Rare germline variants in the AXIN2 gene in families with colonic polyposis and colorectal cancer.

Germline loss-of-function variants in AXIN2 are associated with oligodontia and ectodermal dysplasia. The association between colorectal cancer (CRC) and colonic polyposis is less clear despite this gene now being included in multi-gene panels for CRC. Study participants were people with genetically unexplained colonic polyposis recruited to the Genetics of Colonic Polyposis Study who had a rare germline AXIN2 gene variant identified from either clinical multi-gene panel testing (n=2) or from whole genome/exome sequencing (n=2). Variant segregation in relatives and characterisation of tumour tissue were performed where possible. Four different germline pathogenic variants in AXIN2 were identified in four families. Five of the seven carriers of the c.1049delC, p.Pro350Leufs*13 variant, two of the six carriers of the c.1994dupG, p.Asn666Glnfs*41 variant, all three carriers of c.1972delA, p.Ser658Alafs*31 variant and the single proband carrier of the c.2405G>C, p.Arg802Thr variant, which creates an alternate splice form resulting in a frameshift mutation (p.Glu763Ilefs*42), were affected by CRC and/or polyposis. Carriers had a mean age at diagnosis of CRC/polyposis of 52.5 ± 9.2 years. Colonic polyps were typically pan colonic with counts ranging from 5 to >100 (median 12.5) comprising predominantly adenomatous polyps but also serrated polyps. Two CRCs from carriers displayed evidence of a second hit via loss of heterozygosity. Oligodontia was observed in carriers from two families. Germline AXIN2 pathogenic variants from four families were associated with CRC and/or polyposis in multiple family members. These findings support the inclusion of AXIN2 in CRC and polyposis multigene panels for clinical testing.

Mainstream genetic testing for breast cancer patients: early experiences from the Parkville Familial Cancer Centre.

The demand for genetic testing of hereditary breast cancer genes such as BRCA1 and BRCA2 has continued to increase with the lowering costs of testing, raised awareness in the general public, and implications for breast cancer treatment when a patient is identified as having a germline pathogenic variant. Historically within Australia, patients affected by high genetic risk breast cancers have been referred to a familial cancer centre (FCC) for assessment and testing, resulting in wait times for an appointment for pre- and post-test genetic counselling and an increased demand on the public-funded FCC. To improve patient access and pace of genetic testing, as well as refocus FCC resources, a mainstream clinical genetic testing program was rolled out in September 2017 through the Parkville FCC (PFCC) in Australia at 10 hospital sites. This program enables specialist doctors of eligible patients affected by breast cancer to arrange genetic testing directly at an oncology/surgical appointment and follow up the results as part of the patients' routine clinical care. In this model, the specialist doctor is responsible for any treatment implications of the genetic test result, and the PFCC is responsible for result interpretation, future cancer risk, family cascade testing and segregation testing where warranted. To date the program has had successful uptake, a notable pathogenic variant detection rate, reduced the burden on the PFCC enabling a reallocation of resources and has streamlined the process of genetic testing for eligible patients. Investigation into the patient and clinician experiences of the mainstream program is required.

"It wasn't just for me": Motivations and implications of genetic testing for women at a low risk of hereditary breast and ovarian cancer syndrome.

OBJECTIVE: Genetic testing for hereditary breast and ovarian cancer (HBOC) due to pathogenic variants in BRCA1 or BRCA2 is why most women present to familial cancer centers. Despite being assessed as low risk for HBOC, many women proceed with genetic testing. This study explored the genetic testing experiences of unaffected women at low risk of HBOC to clarify what motivates these women to have testing, and what are the implications of the results. METHODS: A qualitative approach was taken. Participants included women who had genetic testing for HBOC from 2016-2018 at the Parkville Familial Cancer Centre in Melbourne, Australia. In-depth, semi-structured interviews were conducted, and thematic analysis was undertaken on transcripts; transcripts were coded, codes were organized into a hierarchical system of categories/subcategories, and key themes were identified. RESULTS: Analysis of 19 transcripts identified five themes: family underpinned all motivators for HBOC genetic testing; health professionals were influential throughout the process; participants were planning for a positive result; results influenced screening-anxiety and frequency; and negative results gave participants relief in many different ways. The three participants with positive results reported feeling shocked at the results and empowered giving this information to family members. CONCLUSIONS: Women at low HBOC risk may be motivated to seek genetic testing, and access to this is increasingly offered through non-genetic health professionals. Professionals can support clients through genetic testing by recognizing familial experiences, providing accurate information, addressing risk perceptions, and understanding cancer anxiety felt by many women.

Phenotypic confirmation of oligodontia, colorectal polyposis and cancer in a family carrying an exon 7 nonsense variant in the AXIN2 gene.

The AXIN2 gene, like APC, plays a role in the Wnt signalling pathway involved in colorectal tumour formation. Heterozygous mutations in AXIN2 have been shown to cause ectodermal dysplasia (including tooth agenesis, or more specifically, oligodontia), and, in some carriers, colorectal cancer and/or adenomatous polyposis develops. There is a paucity of published AXIN2 families making genotype-phenotype (polyposis, colorectal cancer and oligodontia) correlations challenging. In this case report we describe a family with c.1972delA, p.Ser658Alafs*31 nonsense variant in AXIN2 where the three confirmed carriers presented with both oligodontia and colorectal adenomatous polyposis; mean number of teeth missing in carriers was 16.5 (range 11-22) and mean number of polyps in carriers was 49 (range 5->100, polyps were predominantly adenomatous). This highlights the importance of confirming phenotypic information in familial polyposis, to guide appropriate genetic investigations, as well as providing additional phenotypic and penetrance data to aid in clinical risk management recommendations. Our experience supports the inclusion of AXIN2 on panels for testing of patients with polyposis.

"I'm Healthy, It's Not Going To Be Me": Exploring experiences of carriers identified through a population reproductive genetic carrier screening panel in Australia.

Advancing genetic testing technologies mean that population-based carrier screening for multiple inherited conditions is now available. As the number of genetic conditions being screened increases, there is a need for research into how people experience these screening programs. This research aimed to explore how women experience simultaneous carrier screening for three inherited conditions: cystic fibrosis (CF), spinal muscular atrophy (SMA), and fragile X syndrome (FXS). A qualitative approach was adopted using in-depth semi-structured interviews to explore the experiences of ten female participants: five SMA carriers, three CF carriers, and two FXS premutation carriers. Eight participants were pregnant when offered screening by their general practitioner or obstetrician and the decision to have screening was described as straightforward. Participants reported experiencing emotional responses such as anxiety and stress while waiting for either their partner's carrier screen result (CF or SMA carriers) or the pregnancy's CVS result (FXS carrier) and sought additional information about the relevant condition during this time. Most participants were in favor of population carrier screening for these conditions, preferably prior to conception. Genetic counselors played an essential role in supporting couples after they received a carrier result given the variable consent processes undertaken when screening was offered. Further research should focus on the development of reliable online information tailored to people receiving carrier results and strategies for raising awareness of the availability of population carrier screening within the community. © 2016 Wiley Periodicals, Inc.