How common is familial cancer?

Familial risks in nervous system tumours: joint Nordic study

Background:

Familial nervous system cancers are rare and limited data on familial aspects are available particularly on site-specific tumours.

Methods:

Data from five Nordic countries were used to analyse familial risks of nervous system tumours. Standardised incidence ratios (SIRs) were calculated for offspring of affected relatives compared with offspring of non-affected relatives.

Results:

The total number of patients with nervous system tumour was 63 307, of whom 32 347 belonged to the offspring generation. Of 851 familial patients (2.6%) in the offspring generation, 42 (4.7%) belonged to the families of a parent and at least two siblings affected. The SIR of brain tumours was 1.7 in offspring of affected parents; it was 2.0 in siblings and 9.4 in families with a parent and sibling affected. For spinal tumours, the SIRs were much higher for offspring of early onset tumours, 14.0 for offspring of affected parents and 22.7 for siblings. The SIRs for peripheral nerve tumours were 16.3 in offspring of affected parents, 27.7 in siblings and 943.9 in multiplex families.

Conclusion:

The results of this population-based study on medically diagnosed tumours show site-, proband- and age-specific risks for familial tumours, with implications for clinical genetic counselling and identification of the underlying genes.

Prevalence of family history of breast, colorectal, prostate, and lung cancer in a population-based study

BACKGROUND

A positive family history is a known risk factor for several cancers; thus, obtaining a thorough family cancer history is essential in cancer risk evaluation and prevention management.

METHODS

The Family Health Study, a telephone survey in Connecticut, was conducted in 2001. A total of 1,019 participants with demographic information and family cancer history were included in this study. Prevalence of a positive family history of breast, colorectal, prostate, and lung cancer for first- and second-degree relatives was estimated. Logistic regression was used to compare prevalence by demographic factors.

RESULTS

A positive family history among first-degree relatives was reported by 10.9% (95% Confidence Interval, CI = 8.8-13.3) of respondents for breast cancer, 5.1% (95% CI = 3.9-6.7) for colorectal cancer, 7.0% (95% CI = 5.2-9.4) for prostate cancer, and 6.4% (95% CI = 4.9-8.3) for lung cancer. The reported prevalence of family history of specific cancers varied by sex, age and race/ethnicity of the respondents.

CONCLUSION

Family history prevalence for 4 of the most common adult solid tumors is substantial and the reported prevalence varied by respondent characteristics. Additional studies are needed to evaluate tools to promote accurate reporting of family history of cancer.

Germline mutations and polymorphisms in the origins of cancers in women

Several female malignancies including breast, ovarian, and endometrial cancers can be characterized based on known somatic and germline mutations. Initiation and propagation of tumors reflect underlying genomic alterations such as mutations, polymorphisms, and copy number variations found in genes of multiple cellular pathways. The contributions of any single genetic variation or mutation in a population depend on its frequency and penetrance as well as tissue-specific functionality. Genome wide association studies, fluorescence in situ hybridization, comparative genomic hybridization, and candidate gene studies have enumerated genetic contributors to cancers in women. These include p53, BRCA1, BRCA2, STK11, PTEN, CHEK2, ATM, BRIP1, PALB2, FGFR2, TGFB1, MDM2, MDM4 as well as several other chromosomal loci. Based on the heterogeneity within a specific tumor type, a combination of genomic alterations defines the cancer subtype, biologic behavior, and in some cases, response to therapeutics. Consideration of tumor heterogeneity is therefore important in the critical analysis of gene associations in cancer.

Familial association of pancreatic cancer with other malignancies in Swedish families

Background:

The aim of this study was to characterise the familial association of pancreatic cancer with other malignancies.

Methods:

Relative risks (RRs) of pancreatic cancer according to family history of cancer were calculated using the updated Swedish Family-Cancer Database, which includes over 11.5 million individuals. Estimates were based on Poisson regression. RRs of tumours for individuals with a parental history of pancreatic cancer were also estimated.

Results:

The risk of pancreatic cancer was elevated in individuals with a parental history of cancers of the liver (RR 1.41; 95% CI 1.10–1.81), kidney (RR 1.37; 95% CI 1.06–1.76), lung (RR 1.50; 95% CI 1.27–1.79) and larynx (RR 1.98; 95% CI 1.19–3.28). Associations were also found between parental history of pancreatic cancer and cancers of the small intestine, colon, breast, lung, testis and cervix in offspring. There was an increased risk of pancreatic cancer associated with early-onset breast cancer in siblings.

Conclusion:

Pancreatic cancer aggregates in families with several types of cancer. Smoking may contribute to the familial aggregation of pancreatic and lung tumours, and the familial clustering of pancreatic and breast cancer could be partially explained by inherited mutations in the BRCA2 gene.

Bias correction of estimates of familial risk from population-based cohort studies

BACKGROUND

In addition to guiding molecular epidemiology investigations, estimates of the increased risk of disease in relatives of affected persons are also important for screening and counselling decisions. Since precise estimation of such familial risks (FRs) requires large sample sizes, many of the estimates in common use have been obtained from historical electronic records of disease in entire populations, where the relatives of affected and unaffected persons are compared. These estimates may be biased due to failure to identify relatives as affected if they are diagnosed before the start-up date of disease registration.

METHODS

This article presents a method for correcting the bias in FR estimates from such misclassification of family history, using a simple formula that depends on the prevalence and sensitivity of the observed family history. The sensitivity is estimated by using the R package poplab to create realistic populations of related individuals and then imposing the start-up effect of disease registration.

RESULTS

For a range of FRs, the truncation of family history is demonstrated to result in non-differential misclassification, and sensitivity that has little or no dependence on the FR. The bias is most pronounced for high FRs and for registers with a short life span, and increases with the age of the study cohort. In all the situations studied, the bias-corrected estimates are in excellent agreement with the true values.

CONCLUSIONS

In summary, our method can correct the inevitable bias in FRs induced by using electronic population data, and is a feasible alternative to the use of validation samples.

Familial risks in nervous-system tumours: a histology-specific analysis from Sweden and Norway

BACKGROUND

There are limited data available on tumour subtype-specific familial risks for nervous-system tumours. We aimed to provide such data at the population level.

METHODS

We used data from the nationwide Swedish and Norwegian databases on familial cancer to calculate standardised incidence ratios (SIRs) for the familial risk of developing a nervous-system tumour in offspring born after 1931 (Sweden) or 1900 (Norway) whose parents or siblings were probands.

FINDINGS

54 195 patients had nervous-system tumours, 22 331 of whom belonged to the offspring generation aged 0-72 years in Sweden and 0-51 years in Norway. Of 709 familial patients in the offspring generation, 438 (61.8%) had a parent affected by a nervous-system tumour (SIR 1.66; 95% CI 1.51-1.82), 236 (33.3%) had a sibling affected by a nervous-system tumour (SIR 2.01; 95% CI 1.76-2.28), and 35 (4.9%) belonged to families with a parent and at least two siblings affected by a nervous-system tumour (multiplex families; SIR 13.40; 95% CI 9.33-18.66). The SIR for glioma was 1.8 (1.5-2.0) when a parent was a proband, but increased to 11.2 (5.7-19.5) in multiplex families. Early-onset neurinoma and haemangioma showed high familial risks; with an SIR for neurinoma of 1.7 (1.4-2.2) for offspring of affected parents, 2.7 (2.0-3.5) for siblings, and 27.2 (13.5-48.8) for multiplex families, and an SIR for haemangioma of 2.4 (1.4-3.8) for offspring of affected parents. Histology-specific population-based familial risks were shown for meningioma (1.6 for offspring of affected parents; 95% CI 1.3-2.0), ependymoma (2.7 for young offspring <20 years; 1.1-5.5), medulloblastoma (4.1 for siblings; 1.7-8.1), and neuroblastoma (3.2 for siblings; 1.1-6.9).

INTERPRETATION

Our results suggest a complex genetic background for nervous-system tumours, which differs depending on the age of onset and histological subtype of the tumour. High sibling risks might suggest recessive inheritance. As the high-penetrant multiplex families only accounted for about 5% of familial nervous-system tumours, most familial cases are probably caused by low-penetrance genes.

FUNDING

The Nordic Cancer Union, Deutsche Krebshilfe, the Swedish Cancer Society, and the Swedish Council for Working Life and Social Research.