A decade of RAD51C and RAD51D germline variants in cancer.

Defects in DNA repair genes have been extensively associated with cancer susceptibility. Germline pathogenic variants (GPV) in genes involved in homologous recombination repair pathways predispose to cancers arising mainly in the breast and ovary, but also other tissues. The RAD51 paralogs RAD51C and RAD51D were included in this group 10 years ago when germline variants were associated with non-BRCA1/2 familial ovarian cancer. Here, we have reviewed the landscape of RAD51C and RAD51D germline variants in cancer reported in the literature during the last decade, integrating this list with variants identified by in-house patient screening. A comprehensive catalog of 341 variants that have been classified applying ACMG/AMP criteria has been generated pinpointing the existence of recurrent variants in both genes. Recurrent variants have been extensively discussed compiling data on population frequencies and functional characterization if available, highlighting variants that have not been fully characterized yet to properly establish their pathogenicity. Finally, we have complemented this data with relevant information regarding the conservation of mutated residues among RAD51 paralogs and modeling of putative hotspot areas, which contributes to generating an exhaustive update on these two cancer predisposition genes.

Meaningful relationships as a driving force in the experience of parents of a child living with polyposis conditions.

While much research has been conducted on the experiences of individuals with inflammatory bowel diseases, there remains a dearth of research conducted on those affected by polyposis conditions. As a result, little is known about the lived experiences of those with polyposis conditions, especially in the cases of parents of pediatric patients with these conditions. Using a hermeneutical phenomenological qualitative research approach, this study sought to explore the lived experiences of parents of children with polyposis conditions, with specific attention paid to the processes in which parents engage in order to adapt to their realities. In total, three major themes were revealed from the experiences of seven participants. Parents discussed the importance of building collaborative relationships with family physicians, building reassuring relationships with other parents, and building educative relationships with their child. These findings demonstrate the need for family-centered care practices by physicians, and role of relevant relationships as a driving force in helping parents in the management of their child's illness.

Evolution of genetic assessment for BRCA-associated gynaecologic malignancies: a Canadian multisociety roadmap.

The landscape of genetic testing in ovarian cancer patients has changed dramatically in recent years. The therapeutic benefits of poly ADP-ribose polymerase (PARP) inhibitors in treatment of BRCA1/2-related ovarian cancers has resulted in an increased demand and urgency for genetic testing results, while technological developments have led to widespread use of multi-gene cancer panels and development of tumour testing protocols. Traditional genetic counselling models are no longer sustainable and must evolve to match the rapid evolution of genetic testing technologies and developments in personalized medicine. Recently, representatives from oncology, clinical genetics, molecular genetics, pathology, and patient advocacy came together to create a national multi-disciplinary Canadian consortium. By aligning stakeholder interests, the BRCA Testing to Treatment (BRCA TtoT) Community of Practice aims to develop a national strategy for tumour and germline BRCA1/2 testing and genetic counselling in women with ovarian cancer. This article serves to provide an overview of the recent evolution of genetic assessment for BRCA1/2-associated gynecologic malignancies and outline a Canadian roadmap to facilitate change, improve genetic testing rates, and ultimately improve outcomes for hereditary ovarian cancer patients and their families.

Broad spectrum of neuropsychiatric phenotypes associated with white matter disease in PTEN hamartoma tumor syndrome.

White matter lesions have been described in patients with PTEN hamartoma tumor syndrome (PHTS). How these lesions correlate with the neurocognitive features associated with PTEN mutations, such as autism spectrum disorder (ASD) or developmental delay, has not been well established. We report nine patients with PTEN mutations and white matter changes on brain magnetic resonance imaging (MRI), eight of whom were referred for reasons other than developmental delay or ASD. Their clinical presentations ranged from asymptomatic macrocephaly with normal development/intellect, to obsessive compulsive disorder, and debilitating neurological disease. To our knowledge, this report constitutes the first detailed description of PTEN-related white matter changes in adult patients and in children with normal development and intelligence. We present a detailed assessment of the neuropsychological phenotype of our patients and discuss the relationship between the wide array of neuropsychiatric features and observed white matter findings in the context of these individuals.

Breast-cancer risk in families with mutations in PALB2.

BACKGROUND: Germline loss-of-function mutations in PALB2 are known to confer a predisposition to breast cancer. However, the lifetime risk of breast cancer that is conferred by such mutations remains unknown. METHODS: We analyzed the risk of breast cancer among 362 members of 154 families who had deleterious truncating, splice, or deletion mutations in PALB2. The age-specific breast-cancer risk for mutation carriers was estimated with the use of a modified segregation-analysis approach that allowed for the effects of PALB2 genotype and residual familial aggregation. RESULTS: The risk of breast cancer for female PALB2 mutation carriers, as compared with the general population, was eight to nine times as high among those younger than 40 years of age, six to eight times as high among those 40 to 60 years of age, and five times as high among those older than 60 years of age. The estimated cumulative risk of breast cancer among female mutation carriers was 14% (95% confidence interval [CI], 9 to 20) by 50 years of age and 35% (95% CI, 26 to 46) by 70 years of age. Breast-cancer risk was also significantly influenced by birth cohort (P<0.001) and by other familial factors (P=0.04). The absolute breast-cancer risk for PALB2 female mutation carriers by 70 years of age ranged from 33% (95% CI, 25 to 44) for those with no family history of breast cancer to 58% (95% CI, 50 to 66) for those with two or more first-degree relatives with breast cancer at 50 years of age. CONCLUSIONS: Loss-of-function mutations in PALB2 are an important cause of hereditary breast cancer, with respect both to the frequency of cancer-predisposing mutations and to the risk associated with them. Our data suggest the breast-cancer risk for PALB2 mutation carriers may overlap with that for BRCA2 mutation carriers. (Funded by the European Research Council and others.).

Disruption of the ASTN2/TRIM32 locus at 9q33.1 is a risk factor in males for autism spectrum disorders, ADHD and other neurodevelopmental phenotypes.

Rare copy number variants (CNVs) disrupting ASTN2 or both ASTN2 and TRIM32 have been reported at 9q33.1 by genome-wide studies in a few individuals with neurodevelopmental disorders (NDDs). The vertebrate-specific astrotactins, ASTN2 and its paralog ASTN1, have key roles in glial-guided neuronal migration during brain development. To determine the prevalence of astrotactin mutations and delineate their associated phenotypic spectrum, we screened ASTN2/TRIM32 and ASTN1 (1q25.2) for exonic CNVs in clinical microarray data from 89 985 individuals across 10 sites, including 64 114 NDD subjects. In this clinical dataset, we identified 46 deletions and 12 duplications affecting ASTN2. Deletions of ASTN1 were much rarer. Deletions near the 3' terminus of ASTN2, which would disrupt all transcript isoforms (a subset of these deletions also included TRIM32), were significantly enriched in the NDD subjects (P = 0.002) compared with 44 085 population-based controls. Frequent phenotypes observed in individuals with such deletions include autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), speech delay, anxiety and obsessive compulsive disorder (OCD). The 3'-terminal ASTN2 deletions were significantly enriched compared with controls in males with NDDs, but not in females. Upon quantifying ASTN2 human brain RNA, we observed shorter isoforms expressed from an alternative transcription start site of recent evolutionary origin near the 3' end. Spatiotemporal expression profiling in the human brain revealed consistently high ASTN1 expression while ASTN2 expression peaked in the early embryonic neocortex and postnatal cerebellar cortex. Our findings shed new light on the role of the astrotactins in psychopathology and their interplay in human neurodevelopment.

Multigene panels in prostate cancer risk assessment: a systematic review.

PURPOSE: Single-nucleotide polymorphism (SNP) panel tests have been proposed for use in the detection of, and prediction of risk for, prostate cancer and as prognostic indicator in affected men. A systematic review was undertaken to address three research questions to evaluate the analytic validity, clinical validity, clinical utility, and prognostic validity of SNP-based panels. METHODS: Data sources comprised MEDLINE, Cochrane CENTRAL, Cochrane Database of Systematic Reviews, and EMBASE; these were searched from inception to April 2013. The gray-literature searches included contact with manufacturers. Eligible studies included English-language studies evaluating commercially available SNP panels. Study selection and risk of bias assessment were undertaken by two independent reviewers. RESULTS: Twenty-one studies met eligibility criteria. All focused on clinical validity and evaluated 18 individual panels with 2 to 35 SNPs. All had poor discriminative ability (overall area under receiver-operator characteristic curves, 58-74%; incremental gain resulting from inclusion of SNP data, 2.5-11%) for predicting risk of prostate cancer and/or distinguishing between aggressive and asymptomatic/latent disease. The risk of bias of the studies, as assessed by the Newcastle Ottawa Scale (NOS) and Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tools, was moderate. CONCLUSION: The evidence on currently available SNP panels is insufficient to assess analytic validity, and at best the panels assessed would add a small and clinically unimportant improvement to factors such as age and family history in risk stratification (clinical validity). No evidence on the clinical utility of current panels is available.Genet Med 18 6, 535-544.

Mutation analysis of PALB2 in BRCA1 and BRCA2-negative breast and/or ovarian cancer families from Eastern Ontario, Canada.

BACKGROUND: PALB2 has emerged as a breast cancer susceptibility gene. Mutations in PALB2 have been identified in almost all breast cancer populations studied to date, but the rarity of these mutations and lack of information regarding their penetrance makes genetic counseling for these families challenging. We studied BRCA1/2 -negative breast and/or ovarian cancer families to a) assess the contribution of PALB2 mutations in this series and b) identify clinical, pathological and family history characteristics that might make PALB2 screening more efficient. METHODS: The coding region of the PALB2 gene was analyzed in 175 probands with family histories of breast and/or ovarian cancer ascertained from a single Canadian institution in Eastern Ontario. RESULTS: We identified 2 probands with PALB2 mutations that are known or strongly considered to be pathogenic and 3 probands with missense mutations that are possibly pathogenic. One of the identified truncating mutations [c.3113G > A (p.Gly1000_Trp1038del - major product)], has been previously described while the other four mutations [c.3507_3508delTC (p.H1170Ffs*19), c.1846G > C (p.D616H), c.3418 T > G (p.W1140G), c.3287A > G (p.N1096S)] have not been previously reported. Loss of heterozygosity was detected in two breast tumors from one c.3507_3508delTC mutation carrier but not in other available tumors from that family or in tumors from carriers of other mutations. CONCLUSIONS: PALB2 mutation screening identifies a small, but significant number of mutations in BRCA1/2 -negative breast and/or ovarian cancer families. We show that mutations are more likely to be found in families with three or more breast cancers as well as other BRCA2-related cancers. In our cohort, both clearly pathogenic mutations were identified in premenopausal breast cancer cases (2/77, 2.6%). Testing should be preferentially offered to affected women from such families.

Feasibility Study and Clinical Impact of Incorporating Breast Tissue Density in High-Risk Breast Cancer Screening Assessment.

Breast tissue density (BTD) is known to increase the risk of breast cancer but is not routinely used in the risk assessment of the population-based High-Risk Ontario Breast Screening Program (HROBSP). This prospective, IRB-approved study assessed the feasibility and impact of incorporating breast tissue density (BTD) into the risk assessment of women referred to HROBSP who were not genetic mutation carriers. All consecutive women aged 40-69 years who met criteria for HROBSP assessment and referred to Genetics from 1 December 2020 to 31 July 2021 had their lifetime risk calculated with and without BTD using Tyrer-Cuzick model version 8 (IBISv8) to gauge overall impact. McNemar's test was performed to compare eligibility with and without density. 140 women were referred, and 1 was excluded (BRCA gene mutation carrier and automatically eligible). Eight of 139 (5.8%) never had a mammogram, while 17/131 (13%) did not have BTD reported on their mammogram and required radiologist review. Of 131 patients, 22 (16.8%) were clinically impacted by incorporation of BTD: 9/131 (6.9%) became eligible for HROBSP, while 13/131 (9.9%) became ineligible (p = 0.394). It was feasible for the Genetics clinic to incorporate BTD for better risk stratification of eligible women. This did not significantly impact the number of eligible women while optimizing the use of high-risk supplemental MRI screening.

Adjuvant docetaxel for node-positive breast cancer.

BACKGROUND: We compared docetaxel plus doxorubicin and cyclophosphamide (TAC) with fluorouracil plus doxorubicin and cyclophosphamide (FAC) as adjuvant chemotherapy for operable node-positive breast cancer. METHODS: We randomly assigned 1491 women with axillary node-positive breast cancer to six cycles of treatment with either TAC or FAC as adjuvant chemotherapy after surgery. The primary end point was disease-free survival. RESULTS: At a median follow-up of 55 months, the estimated rates of disease-free survival at five years were 75 percent among the 745 patients randomly assigned to receive TAC and 68 percent among the 746 randomly assigned to receive FAC, representing a 28 percent reduction in the risk of relapse (P=0.001) in the TAC group. The estimated rates of overall survival at five years were 87 percent and 81 percent, respectively. Treatment with TAC resulted in a 30 percent reduction in the risk of death (P=0.008). The incidence of grade 3 or 4 neutropenia was 65.5 percent in the TAC group and 49.3 percent in the FAC group (P<0.001); rates of febrile neutropenia were 24.7 percent and 2.5 percent, respectively (P<0.001). Grade 3 or 4 infections occurred in 3.9 percent of the patients who received TAC and 2.2 percent of those who received FAC (P=0.05); no deaths occurred as a result of infection. Two patients in each group died during treatment. Congestive heart failure and acute myeloid leukemia occurred in less than 2 percent of the patients in each group. Quality-of-life scores decreased during chemotherapy but returned to baseline levels after treatment. CONCLUSIONS: Adjuvant chemotherapy with TAC, as compared with FAC, significantly improves the rates of disease-free and overall survival among women with operable node-positive breast cancer.

Chemotherapy dose--response relationships in non-small cell lung cancer and implied resistance mechanisms.

BACKGROUND: We hypothesized excess resistance factor ("active resistance") gives a dose--response curve (DRC) shoulder, deficiency of a factor required for drug sensitivity ("saturable passive resistance") gives a DRC terminal plateau, and alteration of a factor gives decreased DRC slope. METHOD: We used response rates from published non-small cell lung cancer (NSCLC) clinical studies to estimate mean percent tumor cell kill in each study (assuming cell kill is proportional to tumor volume change) and performed regression and meta-regression analyses of percent cell survival and patient survival vs planned dose-intensity. RESULTS: As single agents, cell kill approached that of combinations only at highest doses. While DRC shape varied between single agents, DRCs for all combinations tested flattened at higher doses. Patient median survival times also failed to vary significantly with dose for any combination. CONCLUSIONS: DRC flattening at higher doses suggests therapy efficacy is limited by deficiency/saturation of factors required for cell killing. Based on this and other clinical observations, we hypothesize: (1) active resistance may modulate cell killing at lower doses, but ability to overcome this by increasing doses is limited by saturable passive resistance (e.g. by non-cycling cells). (2) Cells surviving initial chemotherapy may upregulate active resistance mechanisms (permitting growth despite therapy). (3) If active resistance mechanisms are insufficient for growth/survival, cells may survive until therapy cessation by downregulating metabolism/cycling, becoming temporarily quiescent. This could help explain broad cross-resistance between agents and would imply that improved targeting of non-cycling cells will be required for major improvement in therapy efficacy.

Functionally Null RAD51D Missense Mutation Associates Strongly with Ovarian Carcinoma.

RAD51D is a key player in DNA repair by homologous recombination (HR), and RAD51D truncating variant carriers have an increased risk for ovarian cancer. However, the contribution of nontruncating RAD51D variants to cancer predisposition remains uncertain. Using deep sequencing and case-control genotyping studies, we show that in French Canadians, the missense RAD51D variant c.620C>T;p.S207L is highly prevalent and is associated with a significantly increased risk for ovarian high-grade serous carcinoma (HGSC; 3.8% cases vs. 0.2% controls). The frequency of the p.S207L variant did not significantly differ from that of controls in breast, endometrial, pancreas, or colorectal adenocarcinomas. Functionally, we show that this mutation impairs HR by disrupting the RAD51D-XRCC2 interaction and confers PARP inhibitor sensitivity. These results highlight the importance of a functional RAD51D-XRCC2 interaction to promote HR and prevent the development of HGSC. This study identifies c.620C>T;p.S207L as the first bona fide pathogenic RAD51D missense cancer susceptibility allele and supports the use of targeted PARP-inhibitor therapies in ovarian cancer patients carrying deleterious missense RAD51D variants. Cancer Res; 77(16); 4517-29. ©2017 AACR.

Recurrent spontaneous pneumothoraces and bullous emphysema. A novel mutation causing Birt-Hogg-Dube syndrome.

Birt-Hogg-Dube syndrome (BHDS) is a rare form of classically cystic lung disease that may present with spontaneous pneumothorax. The associated skin manifestations (fibrofolliculomas) are not always present. This article describes a case of spontaneous pneumothorax secondary to bullous emphysema in an otherwise healthy gentleman caused by a novel mutation in the folliculin (FLCN) gene.

Genetic testing: when prediction generates stigmatization.

Using grounded theory methodology, this study examined the experiences of six BRCA1/2 gene mutation carriers (mean age = 38.5 years). Three types of stigmatization were identified: stigmatization by anticipation, stigmatization through rejection, and stigmatization by affiliation. Participants described potential impacts on their womanhood, felt threatened by others, and revealed fears that their children would inherit their stigmatization. These findings indicate the importance of psychological support in the follow-up of such patients.

Phase II study of alternating chemotherapy regimens for advanced non-small cell lung cancer.

PURPOSE: We assessed the use of alternating drugs with differing mechanisms of action as treatment for advanced non-small cell lung cancer. BACKGROUND: We hypothesized that the shape of a dose-response curve would be determined by the major mechanisms of resistance of a cancer to the drug being studied. Assessment of data from published clinical trials suggested that if our hypothesis were correct resistance of non-small cell lung cancer to most agents is due to "saturable passive" resistance mechanisms (non-competitive inhibition of drug effect due to deficiency of a factor required for drug effect) rather than to "active" resistance mechanisms (competitive inhibition of drug effect due to excess of a factor) or to "non-saturable passive resistance (due to factor alteration or mutation). Using drugs with differing mechanisms of action is a strategy that might be of value against passive resistance. METHOD: In patients with advanced non-small cell lung cancer, we used four alternating cisplatin-based regimens. In each regimen, cisplatin 80 mg/m(2) was given iv on day 1 of each course. The regimens were: cisplatin + vinorelbine 25 mg/m(2) days 1, 8 and 15, cisplatin + gemcitabine 1000 mg/m(2) days 1, 8 and 15, cisplatin + paclitaxel 200 mg/m(2) day 1 iv over 1h, and cisplatin + etoposide 100 mg/m(2) po days 1-6. Patients were assigned randomly to different regimen sequences. Patients first received 1 course of each of these 4 regimens, then received 1 further course of each of single agent vinorelbine, gemcitabine, paclitaxel and etoposide (at the same doses as in courses 1-4), without cisplatin. (Cisplatin was omitted from courses 5-8 to limit cumulative toxicity.) Change in tumor size was measured after each course. RESULTS: Thirty-six patients were entered. One patient achieved complete remission and nine achieved partial remissions, for an objective response rate of 28% (95% confidence intervals, 13-43%). Nineteen patients (53%) (95% confidence intervals, 37-69%) had stable disease. Eleven patients had growth of >10% on one regimen followed by tumor shrinkage of >10% on a later one. Median survival was 8.1 months, 1-year survival was 28% and 2-year survival was 6%. No unexpected toxicity was seen. CONCLUSIONS: The use of four alternating regimens is feasible in advanced non-small cell lung cancer. Response rates and survival times were comparable to those observed for standard chemotherapy approaches, suggesting that this strategy does not offer any major advantage. We plan to explore the hypothesis that this approach failed since tumor cells surviving first exposure to chemotherapy rapidly down-regulate their ability to undergo apoptosis.

Germline and somatic SMARCA4 mutations characterize small cell carcinoma of the ovary, hypercalcemic type.

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is the most common undifferentiated ovarian malignancy in women under 40 years of age. We sequenced the exomes of six individuals from three families with SCCOHT. After discovering segregating deleterious germline mutations in SMARCA4 in all three families, we tested DNA from a fourth affected family, which also carried a segregating SMARCA4 germline mutation. All the familial tumors sequenced harbored either a somatic mutation or loss of the wild-type allele. Immunohistochemical analysis of these cases and additional familial and non-familial cases showed loss of SMARCA4 (BRG1) protein in 38 of 40 tumors overall. Sequencing of cases with available DNA identified at least one germline or somatic deleterious SMARCA4 mutation in 30 of 32 cases. Additionally, the SCCOHT cell line BIN-67 had biallelic deleterious mutations in SMARCA4. Our findings identify alterations in SMARCA4 as the major cause of SCCOHT, which could lead to improvements in genetic counseling and new treatment approaches.

Canadian guideline on genetic screening for hereditary renal cell cancers.

BACKGROUND: Hereditary renal cell cancer (RCC) is an ideal model for germline genetic testing. We propose a guideline of hereditary RCC specific criteria to suggest referral for genetic assessment. METHODS: A review of the literature and stakeholder resources for existing guidelines or consensus statements was performed. Referral criteria were developed by expert consensus. RESULTS: The criteria included characteristics for patients with RCC (age ≤45 years, bilateral or multifocal tumours, associated medical conditions and non-clear cell histologies with unusual features) and for patients with or without RCC, but a family history of specific clinical or genetic diagnoses. CONCLUSIONS: This guideline represents a practical RCC-specific reference to allow healthcare providers to identify patients who may have a hereditary RCC syndrome, without extensive knowledge of each syndrome. RCC survivors and their families can also use the document to guide their discussions with healthcare providers about their need for referral. The criteria refer to the most common hereditary renal tumour syndromes and do not represent a comprehensive or exclusive list. Prospective validation of the criteria is warranted.

Multigene panels in prostate cancer risk assessment.

OBJECTIVES: The aim of this review is to identify, synthesize, and appraise the literature on the analytic validity, clinical validity, and clinical utility of commercially available single nucleotide polymorphism (SNP) panel tests for assessing the risk of prostate cancer. DATA SOURCES: MEDLINE®, Cochrane CENTRAL, Cochrane Database of Systematic Reviews, and Embase, from the beginning of each database to October 2011. Search strategies used combinations of controlled vocabulary (medical subject headings, keywords) and text words. Grey literature was identified. REVIEW METHODS: Three Key Questions (KQs) encompassing broad aspects of the analytic validity, clinical validity, and clinical utility of SNP-based panels were developed with the input of a Technical Expert Panel assembled by the Evidence-based Practice Center and approved by the Agency for Healthcare Research and Quality. Standard systematic review methodology was applied, with eligibility criteria developed separately for each KQ. RESULTS: From 1,998 unique citations, 14 were retained for data abstraction and quality assessment following title and abstract screening and full text screening. All focused on clinical validity (KQ2), and evaluated 15 individual panels with two to 35 SNPs. All had poor discriminative ability for predicting risk of prostate cancer and/or distinguishing between aggressive and asymptomatic/latent disease. The risk of bias of the studies was determined to be moderate. None of the panels had been evaluated in routine clinical settings. CONCLUSIONS: The evidence on currently available SNP panels does not permit meaningful assessment of analytic validity. The limited evidence on clinical validity is insufficient to conclude that the panels assessed would perform adequately as screening or risk stratification tests. No evidence is available on the clinical utility of current panels.