National database of familial cancer in Sweden

Pancreatic cancer risk to siblings of probands in bilineal cancer settings

PURPOSE

Pancreatic cancer (PC) risk is increased in families, but PC risk and risk perception have been understudied when both parents have cancer.

METHODS

An unbiased method defining cancer triads (proband with PC and both parents with cancer) in a prospective registry estimated risk of PC to probands' siblings in triad group 1 (no parent with PC), group 2 (1 parent with PC), and group 3 (both parents with PC). We estimated standardized incidence ratios (SIRs) using a Surveillance, Epidemiology, and End Results (SEER) reference. We also estimated the risk when triad probands carried germline pathogenic/likely pathogenic variants in any of the 6 PC-associated genes (ATM, BRCA1, BRCA2, CDKN2A, MLH1, and TP53). PC risk perception/concern was surveyed in siblings and controls.

RESULTS

Risk of PC was higher (SIR = 3.5; 95% CI = 2.2-5.2) in 933 at-risk siblings from 297 triads. Risk increased by triad group: 2.8 (95% CI = 1.5-4.5); 4.5 (95% CI = 1.6-9.7); and 21.2 (95% CI = 4.3-62.0). SIR in variant-negative triads was 3.0 (95% CI = 1.6-5.0), whereas SIR in variant-positive triads was 10.0 (95% CI = 3.2-23.4). Siblings' perceived risk/concern of developing PC increased by triad group.

CONCLUSION

Sibling risks were 2.8- to 21.2-fold higher than that of the general population. Positive variant status increased the risk in triads. Increasing number of PC cases in a triad was associated with increased concern and perceived PC risk.

Are African primary physicians suspicious enough? Challenges of multiple myeloma diagnosis in Africa

Background

Multiple myeloma is a hematological malignancy of plasma cells belonging to a spectrum of monoclonal protein-secreting disorders known as paraproteinemias. It is classically characterized by accumulated plasma cells in the bone marrow, renal insufficiency, hypercalcemia, and bone lesions (CRAB). Despite studies in the USA indicating that the incidence of multiple myeloma is twice as much in Americans of African descent compared to white Americans and those of Asian descent, African countries have some of the lowest incidence rates and prevalence of the cancer. It is generally thought that this is not entirely factual given the paucity of research into the cancer in sub-Saharan Africa, coupled with other diagnostic challenges such as economic hardships, and poor health-seeking behaviors. In this mini review, we explored the state of multiple myeloma diagnosis across sub-Saharan Africa, outlining the challenges to diagnosis and proposing possible solutions.

Main body

Due to the lack of routine checkups in people > 40 years across sub-Saharan Africa, monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) are often accidentally diagnosed. This is due to a very low awareness of multiple myeloma among primary care clinicians and the general population. Other major challenges to multiple myeloma diagnosis across Africa include a chronic shortage of human resource (pathologists, cytotechnologists, and histotechnologists), and a prohibitive cost of diagnostic services that discourages early diagnosis.

Conclusion

To improve multiple myeloma diagnosis in Africa, a systems approach to thinking among policy makers, philanthropic organizations, and oncologists must be adopted. Governments must invest in health insurance coverage for cancer patients concurrently with heavy investments in human resource training and diagnostic infrastructure scale up. Creative approaches such as digital pathology, online training of clinicians, research and capacity building collaborations among African institutions, European and American institutions, and pharmaceutical companies as seen with other cancers should be explored for multiple myeloma too.

Familial aggregation of early-onset cancers

This registry‐linkage study evaluates familial aggregation of cancer among relatives of a population‐based series of early‐onset (≤40 years) cancer patients in Finland. A cohort of 376,762 relatives of early‐onset cancer patients diagnosed between 1970 and 2012 in 40,538 families was identified. Familial aggregation of early‐onset breast, colorectal, brain and other central nervous system (CNS) cancer and melanoma was explored by standardized incidence ratios (SIR), stratified by relatedness. Gender‐, age‐ and period‐specific population cancer incidences were used as reference. Cumulative risks for siblings and offspring of the proband up to age ≤40 years were also estimated. Almost all early‐onset cancers were sporadic (98% or more). Among first‐degree relatives, SIR was largest in colorectal cancer (14, 95% confidence interval 9.72–18), and lowest in melanoma (1.93, 1.05–3.23). Highest relative‐specific SIRs were observed for siblings in families, where also parent had concordant cancer, 90 (43–165) for colorectal cancer and 29 (11–64) for CNS cancer. In spouses, all SIRs were at population level. Cumulative risk of colorectal cancer by age 41 was 0.98% in siblings and 0.10% in population, while in breast cancer the corresponding risks were 2.05% and 0.56%. In conclusion, early‐onset cancers are mainly sporadic. Findings support high familial aggregation in early‐onset colorectal and CNS cancers. Familial aggregation in multiplex families with CNS cancers was mainly attributed to neurofibromatosis and in colorectal cancer to FAP‐ and HNPCC‐syndromes. The pattern of familial aggregation of early‐onset breast cancer could be seen to support very early exposure to environmental factors and/or rare genetic factors.

What's new?

The tendency for certain cancer types to cluster in families generally is explained by shared environmental exposures or inherited mutations. In particular, early‐onset cancer, diagnosed between ages 0 and 40, is considered indicative of familial factors. Here, investigation of cancer risk among more than 376,760 relatives of probands, or individuals with early‐onset cancer, shows that the likelihood of early‐onset cancer affecting even just one other relative in addition to the proband is exceedingly rare. Nearly all early‐onset cancers in the study population were sporadic. Estimated cumulative risks observed for specific cancers may prove useful in the context of genetic counseling.

Scanning the genomes of parents for imprinted loci acting in their un-genotyped progeny

Depending on their parental origin, alleles at imprinted loci are fully or partially inactivated through epigenetic mechanisms. Their effects contribute to the broader class of parent-of-origin effects. Standard methodology for mapping imprinted quantitative trait loci in association studies requires phenotypes and parental origin of marker alleles (ordered genotypes) to be simultaneously known for each individual. As such, many phenotypes are known from un-genotyped offspring in ongoing breeding programmes (e.g. meat animals), while their parents have known genotypes but no phenotypes. By theoretical considerations and simulations, we showed that the limitations of standard methodology can be overcome in such situations. This is achieved by first estimating parent-of-origin effects, which then serve as dependent variables in association analyses, in which only imprinted loci give a signal. As a theoretical foundation, the regression of parent-of-origin effects on the number of B-alleles at a biallelic locus — representing the un-ordered genotype — equals the imprinting effect. The applicability to real data was demonstrated for about 1800 genotyped Brown Swiss bulls and their un-genotyped fattening progeny. Thus, this approach unlocks vast data resources in various species for imprinting analyses and offers valuable clues as to what extent imprinted loci contribute to genetic variability.

Use of census data for construction of fertility history for Danish women

Background: Modern epidemiology increasingly uses data on families. The authors constructed an extended fertility database for women born in Denmark from 1930 onwards by supplementing the existing Fertility Database with household data from the 1970 census. Methods: A fertility history was constructed for all women participating in the 1970 census, but aiming for complete data only for women aged 20 - 39. The fertility history of these women prior to the 1970 census was constructed from the census data including 1,648,813 persons coded as children. An algorithm was used transforming household information into fertility history data by matching women and children according to family position. Children for whom the algorithm gave no match were searched for in the Fertility Database; children not found in the Fertility Database either were searched for manually. The fertility history after the 1970 census was retrieved from the Fertility Database. Results: Using data from the census 1970, 98.5% of the children were linked to a mother, and 99.6% of these links were estimated to be correct, corresponding to 98.1% of the children being linked correctly. In total, 964,720 children of women aged 20 - 39 in 1970 were identified, which was equivalent to 96.6% of the expected live-born children, and to 99.1% of the expected surviving children. Conclusion: Census household data proved to be an excellent data source for construction of fertility histories.

Lung cancer and concurrent or sequential lymphoma: Two case reports with hypersensitivity to bevacizumab and a review of the literature

Non-small cell lung cancer (NSCLC) accounts for ~80% of all cases of lung cancer, and is the leading cause of cancer-related mortality worldwide. The majority of NSCLC cases of are diagnosed at an advanced stage. The outcome of patients with advanced NSCLC is poor with a median survival time of ~12 months in European and American populations. Lymphoproliferative disorders (LPDs) represent a heterogeneous group of expanding lymphoid cells, which occurs as a result of immune dysfunction. LPDs are often associated with primary solid cancers. We report two cases of LPD diagnosed concurrently and successively to NSCLC. The first case presents a 65-year-old female patient with advanced IV stage lung cancer, according to the International Association for the Study of Lung Cancer TNM staging system. The patient developed a concurrent lymphoma and was treated with first-line therapy including six cycles of gemcitabine and cisplatin, however, the patient experienced an adverse drug reaction to bevacizumab, which was administered after gemcitabine and prior to cisplatin. The second case presented a 74-year-old male patient diagnosed with large B cell lymphoma. The patient acheived remission of the illness, however, after one year the patient was diagnosed with squamous cell lung cancer. After three years, the patient underwent surgery, however disease recurrence was identified. Subsequently, the patient was treated with sterotactic radiotherapy and oral chemotherapy. A review of the associated literature was also conducted.

Death causes in breast cancer patients

BACKGROUND

Due to improved outcomes in breast cancer (BCa), the proportion of affected women dying of other causes has increased. Thus, a better survival of BCa requires knowledge of other causes of death.

MATERIALS AND METHODS

Data on the population, cancers, and causes of death were gathered from the nationwide Swedish Family-Cancer Database, enrolling ∼3.68 million Swedish women. A Cox regression model, comparing BCa patients against all other women, was applied. Cause-of-death-specific hazard ratios (HRs) were calculated for both underlying and multiple causes of death.

RESULTS

Among 641 000 deaths from 1987 to 2006, 48,000 were BCa patients. For underlying causes except BCa, the highest cause-specific HRs were found for diseases of pulmonary circulation {1.51 [95% confidence interval (CI) 1.36-1.68]}, suicide [1.39 (1.19-1.63)], and heart failure [1.29 (1.22-1.37)]. For specific multiple causes, the highest ratios were found for external causes [1.86 (1.80-1.91)] and gastrointestinal disease [1.68 (1.62-1.74)].

CONCLUSIONS

Diagnosis of BCa is associated with increased risks of dying of various causes, including external causes, heart failure, diseases of pulmonary circulation, and gastrointestinal disease. The study fulfills the gap in knowledge of death causes in BCa patients and suggests to draw more attention to comorbidities.

The Swedish Family-Cancer Database 2009: prospects for histology-specific and immigrant studies

The Swedish Family-Cancer Database comprises a total of 11.8 million individuals covering the Swedish population of the past 100 years. Version VIII of the Database is described in the present article. Cancer cases were retrieved from the Swedish Cancer Registry for the period 1958-2006, including more than 1 million first primary cancers. The number of familial cancers in offspring is 14,000 when a parent was diagnosed with a concordant (same) cancer and the number of concordant siblings was 6,000. From the year 1993 onwards histopathological data according to the SNOMED classification were used, which entails advantages for certain cancers, such as breast cancer. Even though the specific morphological classification only covers a limited number of years, it does cover most familial cancers in the offspring generation. The Database records the country of birth for each subject. A total of 1.79 million individuals were foreign born, Finns and other Scandinavians being the largest immigrant groups. The cancer incidence in the first-generation immigrants was compared to that in native Swedes using standardised incidence ratios (SIRs) to measure relative risk. The SIRs ranged widely between the immigrant groups, from 1.9-fold for myeloma to 25-fold for melanoma. The differences in SIRs were smaller in the second-generation immigrants. The usefulness and the possible applications of the Family-Cancer Database have increased with increasing numbers of cases, and the numerous applications have been described in some 300 publications. Familial cancer studies are in the stimulating interphase of the flourishing disciplines of genetics and epidemiology.

Clustering of cancer among families of cases with Hodgkin Lymphoma (HL), Multiple Myeloma (MM), Non-Hodgkin's Lymphoma (NHL), Soft Tissue Sarcoma (STS) and control subjects

Background

A positive family history of chronic diseases including cancer can be used as an index of genetic and shared environmental influences. The tumours studied have several putative risk factors in common including occupational exposure to certain pesticides and a positive family history of cancer.

Methods

We conducted population-based studies of Hodgkin lymphoma (HL), Multiple Myeloma (MM), non-Hodgkin's Lymphoma (NHL), and Soft Tissue Sarcoma (STS) among male incident case and control subjects in six Canadian provinces. The postal questionnaire was used to collect personal demographic data, a medical history, a lifetime occupational history, smoking pattern, and the information on family history of cancer. The family history of cancer was restricted to first degree relatives and included relationship to the index subjects and the types of tumours diagnosed among relatives. The information was collected on 1528 cases (HL (n = 316), MM (n = 342), NHL (n = 513), STS (n = 357)) and 1506 age ± 2 years and province of residence matched control subjects. Conditional logistic regression analyses adjusted for the matching variables were conducted.

Results

We found that most families were cancer free, and a minority included two or more affected relatives. HL [(OR_adj (95% CI) 1.79 (1.33, 2.42)], MM (1.38(1.07, 1.78)), NHL (1.43 (1.15, 1.77)), and STS cases (1.30(1.00, 1.68)) had higher incidence of cancer if any first degree relative was affected with cancer compared to control families. Constructing mutually exclusive categories combining "family history of cancer" (yes, no) and "pesticide exposure ≥10 hours per year" (yes, no) indicated that a positive family history was important for HL (2.25(1.61, 3.15)), and for the combination of the two exposures increased risk for MM (1.69(1.14,2.51)). Also, a positive family history of cancer both with (1.72 (1.21, 2.45)) and without pesticide exposure (1.43(1.12, 1.83)) increased risk of NHL.

Conclusion

HL, MM, NHL, and STS cases had higher incidence of cancer if any first degree relative affected with cancer compared to control families. A positive family history of cancer and/or shared environmental exposure to agricultural chemicals play an important role in the development of cancer.

Risk of second malignant neoplasms among lymphoma patients with a family history of cancer

Radiotherapy and chemotherapy are known risk factors for second cancers after lymphoma. The role of genetic influences, however, remains largely unknown. We assessed risk of second cancers associated with family history of any cancer in 41,181 patients with Hodgkin lymphoma (HL) (n = 7,476), non-Hodgkin lymphoma (NHL) (n = 25,941), or chronic lymphocytic leukemia (CLL) (n = 7,764), using a large population-based database. Family history of cancer was based on a diagnosis of any cancer in 110,862 first-degree relatives. We found increased relative risk (RR) (1.81, 95% confidence interval (CI): 1.04-3.16) of breast cancer among HL patient with positive (vs. negative) family history of cancer. Among CLL patients with positive (vs. negative) family history of cancer, we observed elevated risks of bladder (RR = 3.53, 95% CI: 1.31-9.55) and prostate cancer (RR = 2.15, 95% CI: 1.17-3.94). For NHL patients with positive (vs. negative) family history of cancer, we observed non-significantly increased risk of non-melanoma skin cancer (RR = 1.94, 95% CI: 0.86-4.38) and lung cancer (RR = 1.99, 95% CI: 0.73-5.39). Our observations suggest that genetic factors, as measured by positive family history of cancer, may be influential risk-factors for selected second tumors following lymphoproliferative disorders.

Ascertainment and diagnostic accuracy for hematopoietic lymphoproliferative malignancies in Sweden 1964–2003

Population-based cancer registries are widely used to provide key information about cancer incidence, survival, determinants of progression and clues about pathogenesis. To substantially expand the limited data on diagnostic accuracy and completeness for lymphoproliferative (LP) tumors in such databases, we conducted a retrospective investigation of close to 1,000 cases diagnosed during 4 decades in Sweden. We identified and reviewed medical records for 494 LP tumor patients reported to the population-based Swedish Cancer registry and 503 LP tumor patients identified from hospitals in Sweden among patients with LP tumors diagnosed during 1964-2003. The stratified samples were randomly selected from patients according to LP subtype, over 4 equal calendar periods, and among 6 selected hospitals of diverse size and from different geographic regions. We found 97.9% of reported LP tumor cases to fulfill current diagnostic criteria for having an LP tumor and observed 89.7% to have accurate LP tumor subtype. The overall completeness of non-Hodgkin lymphoma, Hodgkin lymphoma and multiple myeloma cases in the Cancer registry was 95-99% but was lower for the more indolent tumors, chronic lymphocytic leukemia (87.9%) and Waldenström's macroglobulinemia (68.1%). We observed increased overall under-ascertainment for patients diagnosed above age 80 (27%) and among individuals diagnosed before 1973 (12%). In conclusion the diagnostic accuracy and completeness for classically defined LP tumor entities in the Swedish Cancer registry is high. However, we found under-ascertainment of patients with indolent LP tumors, particularly among patients diagnosed at older ages, with early-stage disease and diagnosed in earlier years.

Autoimmunity and Susceptibility to Hodgkin Lymphoma: A Population-Based Case–Control Study in Scandinavia

BACKGROUND

Personal history of autoimmune diseases is consistently associated with increased risk of non-Hodgkin lymphoma. In contrast, there are limited data on risk of Hodgkin lymphoma following autoimmune diseases and almost no data addressing whether there is a familial association between the conditions.

METHODS

Using population-based linked registry data from Sweden and Denmark, 32 separate autoimmune and related conditions were identified from hospital diagnoses in 7476 case subjects with Hodgkin lymphoma, 18,573 matched control subjects, and more than 86,000 first-degree relatives of case and control subjects. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) as measures of relative risks for each condition using logistic regression and also applied multivariable hierarchical regression models. All P values are two-sided.

RESULTS

We found statistically significantly increased risks of Hodgkin lymphoma associated with personal histories of several autoimmune conditions, including rheumatoid arthritis (OR = 2.7, 95% CI = 1.9 to 4.0), systemic lupus erythematosus (OR = 5.8, 95% CI = 2.2 to 15.1), sarcoidosis (OR = 14.1, 95% CI = 5.4 to 36.8), and immune thrombocytopenic purpura (OR = infinity, P = .002). A statistically significant increase in risk of Hodgkin lymphoma was associated with family histories of sarcoidosis (OR = 1.8, 95% CI = 1.01 to 3.1) and ulcerative colitis (OR = 1.6, 95% CI = 1.02 to 2.6).

CONCLUSIONS

Personal or family history of certain autoimmune conditions was strongly associated with increased risk of Hodgkin lymphoma. The association between both personal and family histories of sarcoidosis and a statistically significantly increased risk of Hodgkin lymphoma suggests shared susceptibility for these conditions.

Evidence-based gallbladder cancer staging: changing cancer staging by analysis of data from the National Cancer Database

BACKGROUND

A recent revision of the American Joint Committee on Cancer (AJCC) staging for gallbladder cancer (6th Edition) involved some major changes. Most notably, T2N0M0 tumors were moved from stage II to stage IB; T3N1M0 disease was moved from stage III to stage IIB; and T4NxM0 (x = any) tumors were moved from stage IVA to stage III.

METHODS

In order to determine if these changes were justified by data, an analysis of the 10,705 cases of gallbladder cancer collected between 1989 and 1996 in the NCDB was performed. All patients had >5 year follow-up.

RESULTS

The staging according to the 6th Edition provided no discrimination between stage III and IV. Five-year survivals for stage IIA, IIB, III, and IV (6th Edition) were 7%, 9%, 3%, 2% respectively. The data from the National Cancer Database (NCDB) were used to derive a proposed new staging system that builds upon Edition 5 and had improved discrimination of stage groups over previous editions.

CONCLUSIONS

Changes in staging systems should be justified by data. Multicenter databases, including the NCDB, represent important resources for verification of evidence-based staging systems.

Patterns of autoimmunity and subsequent chronic lymphocytic leukemia in Nordic countries

A population-based case-control study was conducted to evaluate risk of developing chronic lymphocytic leukemia (CLL) associated with personal and/or family history of autoimmune and related diseases. Data were obtained for all (n = 7764) patients diagnosed with CLL in Sweden and Denmark over a 40-year period and with linkable relatives, 16,658 matched control subjects, and first-degree relatives of patients (n = 17,991) and control subjects (n = 39,388). Odds ratios (ORs) were calculated to quantify risk of CLL in relation to personal/family history of 32 autoimmune and related disorders. The risk of CLL was significantly increased among subjects with a personal history of pernicious anemia (OR = 1.94; 1.18-3.18), mainly in the 0- to 1-year latency period. A significantly decreased risk of CLL was found among individuals with a personal history of chronic rheumatic heart disease (OR = 0.55; 0.33-0.93), particularly persons with a long latency (10+ years) between the 2 conditions. We found no association between personal or familial occurrence of other autoimmune or related disorders and CLL. If our results are confirmed, mechanistic studies examining how pernicious anemia might promote increased occurrence of CLL and how chronic rheumatic heart disease protects against CLL, perhaps related to long-term antibiotics use, may provide insights to the as-yet-unknown etiology of CLL.

Familial characteristics of autoimmune and hematologic disorders in 8,406 multiple myeloma patients: A population-based case-control study

A population-based case-control study was conducted to evaluate risk of developing multiple myeloma (MM) associated with personal history of autoimmune diseases and occurrence of autoimmune and selected hematologic disorders in first-degree relatives. Data were obtained for all (n = 8,406) MM cases diagnosed in Sweden (1958-1998), with linkable relatives, 16,543 matched controls and first-degree relatives of cases (n = 22,490) and controls (n = 44,436). Odds ratios (ORs) were calculated to quantify the risk of MM in relation to personal/family history of 32 autoimmune disorders. Familial aggregation of malignancies was evaluated in a marginal survival model using relatives as the cohort. The risk for MM was significantly elevated among subjects with a personal history of pernicious anemia (OR = 3.27; 2.22-4.83) and individuals with a family history of systemic lupus erythematosus (OR = 2.66; 1.12-6.32). Compared with controls, relative risk (RR) of MM was significantly increased (RR = 1.67; 1.02-2.73) in relatives of cases, particularly relatives of probands aged > or =65 at diagnosis (RR = 2.50; 1.19-5.27). Risks were nearly 4-fold elevated among female relatives (RR = 3.97; 1.54-10.2) and among relatives of female probands (RR = 3.74; 1.58-8.83). MM cases had more cases of monoclonal gammopathy of undetermined significance (MGUS) among their relatives than controls, but the numbers were too small to be conclusive. There was generally no increase in risk of MM in probands whose relatives had hematologic malignancies other than MM. These findings do not support a strong association between personal/familial autoimmune diseases and MM. However, MM itself shows significant familial aggregation, implicating the etiologic importance of this type of hematological neoplasm and perhaps MGUS in germ line genes.

Cancer characteristics in Swedish families fulfilling criteria for hereditary nonpolyposis colorectal cancer

BACKGROUND & AIMS

The present study quantified the prevalence of families that fulfill the Amsterdam or Bethesda criteria for hereditary nonpolyposis colorectal cancer (HNPCC) in the whole Swedish population and investigated the extent to which tumors in the classified families are HNPCC-related.

METHODS

The families of the Swedish Family-Cancer Database with at least 4 generations (N = 566,877) were classified according to the Amsterdam and the Bethesda criteria. Survival methods were used to assess the risk of cancer in the classified families, the prognosis of cancer patients, and the risk of subsequent malignancies after colorectal adenomas and after colorectal/endometrial adenocarcinomas.

RESULTS

The Bethesda criteria identified 0.9% of all Swedish families and 11.2% of patients with colorectal cancer. Families that fulfilled the Bethesda criteria showed increased risks of cancer in the colorectum, endometrium, small bowel, ovary, stomach, bile ducts, renal pelvis, and ureter; members of Bethesda criteria families were at decreased risks of lung and cervical cancers. The prognosis of cancer in the ureter, renal pelvis, stomach, ovary, and colorectum, but not in the endometrium, was better in Bethesda criteria than in nonclassified families.

CONCLUSIONS

Most malignancies in the classified families reflect typical features of HNPCC (association with subsequent malignancies, accelerated adenoma-carcinoma sequence, and better survival). The data presented in this study should help to define surveillance strategies for members of families that fulfill the criteria for HNPCC testing.

Familial Risk of Cancer Shortly After Diagnosis of the First Familial Tumor

BACKGROUND

The diagnosis of the first cancer in a family may lead to the medical examination of the patient's relatives and the subsequent identification of additional familial cancers. If detection bias is present, familial risks could be overestimated soon after first diagnosis.

METHODS

We followed 1,677,722 offspring/siblings of 846,448 probands from the year of diagnosis of the first familial tumor to the diagnosis of first cancer, death, emigration, or December 31, 2002, using the Swedish Family Cancer Database. The risks of cancer among the offspring and siblings of patients with melanoma and cancers of the breast, prostate, colorectum, cervix, and lung were compared with those in the general population. Relative risks (RRs) were determined using Poisson regression, according to the time after first diagnosis. All statistical tests were two-sided.

RESULTS

Daughters of women with breast cancer had a statistically significantly higher relative risk of in situ breast cancer during the year of the mother's diagnosis than they did 5 or more years later (RR = 4.78, 95% confidence interval [CI] = 2.16 to 10.6, 26.6 cases per 100,000, versus RR = 1.97, 95% CI = 1.65 to 2.37, 27.2 cases per 100,000; P = .033). Daughters diagnosed the same year as their mothers were younger and were diagnosed earlier in the calendar year than daughters of women diagnosed 5 or more years after their mothers. Similarly, the risk of invasive melanoma among the offspring of individuals with invasive melanoma was higher during the year of the parent's diagnosis than it was 5 or more years afterward (RR = 8.27, 95% CI = 3.82 to 17.9, 57.0 cases per 100,000, versus RR = 3.18, 95% CI = 2.55 to 3.97, 37.6 cases per 100,000; P = .019). Sibling risks of in situ breast cancer, in situ cervical cancer, and invasive prostate cancer also decreased with time after diagnosis of the first familial tumor.

CONCLUSIONS

Increased surveillance may result in the earlier detection of asymptomatic familial cancers, i.e., in detection bias. The possibility of overestimated familial risks of cancer shortly after diagnosis of the first familial tumor should be considered before a patient's clinical and genetic counseling is implemented.

A population-based assessment of the clustering of breast cancer in families eligible for testing of BRCA1 and BRCA2 mutations

BACKGROUND

The prevalence of families eligible for BRCA1/2 mutation testing in the population burden of breast cancer was analysed and the aggregation of breast cancer in these families was explored.

PATIENTS AND METHODS

The families of the Swedish Family-Cancer Database with at least three generations (N=944 723) were classified according to the criteria proposed by the German Consortium for Hereditary Breast and Ovarian Cancer for BRCA1/2 mutation testing. We calculated the proportion of women with breast cancer in the classified families and used standardised incidence ratios (SIRs) to estimate the risk of histology specific breast cancers in families with suspected BRCA1/2 mutations.

RESULTS

Families with two breast cancers before the age of 50 years included 1.8% of the breast cancer patients; 1% of the women with breast cancer belonged to families with breast and ovarian cancers. The SIR of female breast cancer was lowest in families with male breast cancer and highest in families with two women affected by breast cancer under the age of 50 years. The SIRs of medullary breast cancer agreed with the BRCA1 mutation prevalences detected by the German Consortium for Hereditary Breast and Ovarian Cancer.

CONCLUSIONS

Most of the breast malignancies in families with male breast cancer are likely to be related to BRCA2 mutations. Non-BRCA1/2 related effects are probably involved in the strong clustering of breast cancer in families with early onset breast and ovarian cancers.

Familial association of histology specific breast cancers with cancers at other sites

Breast cancer histologies show important differences in their incidence pattern, method of detection and management. Aggregation of breast cancer occurs also in families diagnosed for cancer at sites different from the breast. Therefore, the familial association of histology specific breast cancers with cancers at other sites is of great interest. The nationwide Swedish Family-Cancer Database was used to calculate standardised incidence ratios (SIRs) for breast cancer when parents or sibling were diagnosed with cancer at the most common sites. Significant SIRs were found when parents had breast, ovarian, laryngeal, endometrial, prostate, lung and colon cancers. If women were diagnosed before the age of 50 years, the SIRs were significant when parents were diagnosed with breast, ovarian, and prostate cancers, and leukaemia, and when siblings were diagnosed with squamous cell skin, pancreatic, breast and endometrial cancers. If mothers were diagnosed with breast cancer, histology-specific SIRs were ranked as comedo > tubular > ductal > lobular; SIR for medullary carcinoma was not significant but it was high when mothers presented with ovarian cancer. Other associations were between the upper aerodigestive tract and lobular, colon and comedo, larynx and ductal cancer. Moreover, cervical cancer was associated with comedo and endometrial cancer with the medullary histology. In conclusion, histology-specific breast cancers were associated with specific cancer sites and the strength of the association varied among histologies.

Set-up of a population-based familial breast cancer registry in Geneva, Switzerland: validation of first results

BACKGROUND

This article evaluates the accuracy of family history of breast and ovarian cancer among first-degree relatives of breast cancer patients, retrospectively collected during the setting up of a population-based family breast cancer registry.

PATIENTS AND METHODS

Family histories of cancer for all women with breast cancer recorded at the Geneva Cancer Registry from 1990 to 1999 were retrospectively extracted from medical files. The accuracy of these family histories was validated among Swiss women born in Geneva: all 119 with a family history of breast (n = 110) or ovarian (n = 9) cancer and a representative sample of 100 women with no family history of breast or ovarian cancer. We identified the first-degree relatives of these women with information from the Cantonal Population Office. All first-degree relatives, resident in Geneva from 1970 to 1999, were linked to the cancer registry database for breast and ovarian cancer occurrence. Sensitivity, specificity and level of overall agreement (kappa) were calculated.

RESULTS

Among 310 first-degree relatives identified, 61 had breast cancer and six had ovarian cancer recorded at the Geneva Cancer Registry. The sensitivity, specificity and kappa of the reported family histories of breast cancer were 98%, 97% and 0.97, respectively. For ovarian cancer, the sensitivity, specificity and kappa were 67%, 99%, and 0.66, respectively.

CONCLUSIONS

This study indicates that retrospectively obtained family histories are very accurate for breast cancer. For ovarian cancer, family histories are less precise and may need additional verification.

Population-based study of familial medullary thyroid cancer

BACKGROUND

We wanted to carry out a population-based study on medullary thyroid cancer (MTC) in order to quantify familial risks.

METHODS

MTC was studied in the Swedish Family-Cancer Database, updated in 1999 to cover individuals and offspring, born after 1934 with their biological parents, totaling 9.6 million persons. Cancer data were obtained from the Swedish Cancer Registry from year 1958 to 1996 and included 2,435 thyroid cancers among offspring.

RESULTS

65 offspring were identified with MTC, which was coded as a separate entity since 1985. 62% had neither affected parent nor sib. Most familial cases were diagnosed at ages 15 to 24 and sporadic cases 25 years later. The familial SIRs of MTC were 3,080 and 3,650 when either a parent or a sib had MTC; when both had MTC the SIR was 35,800. All the familial risks were highest in young age groups, 0-9 years. MEN 2 or MEN 2-like families were considered when one family member had a TC and an adrenal pheochromocytoma. SIR of MTC in offspring was 61,000 when a parent had a MEN 2-like cancer and a sib had MTC.

CONCLUSIONS

We described familial and sporadic MTC in a population-based database. The familial risks of MTC may be the highest ever reported in population based studies.

Incidence trends and familial risks in invasive and in situ cutaneous melanoma by sun-exposed body sites

We studied incidence trends, age-incidence relationships and familial risks in invasive and in situ cutaneous melanoma, based on the Swedish Family-Cancer Database of more than 10 million individuals. Offspring were 0-66 years of age. Cancers were obtained from the Swedish Cancer Registry from years 1961-98. The study was based on 9,771 offspring and 22,888 parents with invasive melanoma and 2,446 offspring and 5,017 parents with in situ melanoma. Incidence rates increased markedly for invasive melanoma in the trunk. For in situ melanoma, trunk and head and neck were affected, and, in addition, legs for women. The maximal incidence was around age 80 years, independent of the type or site in men; in women early onset superficially spreading melanoma shifted the age for maximal incidence to about 60 years. For in situ melanoma, lentigo maligna was the main histogenetic type in the head and neck but in the trunk and legs superficially spreading melanoma was somewhat more common. Standardized incidence ratios (SIR) were calculated for familial risk at exposed and covered sites. The combined familial risks for invasive and in situ melanoma were higher at covered (SIR 3.56 from parents) than sun-exposed (1.92 from parents) sites and they agreed when familiality was defined between parents and offspring or between siblings; the sibling SIRs were 3.90 at covered and 2.53 at exposed sites. The data suggest that the higher melanoma density at exposed sites masks familial effects. Furthermore, sun exposure does not appear to reinforce the familial effect.

Familial invasive and in situ squamous cell carcinoma of the skin

We used the updated nation-wide Swedish Family-Cancer Database to examine familial risks in data from 1961 to 1998 on 1252 invasive and 2474 in situ squamous cell carcinoma (SCC) of the skin among offspring, and over 10 times more among parents. In 259 families a parent and an offspring had skin SCC. The familial standardised incidence ratios (SIRs) were 2.72 for invasive and 2.40 for in situ skin cancers in offspring. Multiple skin cancers in parents were associated with increased SIRs for invasive SCC in offspring, being 2.55 for one and up to 14.93 for two invasive and two in situ cancers in parents; the corresponding in situ SCC risks were 2.28 and 7.49. The population attributable fraction for any familial skin SCC, invasive or in situ, was 4.1%. Melanoma was the only discordant tumour that was associated with invasive and in situ skin SCC. These results provide evidence that there is an underlying hereditary susceptibility for at least a part of the familial clustering for skin SCC.

Familial and attributable risks in cutaneous melanoma: effects of proband and age

We studied familial risks in invasive and in situ cutaneous melanoma by comparing the occurrence of melanoma, or discordant cancer, between parents and offspring, and between siblings, based on the Swedish Family Cancer Database of over 10 million individuals. Offspring were 0-66 y of age. Cancers were obtained from the Swedish Cancer Registry from 1961 to 1998. The study was based on 24,818 invasive and 5510 in situ cases of melanoma. Standardized incidence ratios were calculated for familial risk. The standardized incidence ratios for offspring was 2.40 (95% confidence intervals: 2.10-2.72) when only the parent had melanoma and it was 2.98 (95% confidence intervals: 2.54-3.47) when only a sibling was affected; when both a parent and a sibling were affected the standardized incidence ratios was 8.92 (95% confidence intervals: 4.25-15.31). The respective population attributable risks were 1.38, 1.20, and 0.10%. The familial risk showed a clear age dependence and somewhat higher risk in in situ melanoma than in the invasive counterpart. The highest standardized incidence ratio of 61.78 (5.82-227.19) was noted for offspring whose parent had multiple melanomas. Superficially spreading melanoma showed the highest familial risk both among invasive and in situ tumors. Melanoma associated with breast, nervous system, and skin cancers, and in situ melanoma possibly also with connective tissue and thyroid tumors and multiple myeloma.

Environmental and heritable causes of cancer among 9.6 million individuals in the Swedish Family-Cancer Database

The genetic and environmental components in 15 common cancers were estimated using the nationwide Swedish Family-Cancer Database. Tetrachoric correlations were used to describe similarity in cancer liability among family members. Structural equation modeling was used to derive estimates of the importance of genetic and environmental effects. Statistically significant estimates of proportion of cancer susceptibility, accounted for by genetic effects, were obtained for all studied cancers except for leukemia. The estimate was highest in thyroid cancer (53%), followed by tumors at endocrine glands (28%), testis (25%), breast (25%), cervix (22%), melanoma (21%), colon (13%), nervous system (12%), rectum (12%), non-Hodgkin lymphoma (10%), lung (8%), kidney (8%), urinary bladder (7%), stomach (1%) and leukemia (1%). The estimates of shared environmental effects ranged from 0% (cervix) to 15% (stomach). The childhood shared environmental effects were most important in testicular cancer (17%), stomach cancer (13%) and cervix in situ (13%). Our results indicate that environment has a principal causative role in cancer at all studied sites except for thyroid. The relatively large effect of heritability in cancer at some sites, on the other hand, indicates that even though susceptibility genes have been described at many cancer sites, they are likely to explain only part of the genetic effects.

Familial cancer aggregation and the risk of lung cancer

CONTEXT

Around 90% of lung cancer worldwide is attributable to cigarette smoking, although less than 20% of cigarette smokers develop lung cancer. Other factors such as diet, chronic lung diseases, occupation and possibly environmental agents also contribute to this cancer. Genetic factors seem to play a role in lung cancer, but the precise characteristics influencing lung cancer susceptibility are not known, since genetic factors are easily obscured by the strong environmental determinants of lung cancer, particularly smoking.

OBJECTIVE

To estimate the effect that cancer occurrence among first-degree relatives has on the risk of lung cancer.

DESIGN

Hospital-based case-control study.

SETTING

The metropolitan region of São Paulo, Brazil.

PARTICIPANTS

334 incident lung cancer cases and 578 controls matched by hospitals.

MAIN MEASUREMENTS

By means of a structured questionnaire, cases and controls were interviewed about cancer occurrence in first-degree relatives, tobacco smoking, exposure to passive smoking, occupation, migration and socioeconomic status. Non-conditional logistic regression was used to calculate the risk of familial cancer aggregation, the effect of cancer in first-degree relatives and smoking in conjunction, and for controlling confounders.

RESULTS

The adjusted odds ratio (OR) revealed a slight, but not statistically significant, excess risk of lung cancer for subjects with a history of lung cancer in relatives (OR 1.21; 95% confidence interval [CI] 0.50 - 2.92). The same was found among those with a history of other tobacco-related cancers in relatives (OR 1.36; 95% CI 0.87 - 2.14). A step gradient effect was observed regarding lung cancer risk, in accordance with increases in the number of pack-years of cigarette consumption. An interaction between familial cancer aggregation and tobacco smoking was detected.

CONCLUSIONS

A mildly elevated risk of lung cancer among persons with a positive history of lung and other tobacco-related cancers was observed. The finding of an interaction between the variables of familial cancer aggregation and smoking suggests that familial cancer aggregation could be considered as a marker of susceptibility, increasing the risk of lung cancer among smokers. These results improve our knowledge of lung carcinogenesis and can guide future cancer genetic studies.

Time trends in the incidence of cervical and other genital squamous cell carcinomas and adenocarcinomas in Sweden, 1958-1996

OBJECTIVES

We wanted to examine reasons for the different incidence trends for cervical squamous cell carcinoma (SCC, declining) and adenocarcinoma (increasing).

METHODS

The Swedish Family-Cancer Database on 9.6 million individuals was used to derive incidence trends between 1958 and 1996. Cervical cancers were compared to vaginal and vulvar cancers.

RESULTS

A total of 15405 invasive cervical SCCs and 1920 adenocarcinomas were identified. The incidence of SCCs decreased and that of adenocarcinoma increased during the study period, with similar trends among the in situ forms. The incidence of in situ vaginal and vulvar SCC increase 22-fold, whereas, invasive SCC and adenocarcinoma remained unchanged. The age-incidence curves for adenocarcinoma resembled those for SCC before screening, suggesting similar clinical course.

CONCLUSIONS

The data suggest that the increase in the incidence of adenocarcinoma is related to an increasing prevalence of human papilloma virus (HPV) infection in female genitals, perhaps in addition to other factors. The increase is not seen in SCC because of effective screening.

Parental cancer as a risk factor for bone cancer: a nation-wide study from Sweden

We used the nation-wide Swedish Family-Cancer Database to analyze the risk for bone cancer in offspring by parental cancers and in siblings of bone cancer probands. Additionally, the risk of second cancer following childhood bone cancer was investigated. In offspring, 1,190 bone cancers were diagnosed between years 1958 and 1996. Groups of offspring were compared by calculating standardized incidence ratios (SIRs) for bone cancer. Most bone cancer cases occurred sporadically. Parental breast (SIR 1.7) and prostate (SIR 1.7) cancers were associated with early-onset (<25 years) osteosarcoma in offspring, probably due to Li-Fraumeni syndrome. Giant cell sarcoma was increased by parental breast cancer (SIR 2.9), and early-onset chondrosarcoma by parental kidney cancers (SIR 6.8). Bone cancers conveyed a high risk of second bone and connective tissue cancer.

Familial colorectal adenocarcinoma from the Swedish Family-Cancer Database

Familial risks for colorectal (CRC) adenocarcinoma were characterized from the Swedish Family-Cancer Database covering 9.6 million individuals, whose family relationships and cancers were obtained from registered sources, not sensitive to reporting or ascertainment bias. Cancer cases were retrieved from the Swedish Cancer Registry from years 1958-96. Standardized incidence ratios (SIRs) were calculated based on gender-, age-, period- and tumor type specific rates. A total of 4,794 and 67,925 CRCs were recorded in offspring and parents, respectively. For colon and rectal adenocarcinoma, the SIRs in offspring were 2.28 and 1.68 by parental CRC adenocarcinoma, giving attributable proportions of 6.45 and 3.31%, respectively. The SIR of CRC was over 10 when both offspring and parents were diagnosed at a young age. The risk for parental CRC adenocarcinoma was over 100 when 2 or more children were affected. The risk in siblings was also very high when a parent was affected. The familial cancer sites that associated with CRC were those typical of hereditary nonpolyposis colorectal cancer (HNPCC). This is the largest study published on familial CRC and the only one reporting specifically on adenocarcinoma. The data suggest that HNPCC is the largest single disease entity among CRCs, probably accounting for less than 50% of familial CRC. Other familial components appear heterogeneous, characterized by incomplete penetrance, recessive mode of inheritance and few associated tumor sites.

Childhood cancer and parental occupation in the Swedish Family-Cancer Database

We used the nationwide Swedish Family-Cancer Database to analyze the risk for common childhood tumors in offspring in relation to parental occupation recorded in the census of 1960. A total of 8158 cancer cases, diagnosed before age 15 between years 1958 and 1996, were included. Standardized incidence ratios were calculated using 52 different parental occupations. Among the maternal occupations, seven were associated with the risk of cancer in offspring. Assistant nurses had an excess of children with leukemia and connective tissue and colon cancers. Children of female cooks had brain cancers at a rate greater than expected. Fifteen different malignancies were associated with children of male workers. Shoe and leathers workers' children had excesses of many tumors. Among the other paternal occupations associated with childhood tumors, miners, quarrymen, and hairdressers were likely to be exposed to harmful dusts and chemicals.

Apparent anticipation and heterogeneous transmission patterns in familial Hodgkin's and non-Hodgkin's lymphoma: report from a study based on Swedish cancer database

The goal of this study was to test whether there is genetic anticipation in Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). We analyzed 102 parent-child pairs with HD or NHL, based upon the Swedish Cancer Database. We identified 18 sib-pairs (2 HD and 16 NHL) and 102 parent-child pairs (13 HD/HD, 56 NHL/NHL, 25 HD/NHL, and 8 NHL/HD). The mean anticipation score was 27.6 years for all 102 parent-child pairs. The anticipation means were 13.8, 28.4, 19.8 and 35.8 years for these pair-type groups, respectively. These differences between the age of onset for each affected parent-child pair type were statistically significant. The anticipation level was more pronounced among the NHUNHL pairs than in the HD/HD pairs (difference = 12.6 years, p = 0.0003). These results allow us to conclude with confidence that there is an apparent genetic anticipation in familial HD and NHL in the Swedish population.

Gender-specific incidence trends in lung cancer by histological type in Sweden, 1958-1996

We used the Swedish Family-Cancer Database to examine the time trends of lung cancer in Sweden by histological type, with special reference to gender. A total of 45,297 lung cancer cases were analysed. The overall age-adjusted incidence rates of squamous cell carcinoma (SCC) in men peaked in the 1980s and then slightly decreased, while corresponding rates in women increased steadily. The incidence of adenocarcinoma increased in both genders. The male-to-female incidence ratio for SCC was 12.4 in the 1960s and 3.6 in the 1990s. For adenocarcinoma the ratio was close to 1.5 throughout the period. Regression analysis indicated that the birth cohort of the 1940s was at the highest risk for adenocarcinoma in men and for all types of lung cancer in women. Lung cancer in parents was a risk factor for offspring. In conclusion, the data, particularly on women, suggest that modern cigarettes induce lung adenocarcinoma and SCC in a proportion of 1:0.6. This proportion was 1:3.7 among men diagnosed in the 1960s. The incidence ratio of 1.3 for adenocarcinoma between men and women in the 1990s is consistent with the smoking prevalence data a few decades ago, suggesting equal sensitivity of both genders to tobacco-induced lung cancer.

Birth order, family size, and the risk of cancer in young and middle-aged adults

We used the Swedish Family-Cancer Database to analyse the effects of birth order and family size on the risk of common cancers among offspring born over the period 1958-96. Some 1.38 million offspring up to age 55 years with 50.6 million person-years were included. Poisson regression analysis included age at diagnosis, birth cohort, socio-economic status and region of residence as other explanatory variables. The only significant associations were an increasing risk for breast cancer by birth order and a decreasing risk for melanoma by birth order and, particularly, by family size. When details of the women's own reproductive history were included in analysis, birth orders 5-17 showed a relative risk of 1.41. The effects on breast cancer may be mediated through increasing birth weight by birth order. For melanoma, socio-economic factors may be involved, such as limited affordability of sun tourism in large families. Testis cancer showed no significant effect and prostate cancer was excluded from analysis because of the small number of cases.

A population-based study of familial soft tissue tumors

We used the nationwide Swedish Family-Cancer Database to analyze the risk for soft tissue tumors in offspring by parental cancers and in siblings of soft tissue tumor probands. Additionally, risk for second cancer following soft tissue tumor was investigated. In offspring, 1488 soft tissue tumors were diagnosed between years 1958 and 1996. Groups of offspring were compared by calculating standardized incidence ratios (SIRs) for soft tissue tumors. Parental breast, prostate and connective tissue cancers were associated with offspring soft tissue tumors in sex- and age-specific groups. The SIRs were of borderline significance, suggesting a small etiological contribution by Li-Fraumeni syndrome. Soft tissue tumors conveyed a high risk of second soft tissue tumor, probably partially due to recurrences. However, the observed risk for second nervous system cancer was consistent with Li-Fraumeni syndrome. Other associations were unlikely to be due to Li-Fraumeni or other known syndromes, but they could be spurious findings arising from multiple comparisons. Among these, parental stomach cancer (SIR 3.19, 95% CI 1.69-5.17) and endocrine gland tumors (SIR 3.66, 95% CI 1.32-7.17), particularly parathyroid tumors (SIR 4.46, 95% CI 1.41-9.23), were associated with offspring fibrosarcoma, and parental breast cancers with offspring leiomyosarcoma (SIR 2.04, 95% CI 1.08-3.30).

A population-based study of familial cutaneous melanoma

We studied familial risks in cutaneous melanoma by comparing the occurrence of melanoma, or discordant cancer, in two generations, based on the Swedish Family-Cancer Database of 9.6 million individuals. Offspring were from 0 to 61 years of age. Cancers were obtained from the Swedish Cancer Registry for the years 1958 to 1996. The study was based on 30,170 cases of melanoma. Among these, 196 offspring came from families where a parent also presented with melanoma. The overall familial hazard ratio (FHR) was 2.47 when a parent had melanoma; an early age of onset increased the risk. Multiple primary melanomas in parents increased the FHR in offspring, being 2.23 for one, 9.10 for two and up to 83 for more than two melanomas in the parent. The number of affected offspring increased the risk of melanoma in the parents, from 3.05 when one was affected to 5.12 and 151 when two or three offspring were affected, respectively. Melanoma risk to a sibling with an affected proband was 3.56. Melanoma in one generation was associated with an increased occurrence of squamous cell carcinoma of the skin in the other generation. Other weaker associations were found to pancreatic, breast, testicular and nervous system cancers and non-Hodgkin lymphomas.

Sibling risks in cancer: clues to recessive or X-linked genes?

A systematic analysis of cancer risks to offspring and to siblings of cancer cases was carried out based on the nation-wide Swedish Family-Cancer Database. For all 13 cancer sites examined, risks to both offspring and siblings of cases of cancer at the same site were significantly elevated. The relative risk to siblings was approximately 2 fold more than the offspring risk for cancers of the prostate, testis, kidney and bladder, suggesting that recessive or X-linked susceptibility genes may be important for these cancers. Risks to siblings of cases where a parent was also affected were increased >20 fold over population rates for colorectal, ovarian, prostate and renal cancer, and for leukaemia, consistent with the effects of rare high-risk susceptibility alleles.

Cancer risks to spouses and offspring in the Family-Cancer Database

It is generally accepted that cancer is caused by environmental and inherited factors but these are only partially identified. Family studies can be informative but they do not separate shared lifestyles and genes. We estimate familial risks for concordant cancers between spouses in common cancers of both sexes in order to quantify cancer risks from the shared environment. The risks are compared to those seen between parents and offspring in order to estimate the inherited component. The nation-wide Family-Cancer Database was used as the source of family and cancer data. Standardized incidence ratios (SIRs) were calculated for concordant cancer in offspring by parental cancer and in spouses. Among the 23 cancer sites considered, all but two showed an increased SIR for offspring by father or mother. Only two sites, stomach and lung, showed an increase in SIR of concordant cancer among spouses. Additionally, pancreatic cancer and melanoma were increased in couples where at least one spouse was diagnosed before age 50. If both spouses presented melanoma before age 40, SIR was 3.82 for husbands. SIRs of colon, renal, and skin (squamous cell) cancers were unchanged by spouses' concordant cancer. Shared lifestyle among spouses seems to explain only a small proportion of cancer susceptibility. Because lifestyles are likely to differ more between parents and offspring than between spouses, familial cancer risks between parents and offspring are likely to be more due to heritable rather than environmental effects.

Estimation of genetic and environmental components in colorectal and lung cancer and melanoma

Cancer has predominant environmental and somatic causes but the assessment of hereditary (genetic) causes is difficult, except for highly penetrant single-gene causes. Family studies are only partially informative in this regard because family members share diet and life-styles. Twin studies have been classically used to disentangle the effects of heredity and environment on disease etiology. We estimate the genetic and environmental components in colorectal and lung cancer and melanoma by comparing cancer risks in family members. The Swedish Family-Cancer Database, comprising more than 6 million individuals, was used as the source of family and cancer data. Tetrachoric correlations were used to describe similarity in cancer liability among family members. Structural equation modelling was used to derive estimates of the importance of genetic and environmental effects. The estimated genetic component ranged from 10% in colon and colorectal cancer to 18% in melanoma. For lung cancer, the share was 14%. If assortative mating were important for liability to cancer, these heritability estimates may be an underestimation of the true genetic effects. Non-shared environmental effect was 67-68% in colorectal cancer and melanoma, and 71% in lung cancer. Shared and childhood environments were equally important in colorectal cancer and melanoma, whereas no childhood effect was observed for lung cancer.

Multiple primary cancers of the colon, breast and skin (melanoma) as models for polygenic cancers

To assess the role of family history in the development of multiple primary cancer, the Swedish Family-Cancer Database was used to analyze second primary cancer in patients born in 1935 to 1996 with an initial primary cancer of the colon, breast and skin (melanoma) by familial cancer in first-degree relatives. Standardized incidence ratios (SIRs) were calculated from site-, sex- and age-specific rates for all persons (offspring) born in 1935 to 1996. Familial risk (SIR) was calculated for the first and second primary cancers in offspring. A Poisson regression analysis was also performed to assess the risk factors for occurrence of second primary cancer. The familial proportion of multiple primary cancers was 29.0% (9/31) for colon, 16.3% (122/747) for female breast and 14.5% (17/117) for melanoma. Compared with all offspring, patients with family history were at a much higher and significantly increased risk for subsequent primary cancer at colon (SIR = 59.1), skin (SIR = 48.2) and female breast (SIR = 7.9). The corresponding SIRs in patients without family history were 13.8, 10.5 and 5.2 at the three sites. The ratios for incidence of second primary to first primary were highest when diagnosis age was less than 40 years. A Poisson regression analysis showed that family history was one of the major risk factors for occurrence of multiple primary cancers at colon, breast and skin. The high risk of second cancer, even in the absence of family history, would be consistent with a polygenic model of carcinogenesis.

Familial cancer risks in affected sibships: results from the Swedish family-cancer database

We used the nationwide Swedish Family-Cancer Database to assess familial risks to sibs in sibsibs where at least two sibs had concordant cancer and their parents either concordant or discordant cancer. Familial relative risks (FRRs) were calculated by comparing to concordant sib-pairs whose parents had no cancer. Cancer sites were included if at least ten such concordant sib-pairs were found. In situ cancers were included in order to increase the numbers of cases. Concordant triads, one parent and the sib-pair affected, had an FRR over 100 for thyroid (FRR 399), colon, all bowel, and ovarian cancer. In these cancers, some 40% or more of the concordant sib-pairs belonged to this group. Melanoma and cancer of the nervous system showed FRRs of about 20, and invasive breast cancer of only 2. 9; in these cancers no more than 10% of the concordant sib-pairs belonged to the concordant triads. Discordant family sets, one or two parents presenting with a cancer discordant from that of the sib-pair, showed an FRR of about 3.0 and breast cancer about 2.0, suggesting the involvement of familial effects shared by many forms of cancer.

Cancers in the first-degree relatives of children with brain tumours

We used the nationwide Swedish Family-Cancer Database with 2060 childhood brain tumours diagnosed in the period 1958-1996 to analyse the risk of this tumour by parental cancers and in siblings of childhood brain tumour probands. Groups of patients were compared by calculating standardized incidence ratios (SIRs) for brain tumours in offspring. 1.3% of brain tumour patients had a parent with nervous system cancer; SIRs were 2.4 and 1.88 for diagnostic ages < 5 and < 15 years, respectively. The data showed distinct patterns of familial risks for childhood brain tumours, the SIR was 10.26 for brain astrocytoma given a parent with meningioma. Parental colon cancer was associated with offspring ependymoma (SIR 3.70), and parental salivary gland cancers with offspring medulloblastoma (SIR 13.33, but two cases only). SIR for sibling nervous system cancer from childhood brain tumour probands was 3.55 up to age 61.

Familial relationships in squamous cell carcinoma of the skin

The Swedish Family-Cancer Database, which was updated in 1999 to cover individuals born after 1934 with their biological parents, totals 9.6 million persons. We used this resource to study invasive and in situ skin cancers. We identified 198 families in which a parent and an offspring had skin cancer. The familial standardized incidence ratios (SIRs) were 2.4 for invasive and 2.8 for in situ skin cancers in offspring. The SIRs for offspring depended only weakly on the age at diagnosis, as evaluated in two age groups. Compared with offspring whose parents had a single skin cancer, offspring whose parents had multiple skin cancers had a 70% increase in SIR. The discordant parental cancer sites that showed associations with skin cancer in offspring were melanoma, ocular melanoma, and a group of cancers observed in immunosuppressed patients.

Familial prostate cancer from the family-cancer database

The aim of this study was to calculate the familial risk for prostate cancer (PC) for different family relationships. PC was studied in the Swedish Family-Cancer Database, updated in 1999 to cover individuals born after 1934 with their biological parents, totalling 9.6 million persons. Cancer data were obtained from the Swedish Cancer Registry from 1958 to 1996 and included 1035 PC cases amongst offspring. 188 families were identified where a father and a son had PC, giving a familial standardised incidence ratio (SIR) of 2.44 (2.10-2.80). The proportion of familial cancers was 18.2% amongst all PC amongst all PC amongst sons. There were only 5 pairs of affected brothers, of which 3 had an affected father. Age of onset modified familial risks modestly; the highest SIR of 4.43 (1.40-9.17) was for sons diagnosed before 50 years of age when the father was diagnosed before 65 years of age. When analysed across sites, an association of PC in one generation and stomach, liver and skin cancer and myeloma in another generation was observed. The link was most consistent for skin cancer. No maternal site was associated with a son's PC, although the SIR of breast cancer was 1.22 (0.95-1.53). No increased risk of malignancy was observed in wives of affected men excluding any shared environmental effect for PC and female cancers.

Genetic predisposition, environment and cancer incidence: a nationwide twin study in Finland, 1976-1995

Twin studies integrate genetic and environmental (including physical environment and life-style) information by comparing monozygotic and dizygotic twins for the occurrence of disease. Our objectives were to compare cancer incidence in twins with national rates and to estimate both the probability that co-twins of affected twins may develop cancer and the importance of genetic predisposition and environment in cancer development. The nationwide record linkage of the Finnish Twin Cohort Study, the Finnish Cancer Registry and the Central Population Register allowed the follow-up of 12,941 same-sexed twin pairs for incident primary cancers from 1976 to 1995. Zygosity was determined by use of a validated questionnaire in 1975. Methods included calculation of standardized incidence ratios and concordances and fitting of structural equation models. A total of 1,613 malignant neoplasms occurred in the cohort. The overall cancer incidence among twins resembled that among the general population. Monozygotic co-twins of affected twins were at 50% higher risk than were dizygotic co-twins. Based on genetic modeling, inherited genetic factors accounted for 18% (95% confidence interval 4-32%) of the liability in inter-individual variation in the risk of overall cancer, while non-genetic factors shared by twins accounted for 7% (0-16%) and unique environmental factors for 75% (65-85%). Our results appear to exclude a contribution greater than one-third for genetic predisposition in the development of cancer in the general population, thus pointing to the earlier confirmed substantial role of environment.