Abstract P2-09-02: Panel testing for familial breast cancer: Tension at the boundary of research and clinical care

Gene panel sequencing is revolutionizing germline risk assessment for hereditary breast cancer. Despite scant evidence supporting the role of many of these genes in breast cancer predisposition, results are often reported to families as the definitive explanation for their family history. We assessed the frequency of mutations in 18 genes commonly included in hereditary breast cancer panels among 2,000 index cases from breast cancer families and 1,997 population controls. Cases were predominantly breast cancer-affected women referred to specialized familial cancer centers (BRCA1 and BRCA2 wild-type). Controls were cancer-free women from the LifePool study (www.lifepool.org). Sequencing data were filtered for known pathogenic or novel loss of function mutations.

The frequency of pathogenic mutations in BRCA1 and BRCA2 in the control group was 0.2% (4 mutations) and 0.4% (8 mutations), respectively, which is consistent with previous indirect estimates for Caucasian populations but to our knowledge this the largest direct assessment of their prevalence.

Excluding 18 mutations identified in BRCA1 and BRCA2 among the cases and controls, a total of 69 cases (3.5%) and 26 controls (1.3%) were found to carry an "actionable mutation". PALB2 was most frequently mutated (22 cases, 3 controls), while no mutations were identified in PTEN or STK11. Among the remaining genes, loss of function mutations were rare with similar frequency between cases and controls.

The frequency of mutations in most breast cancer panel genes among individuals selected for possible hereditary breast cancer is low and in many cases similar or even lower than that observed among cancer-free population controls. While multi-gene panels can significantly aid in cancer risk management, they equally have the potential to provide clinical misinformation and harm at the individual level if the data is not interpreted cautiously.

Citation Format: Campbell IG, Thompson ER, Rowely SM, Li N, McInerny S, Devereux L, Wong-Brown MW, Trainer AH, Mitchell G, Scott RJ, James PA. Panel testing for familial breast cancer: Tension at the boundary of research and clinical care. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-09-02.

On reconstructing Giraffa sivalensis, an extinct giraffid from the Siwalik Hills, India

Giraffa sivalensis occurred during the Plio-Pleistocene period and probably represents the terminal species of the genus in Southern Asia. The holotype is an almost perfectly preserved cervical vertebra of disputed anatomical location. Although there is also uncertainty regarding this animal's size, other specimens that have been assigned to this species include fragments of two humeri, a radius, metacarpi and teeth. Here we estimate neck length, leg length and body mass using interspecific and, unusually, ontogenetic allometry of extant giraffe skeletal parameters. The appropriateness of each equation to estimate body mass was evaluated by calculating the prediction error incurred in both extant giraffes (G. camelopardalis) and okapis (Okapia johnstoni). It followed that the equations with the lowest prediction error in both species were considered robust enough to use in G. sivalensis. The size of G. sivalensis, based on the holotype, is proposed as 400 kg (range 228 kg-575 kg), with a neck length of approximately 147 cm and a height of 390 cm. The molar lengths of tooth specimens considered agree with this size estimate. The humerus was the most appropriate long bone to establish body mass, which estimates a heavier animal of ca 790 kg. The discrepancy with the vertebral body weight estimate might indicate sexual dimorphism. Radial and metacarpal specimens estimate G. sivalensis to be as heavy as extant giraffes. This may indicate that the radius and metacarpus are unsuitable for body mass predictions in Giraffa spp. Alternatively, certain long bones may have belonged to another long legged giraffid that occurred during the same period and locality as G. sivalensis. We have concluded that if sexual dimorphism was present then males would have been about twice the size of females. If sexual dimorphism was not present and all bones were correctly attributed to this species, then G. sivalensis had a slender neck with a relatively stocky body.

BRCA1 and BRCA2 genetic testing-pitfalls and recommendations for managing variants of uncertain clinical significance

BACKGROUND

Increasing use of BRCA1/2 testing for tailoring cancer treatment and extension of testing to tumour tissue for somatic mutation is moving BRCA1/2 mutation screening from a primarily prevention arena delivered by specialist genetic services into mainstream oncology practice. A considerable number of gene tests will identify rare variants where clinical significance cannot be inferred from sequence information alone. The proportion of variants of uncertain clinical significance (VUS) is likely to grow with lower thresholds for testing and laboratory providers with less experience of BRCA. Most VUS will not be associated with a high risk of cancer but a misinterpreted VUS has the potential to lead to mismanagement of both the patient and their relatives.

DESIGN

Members of the Clinical Working Group of ENIGMA (Evidence-based Network for the Interpretation of Germline Mutant Alleles) global consortium (www.enigmaconsortium.org) observed wide variation in practices in reporting, disclosure and clinical management of patients with a VUS. Examples from current clinical practice are presented and discussed to illustrate potential pitfalls, explore factors contributing to misinterpretation, and propose approaches to improving clarity.

RESULTS AND CONCLUSION

Clinicians, patients and their relatives would all benefit from an improved level of genetic literacy. Genetic laboratories working with clinical geneticists need to agree on a clinically clear and uniform format for reporting BRCA test results to non-geneticists. An international consortium of experts, collecting and integrating all available lines of evidence and classifying variants according to an internationally recognized system, will facilitate reclassification of variants for clinical use.

Scaling of the appendicular skeleton of the giraffe (Giraffa camelopardalis)

Giraffes have remarkably long and slender limb bones, but it is unknown how they grow with regard to body mass, sex, and neck length. In this study, we measured the length, mediolateral (ML) diameter, craniocaudal (CC) diameter and circumference of the humerus, radius, metacarpus, femur, tibia, and metatarsus in 10 fetuses, 21 females, and 23 males of known body masses. Allometric exponents were determined and compared. We found the average bone length increased from 340 ± 50 mm at birth to 700 ± 120 mm at maturity, while average diameters increased from 30 ± 3 to 70 ± 11 mm. Fetal bones increased with positive allometry in length (relative to body mass) and in diameter (relative to body mass and length). In postnatal giraffes bone lengths and diameters increased iso- or negatively allometric relative to increases in body mass, except for the humerus CC diameter which increased with positive allometry. Humerus circumference also increased with positive allometry, that of the radius and tibia isometrically and the femur and metapodials with negative allometry. Relative to increases in bone length, both the humerus and femur widened with positive allometry. In the distal limb bones, ML diameters increased isometrically (radius, metacarpus) or positively allometric (tibia, metatarsus) while the corresponding CC widths increased with negative allometry and isometrically, respectively. Except for the humerus and femur, exponents were not significantly different between corresponding front and hind limb segments. We concluded that the patterns of bone growth in males and females are identical. In fetuses, the growth of the appendicular skeleton is faster than it is after birth which is a pattern opposite to that reported for the neck. Allometric exponents seemed unremarkable compared to the few species described previously, and pointed to the importance of neck elongation rather than leg elongation during evolution. Nevertheless, the front limb bones and especially the humerus may show adaptation to behaviors such as drinking posture.

Nutrient-restricted fetus and the cardio–renal connection in hypertensive offspring

A suboptimal intrauterine environment has a number of deleterious effects on fetal development and postpartum health outcomes. Epidemiological studies on several human populations have linked socioeconomic status and low birth weight to an increased incidence of diseases such as hypertension, diabetes, obesity and cardiovascular disease. A growing number of experimental studies in a variety of animal models demonstrate that maternal stressors, such as nutrition and reduced uterine perfusion, affect the intrauterine milieu and result in increased blood pressure in offspring. Several mechanisms appear to contribute to hypertension, including vascular dysfunction and increased peripheral resistance, altered cardio-renal structure and alterations in cardio-renal function. Although many studies have characterized models of developmentally generated hypertension, few have begun to seek therapeutic modalities to ameliorate its incidence. This review discusses recent work that refines hypotheses linking a suboptimal intrauterine environment to cardiovascular and renal phenotypes that have increased susceptibility to cardiovascular disease and hypertension.

Estimating single nucleotide polymorphism associations using pedigree data: applications to breast cancer

BACKGROUND

Pedigrees with multiple genotyped family members have been underutilised in breast cancer (BC) genetic-association studies. We developed a pedigree-based analytical framework to characterise single-nucleotide polymorphism (SNP) associations with BC risk using data from 736 BC families ascertained through multiple affected individuals. On average, eight family members had been genotyped for 24 SNPs previously associated with BC.

METHODS

Breast cancer incidence was modelled on the basis of SNP effects and residual polygenic effects. Relative risk (RR) estimates were obtained by maximising the retrospective likelihood (RL) of observing the family genotypes conditional on all disease phenotypes. Models were extended to assess parent-of-origin effects (POEs).

RESULTS

Thirteen SNPs were significantly associated with BC under the pedigree RL approach. This approach yielded estimates consistent with those from large population-based studies. Logistic regression models ignoring pedigree structure generally gave larger RRs and association P-values. SNP rs3817198 in LSP1, previously shown to exhibit POE, yielded maternal and paternal RR estimates that were similar to those previously reported (paternal RR=1.12 (95% confidence interval (CI): 0.99-1.27), P=0.081, one-sided P=0.04; maternal RR=0.94 (95% CI: 0.84-1.06), P=0.33). No other SNP exhibited POE.

CONCLUSION

Our pedigree-based methods provide a valuable and efficient tool for characterising genetic associations with BC risk or other diseases and can complement population-based studies.

Are we being overly cautious? A qualitative inquiry into the experiences and perceptions of treatment-focused germline BRCA genetic testing amongst women recently diagnosed with breast cancer

PURPOSE

Women with breast cancer, who are found to be BRCA1/2 mutation carriers, have a high risk of ovarian cancer and metachronous breast cancer. Treatment-focused genetic testing (TFGT), offered around the time of diagnosis, allows genetic test results to inform surgical treatment decisions. However, concern has been raised that offering TFGT at this time may overly increase psychological burden. This study aimed to qualitatively explore women's attitudes and experiences of TFGT.

METHODS

Women who had been diagnosed with breast cancer at age 50 years or less undertook a semi-structured telephone interview (n = 26). The sample included women who had been offered TFGT, based on family history and/or other risk criteria (n = 14), and women who had been diagnosed within the past 6-12 months and had not been offered TFGT (n = 12). Interviews explored women's attitudes towards TFGT, perceived benefits and disadvantages, implications of TFGT and impact on surgical decision making. Interviews were transcribed verbatim and thematically analysed.

RESULTS

Women expressed positive attitudes towards TFGT and felt it was highly relevant to their surgical decision making. They did not feel that an offer of TFGT shortly after, or at the time of diagnosis, added undue psychological burden. The majority of women interviewed felt that TFGT should be incorporated into standard clinical care.

CONCLUSIONS

TFGT is viewed favourably by women newly diagnosed with breast cancer. Future randomized controlled trials are needed to examine the long-term impact of TFGT. We conclude that an offer of TFGT is not perceived as 'too much, too soon' by relevant patients.