered expression of MLH1, MSH2, and MSH6 in predisposition to hereditary nonpolyposis colorectal cancer.

PURPOSE: A considerable fraction (30% to 70%) of families with verified or putative hereditary nonpolyposis colorectal cancer fails to show mutations in DNA mismatch repair (MMR) genes. Our purpose was to address the genetic etiology of such families. MATERIALS AND METHODS: We scrutinized a population-based cohort of 26 families from Finland that had screened mutation-negative by previous techniques. Blood was tested for allelic messenger RNA (mRNA) expression of MLH1, MSH2, and MSH6 by single nucleotide primer extension (SNuPE), and tumor tissue for MMR protein expression by immunohistochemistry (IHC) as well as for microsatellite instability (MSI). Full-length cDNAs of genes implicated by SNuPE or IHC were cloned and sequenced. RESULTS: Unbalanced mRNA expression of MLH1 alleles was evident in two families. An inherited nonsense mutation was subsequently identified in one family, and complete silencing of the mutated allele was identified in the other family. Extinct protein expression by IHC implicated MLH1 in these two and in four other families, MSH2 in four families, and MSH6 in one family. Although no unequivocal genomic mutations were detected in the latter families, haplotype and other findings provided support for heritable defects. With one exception, all tumors with IHC alterations showed MSI, in contrast to the remaining families, which showed neither IHC changes nor MSI. CONCLUSION: Our expression-based strategy stratified the present "mutation-negative" cohort into two discrete categories: families linked to the major MMR genes MLH1, MSH2, and MSH6 (11 [42%] of 26) and those likely to be associated with other, as yet unknown susceptibility genes (15 [58%] of 26).