Immunohistochemistry (IHC) for MLH1, MSH2, MSH6, and PMS2 protein expression and microsatellite instability (MSI) are well-established tools to screen for Lynch syndrome (LS). Although many cancer ...centers have adopted these tools as reflex LS screening after a colorectal cancer diagnosis, the standard of care has not been established, and no formal studies have described this practice in the United States. The purpose of this study was to describe prevalent practices regarding IHC/MSI reflex testing for LS in the United States and the subsequent follow-up of abnormal results.
A 12-item survey was developed after interdisciplinary expert input. A letter of invitation, survey, and online-survey option were sent to a contact at each cancer program. A modified Dillman strategy was used to maximize the response rate. The sample included 39 National Cancer Institute-designated Comprehensive Cancer Centers (NCI-CCCs), 50 randomly selected American College of Surgeons-accredited Community Hospital Comprehensive Cancer Programs (COMPs), and 50 Community Hospital Cancer Programs (CHCPs).
The overall response rate was 50%. Seventy-one percent of NCI-CCCs, 36% of COMPs, and 15% of CHCPs were conducting reflex IHC/MSI for LS; 48% of the programs used IHC, 14% of the programs used MSI, and 38% of the programs used both IHC and MSI. One program used a presurgical information packet, four programs offered an opt-out option, and none of the programs required written consent.
Although most NCI-CCCs use reflex IHC/MSI to screen for LS, this practice is not well-adopted by community hospitals. These findings may indicate an emerging standard of care and diffusion from NCI-CCC to community cancer programs. Our findings also described an important trend away from requiring written patient consent for screening.
Blood/saliva DNA is thought to represent the germ line in genetic cancer-risk assessment. Cases with pathogenic TP53 variants detected by multigene panel testing are often discordant with Li-Fraumeni ...syndrome, raising concern about misinterpretation of acquired aberrant clonal expansions (ACEs) with TP53 variants as germ-line results.
Pathogenic TP53 variants with abnormal next-generation sequencing metrics (e.g., decreased ratio (<25%) of mutant to wild-type allele, more than two detected alleles) were selected from a CLIA laboratory testing cohort. Alternate tissues and/or close relatives were tested to distinguish between ACE and germ-line status. Clinical data and Li-Fraumeni syndrome testing criteria were examined.
Among 114,630 multigene panel tests and 1,454 TP53 gene-specific analyses, abnormal next-generation sequencing metrics were observed in 20% of 353 TP53-positive results, and ACE was confirmed for 91% of cases with ancillary materials, most of these due to clonal hematopoiesis. Only four met Chompret criteria. Individuals with ACE were older (50 years vs. 33.7; P = 0.02) and were identified more frequently in multigene panel tests (66/285; 23.2%) than in TP53 gene-specific tests (6/68; 8.8%, P = 0.005).
ACE confounds germ-line diagnosis, may portend hematologic malignancy, and may provoke unwarranted clinical interventions. Ancillary testing to confirm germ-line status should precede Li-Fraumeni syndrome management.
Scientific and technologic advances are revolutionizing our approach to genetic cancer risk assessment, cancer screening and prevention, and targeted therapy, fulfilling the promise of personalized ...medicine. In this monograph, we review the evolution of scientific discovery in cancer genetics and genomics, and describe current approaches, benefits, and barriers to the translation of this information to the practice of preventive medicine. Summaries of known hereditary cancer syndromes and highly penetrant genes are provided and contrasted with recently discovered genomic variants associated with modest increases in cancer risk. We describe the scope of knowledge, tools, and expertise required for the translation of complex genetic and genomic test information into clinical practice. The challenges of genomic counseling include the need for genetics and genomics professional education and multidisciplinary team training, the need for evidence-based information regarding the clinical utility of testing for genomic variants, the potential dangers posed by premature marketing of first-generation genomic profiles, and the need for new clinical models to improve access to and responsible communication of complex disease risk information. We conclude that given the experiences and lessons learned in the genetics era, the multidisciplinary model of genetic cancer risk assessment and management will serve as a solid foundation to support the integration of personalized genomic information into the practice of cancer medicine.
As demand for genetic cancer risk assessment (GCRA) continues to increase, so does the sense of urgency to scale up efforts to triage patients, facilitate informed consent, and order genetic testing ...for cancer risk. The National Society of Genetic Counselors outlines the elements of informed consent that should be addressed in a GCRA session. While this practice resource aims to improve health equity, research on how well the elements of informed consent are implemented in practice is lacking. This retrospective and prospective mixed-methods study assessed how adequately the elements of informed consent are addressed during pre-test GCRA among 307 community clinicians (CC) and 129 cancer genetic counselors (GC), and barriers they face to addressing these elements. Results revealed that more than 90% of both cohorts consistently addressed components of at least 5 of the 10 elements of informed consent during a pre-test consultation. Technical aspects and accuracy of the test and utilization of test results were the most similarly addressed elements. Notably, GCs more often review the purpose of the test and who to test, general information about the gene(s), and economic considerations whereas CCs more often review alternatives to testing. Both cohorts reported psychosocial aspects of the informed consent process as the least adequately addressed element. Time constraints and patient-related concerns were most often cited by both cohorts as barriers to optimal facilitation of informed consent. Additional barriers reported by CCs included provider lack of awareness, experience, or education, and availability of resources and institutional support. Findings from this study may contribute to the development of alternative delivery models that incorporate supplementary educational tools to enhance patient understanding about the utility of genetic testing, while helping to mitigate the barrier of time constraints. Equally important is the use of this information to develop continuing education tools for providers.
In germline genetic testing, variants from understudied ancestries have been disproportionately classified as being of uncertain significance. We hypothesized that the rate of variant ...reclassification likewise differs by ancestry.
Nonbenign variants in actionable genes were collected from consenting subjects undergoing genetic testing at two Southern California sites from September 1996 through December 2016. Variant reclassifications were recorded as they were received, until February 2017 or reclassification to benign. Excluding duplicate variants (same ancestry, laboratory, classification), generalized linear models for the hereditary breast cancer genes (BRCA1/2) and other variants investigated whether rate of reclassification differed for seven categories of ancestry compared with non-Hispanic European. Models took into account laboratory, year, gene, sex, and current classification (handled as a time-dependent covariate) and were adjusted for multiple hypothesis testing.
Among 1483 nonbenign variants, 693 (46.7%) involved BRCA1/2. Overall, 268 (18.1%) variants were reclassified at least once. Few (9.7%) reclassified variants underwent a net upgrade in pathogenicity. For BRCA1/2 variants, reclassification rates varied by ancestry and increased over time, more steeply for ancestries with lower initial rates (African, Ashkenazi, Chinese) than for ancestries whose initial rates were high (Middle Eastern) or similar to non-Hispanic European (non-Chinese Asian, Native American, Hispanic). In contrast, reclassification rates of non-BRCA1/2 variants did not vary over time but were elevated for most minority ancestries except non-Chinese Asian and Native American.
For nonbenign variants in cancer-related genes, the rates at which reclassifications are issued vary by ancestry in ways that differ between BRCA1/2 and other genes.
Multigene panels can be a cost- and time-effective alternative to sequentially testing multiple genes, especially with a mixed family cancer phenotype. However, moving beyond our single-gene testing ...paradigm has unveiled many new challenges to the clinician. The purpose of this article is to familiarize the reader with some of the challenges, as well as potential opportunities, of expanded hereditary cancer panel testing.
We include results from 348 commercial multigene panel tests ordered from January 1, 2014, through October 1, 2014, by clinicians associated with the City of Hope's Clinical Cancer Genetics Community of Practice. We also discuss specific challenging cases that arose during this period involving abnormalities in the genes: CDH1, TP53, PMS2, PALB2, CHEK2, NBN, and RAD51C.
If historically high risk genes only were included in the panels (BRCA1, BRCA2, MSH6, PMS2, TP53, APC, CDH1), the results would have been positive only 6.2% of the time, instead of 17%. Results returned with variants of uncertain significance (VUS) 42% of the time.
These figures and cases stress the importance of adequate pre-test counseling in anticipation of higher percentages of positive, VUS, unexpected, and ambiguous test results. Test result ambiguity can be limited by the use of phenotype-specific panels; if found, multiple resources (the literature, reference laboratory, colleagues, national experts, and research efforts) can be accessed to better clarify counseling and management for the patient and family. For pathogenic variants in low and moderate risk genes, empiric risk modeling based on the patient's personal and family history of cancer may supersede gene-specific risk. Commercial laboratory and patient contributions to public databases and research efforts will be needed to better classify variants and reduce clinical ambiguity of multigene panels.
Approximately 12% of the U.S. population is Hispanic, with the majority residing in urban centers such as Los Angeles. The
prevalence of BRCA mutations among high-risk Hispanic families is unknown.
...Methods: One hundred and ten unrelated probands ofHispanicorigin, with a personal or family history of breast and/orovarian
cancer, presented for genetic cancer risk assessment, were enrolled in an Institutional Review Board–approved registry and
underwent BRCA testing. Haplotype analyseswere done if BRCA mutations were observed in two or more unrelated probands.
Results: Mean age at diagnosis was 37 years (range = 23-59) for the 89 (81%) probands with invasive breast cancer. Overall,
34 (30.9%) had deleterious mutations (25 in BRCA1 , 9 in BRCA2 ), 25 (22.7%) had one or more unclassified variants, and 51 (46.4%) had negative results. The mean pretest mutation probability
using the Couch model, Myriad model, and BRCAPro was 19.6% (range = 4-77%). The combined average mutation probability was
32.8% for carriers, 15.5% for noncarriers, and 12.9% for variant carriers ( P < 0.0001). The most common deleterious mutation was 185delAG (4 of 34, 11.8%). The Hispanic 185delAG carrier families share
the same haplotype from D17s1320 through BRCA1 , as do two reference Ashkenazi Jewish families. Haplotype analyses ofadditional recurrent BRCA1 mutations IVS5+1G>A ( n =2),S955X ( n = 3), R1443X ( n = 3), and 2552delC ( n = 2) also suggest founder effects, with four of six mutations seenalmost exclusively in families with Latin American/Caribbean
or Spanish ancestry.
Conclusion: This is the largest study to date of high-risk Hispanic families in the United States. Six recurrent mutations
accounted for 47% (16 of 34) of the deleterious mutations in this cohort. The BRCA1 185delAG mutation wasprevalent (3.6%) in this clinic-based cohort of predominantly Mexican descent, and shared the Ashkenazi
Jewishfounder haplotype.
CONTEXT An autosomal dominant pattern of hereditary breast cancer may be masked by small family size or transmission through males given sex-limited expression. OBJECTIVE To determine if BRCA gene ...mutations are more prevalent among single cases of early onset breast cancer in families with limited vs adequate family structure than would be predicted by currently available probability models. DESIGN, SETTING, AND PARTICIPANTS A total of 1543 women seen at US high-risk clinics for genetic cancer risk assessment and BRCA gene testing were enrolled in a prospective registry study between April 1997 and February 2007. Three hundred six of these women had breast cancer before age 50 years and no first- or second-degree relatives with breast or ovarian cancers. MAIN OUTCOME MEASURE The main outcome measure was whether family structure, assessed from multigenerational pedigrees, predicts BRCA gene mutation status. Limited family structure was defined as fewer than 2 first- or second-degree female relatives surviving beyond age 45 years in either lineage. Family structure effect and mutation probability by the Couch, Myriad, and BRCAPRO models were assessed with stepwise multiple logistic regression. Model sensitivity and specificity were determined and receiver operating characteristic curves were generated. RESULTS Family structure was limited in 153 cases (50%). BRCA gene mutations were detected in 13.7% of participants with limited vs 5.2% with adequate family structure. Family structure was a significant predictor of mutation status (odds ratio, 2.8; 95% confidence interval, 1.19-6.73; P = .02). Although none of the models performed well, receiver operating characteristic analysis indicated that modification of BRCAPRO output by a corrective probability index accounting for family structure was the most accurate BRCA gene mutation status predictor (area under the curve, 0.72; 95% confidence interval, 0.63-0.81; P<.001) for single cases of breast cancer. CONCLUSIONS Family structure can affect the accuracy of mutation probability models. Genetic testing guidelines may need to be more inclusive for single cases of breast cancer when the family structure is limited and probability models need to be recreated using limited family history as an actual variable.
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