[Comparison of diagnosis and treatment of invasive breast cancer between Iceland and Sweden].

PURPOSE: As part of the implementation of quality registration in Iceland we used retrospective data to compare diagnosis and treatment of invasive breast cancer between Iceland and Sweden. MATERIALS AND METHODS: Information on all patients diagnosed with invasive breast cancer in Iceland 2016-2017 was obtained from the Icelandic Cancer Registry. Hospital records were used to register variables in an electronic form adapted from the Swedish quality registration, and compared with data from Sweden for the same period. A chi-square test was used to compare ratios. RESULTS: A total of 486 cases of breast cancer were diagnosed in Iceland and 15.325 in Sweden. A lower proportion of 40-69 year old women were diagnosed within the screening programme in Iceland (46%) compared to Sweden (60%) (p<0.01). Multidisciplinary tumor board meetings held before and after surgery were less frequent in Iceland (92% vs. 96%) compared to Sweden (98% vs. 99%) in 2016 (p<0,01) but no difference was seen in 2017. A sentinel node surgery was done in 69% of the cases in Iceland compared to 94% in Sweden (p<0,01). For cancers ≤30mm breast conserving surgery was done in 48% cases in Iceland but 80% in Sweden (p<0,01). In Iceland 87% of the cases had radiation therapy after breast conserving surgery but 94% in Sweden (p<0,01). Among mastectomy patients with lymph node metastases, 49% received radiation therapy in Iceland compared to 83% in Sweden (p<0,01). CONCLUSION: Differences were seen in several areas of diagnosis and treatment of invasive breast cancer between Iceland and Sweden. With quality registration it will be possible to monitor and set goals for the diagnosis and treatment, with the aim of providing the best treatment to as many patients as possible.

Clonal hematopoiesis, with and without candidate driver mutations, is common in the elderly.

Clonal hematopoiesis (CH) arises when a substantial proportion of mature blood cells is derived from a single dominant hematopoietic stem cell lineage. Somatic mutations in candidate driver (CD) genes are thought to be responsible for at least some cases of CH. Using whole-genome sequencing of 11 262 Icelanders, we found 1403 cases of CH by using barcodes of mosaic somatic mutations in peripheral blood, whether or not they have a mutation in a CD gene. We find that CH is very common in the elderly, trending toward inevitability. We show that somatic mutations in TET2, DNMT3A, ASXL1, and PPM1D are associated with CH at high significance. However, known CD mutations were evident in only a fraction of CH cases. Nevertheless, the highly prevalent CH we detect associates with increased mortality rates, risk for hematological malignancy, smoking behavior, telomere length, Y-chromosome loss, and other phenotypic characteristics. Modeling suggests some CH cases could arise in the absence of CD mutations as a result of neutral drift acting on a small population of active hematopoietic stem cells. Finally, we find a germline deletion in intron 3 of the telomerase reverse transcriptase (TERT) gene that predisposes to CH (rs34002450; P = 7.4 × 10-12; odds ratio, 1.37).

Nonsense mutation in the LGR4 gene is associated with several human diseases and other traits.

Low bone mineral density (BMD) is used as a parameter of osteoporosis. Genome-wide association studies of BMD have hitherto focused on BMD as a quantitative trait, yielding common variants of small effects that contribute to the population diversity in BMD. Here we use BMD as a dichotomous trait, searching for variants that may have a direct effect on the risk of pathologically low BMD rather than on the regulation of BMD in the healthy population. Through whole-genome sequencing of Icelandic individuals, we found a rare nonsense mutation within the leucine-rich-repeat-containing G-protein-coupled receptor 4 (LGR4) gene (c.376C>T) that is strongly associated with low BMD, and with osteoporotic fractures. This mutation leads to termination of LGR4 at position 126 and fully disrupts its function. The c.376C>T mutation is also associated with electrolyte imbalance, late onset of menarche and reduced testosterone levels, as well as an increased risk of squamous cell carcinoma of the skin and biliary tract cancer. Interestingly, the phenotype of carriers of the c.376C>T mutation overlaps that of Lgr4 mutant mice.

Why is colon cancer survival improving by time? A nationwide survival analysis spanning 35 years.

There is limited information present to explain temporal improvements in colon cancer survival. This nationwide study investigates the temporal changes in survival over a 35-year period (1970-2004) in Iceland and uses incidence, mortality, surgery rate, stage distribution, lymph node yield, tumor location and histological type to find explanations for these changes. Patients diagnosed with colon cancer in Iceland 1970-2004 were identified (n = 1962). All histopathology was reassessed. Proportions, age-standardized incidence and mortality, relative, cancer-specific and overall survival and conditional survival were calculated. When comparing first and last diagnostic periods (1970-1978 and 1997-2004), 5-year relative survival improved by 12% for men and 9% for women. At the same time surgery rate increased by 12% and the proportion of stage I increased by 9%. Stage-stratified, improved 5-year relative survival was mainly observed in stages II and III and coincided with higher lymph node yields, proportional reduction of stage II cancers and proportional increase of stage III cancers, indicating stage migration between these stages. Improvement in 1-year survival was mainly observed in stages III and IV. Five-year survival improvement for patients living beyond 1 year was minimum to none. There were no changes in histology that coincided with neither increased incidence nor possibly influencing improved survival. Concluding, as a novel finding, 1-year mortality, which previously has been identified as an important variable in explaining international survival differences, is in this study identified as also being important in explaining temporal improvements in colon cancer survival in Iceland.

Genome-wide association study yields variants at 20p12.2 that associate with urinary bladder cancer.

Genome-wide association studies (GWAS) of urinary bladder cancer (UBC) have yielded common variants at 12 loci that associate with risk of the disease. We report here the results of a GWAS of UBC including 1670 UBC cases and 90 180 controls, followed by replication analysis in additional 5266 UBC cases and 10 456 controls. We tested a dataset containing 34.2 million variants, generated by imputation based on whole-genome sequencing of 2230 Icelanders. Several correlated variants at 20p12, represented by rs62185668, show genome-wide significant association with UBC after combining discovery and replication results (OR = 1.19, P = 1.5 × 10(-11) for rs62185668-A, minor allele frequency = 23.6%). The variants are located in a non-coding region approximately 300 kb upstream from the JAG1 gene, an important component of the Notch signaling pathways that may be oncogenic or tumor suppressive in several forms of cancer. Our results add to the growing number of UBC risk variants discovered through GWAS.

Common variants on chromosomes 2q35 and 16q12 confer susceptibility to estrogen receptor-positive breast cancer.

Familial clustering studies indicate that breast cancer risk has a substantial genetic component. To identify new breast cancer risk variants, we genotyped approximately 300,000 SNPs in 1,600 Icelandic individuals with breast cancer and 11,563 controls using the Illumina Hap300 platform. We then tested selected SNPs in five replication sample sets. Overall, we studied 4,554 affected individuals and 17,577 controls. Two SNPs consistently associated with breast cancer: approximately 25% of individuals of European descent are homozygous for allele A of rs13387042 on chromosome 2q35 and have an estimated 1.44-fold greater risk than noncarriers, and for allele T of rs3803662 on 16q12, about 7% are homozygous and have a 1.64-fold greater risk. Risk from both alleles was confined to estrogen receptor-positive tumors. At present, no genes have been identified in the linkage disequilibrium block containing rs13387042. rs3803662 is near the 5' end of TNRC9 , a high mobility group chromatin-associated protein whose expression is implicated in breast cancer metastasis to bone.

Parental origin of sequence variants associated with complex diseases.

Effects of susceptibility variants may depend on from which parent they are inherited. Although many associations between sequence variants and human traits have been discovered through genome-wide associations, the impact of parental origin has largely been ignored. Here we show that for 38,167 Icelanders genotyped using single nucleotide polymorphism (SNP) chips, the parental origin of most alleles can be determined. For this we used a combination of genealogy and long-range phasing. We then focused on SNPs that associate with diseases and are within 500 kilobases of known imprinted genes. Seven independent SNP associations were examined. Five-one with breast cancer, one with basal-cell carcinoma and three with type 2 diabetes-have parental-origin-specific associations. These variants are located in two genomic regions, 11p15 and 7q32, each harbouring a cluster of imprinted genes. Furthermore, we observed a novel association between the SNP rs2334499 at 11p15 and type 2 diabetes. Here the allele that confers risk when paternally inherited is protective when maternally transmitted. We identified a differentially methylated CTCF-binding site at 11p15 and demonstrated correlation of rs2334499 with decreased methylation of that site.

Ancestry-shift refinement mapping of the C6orf97-ESR1 breast cancer susceptibility locus.

We used an approach that we term ancestry-shift refinement mapping to investigate an association, originally discovered in a GWAS of a Chinese population, between rs2046210[T] and breast cancer susceptibility. The locus is on 6q25.1 in proximity to the C6orf97 and estrogen receptor alpha (ESR1) genes. We identified a panel of SNPs that are correlated with rs2046210 in Chinese, but not necessarily so in other ancestral populations, and genotyped them in breast cancer case:control samples of Asian, European, and African origin, a total of 10,176 cases and 13,286 controls. We found that rs2046210[T] does not confer substantial risk of breast cancer in Europeans and Africans (OR = 1.04, P = 0.099, and OR = 0.98, P = 0.77, respectively). Rather, in those ancestries, an association signal arises from a group of less common SNPs typified by rs9397435. The rs9397435[G] allele was found to confer risk of breast cancer in European (OR = 1.15, P = 1.2 x 10(-3)), African (OR = 1.35, P = 0.014), and Asian (OR = 1.23, P = 2.9 x 10(-4)) population samples. Combined over all ancestries, the OR was 1.19 (P = 3.9 x 10(-7)), was without significant heterogeneity between ancestries (P(het) = 0.36) and the SNP fully accounted for the association signal in each ancestry. Haplotypes bearing rs9397435[G] are well tagged by rs2046210[T] only in Asians. The rs9397435[G] allele showed associations with both estrogen receptor positive and estrogen receptor negative breast cancer. Using early-draft data from the 1,000 Genomes project, we found that the risk allele of a novel SNP (rs77275268), which is closely correlated with rs9397435, disrupts a partially methylated CpG sequence within a known CTCF binding site. These studies demonstrate that shifting the analysis among ancestral populations can provide valuable resolution in association mapping.

Colon cancer in Iceland--a nationwide comparative study on various pathology parameters with respect to right and left tumor location and patients age.

Increasing evidence suggests genetic, biological and demographical difference between right and left colon cancer. Studies have also indicated age differences in the pathology of colon cancer. There is a scarcity of large-scale studies that closely examine the pathological differences regarding age and tumor location. The aim of our study was to do an extensive comparison of right- and left- sided colon cancers as well as comparing patients <50 years with older patients. A retrospective, population-based study was carried out on all patients with colon cancer in Iceland between 1955 and 2004. A total of 2293 cases were analyzed (1148 men, 1145 women). All histopathology material was re-evaluated. Differences in tumor characteristics between right and left location and younger (<50) and older (≥50) patients was evaluated in particular. Higher TNM-stage, larger tumors, vessel invasion, mucinous type, high grade and expanding tumor border occurred more frequently in right- versus left-sided lesions while annular and polypoid tumors were more common in left-sided tumors (p < 0.05). Young patients had more frequent lymph node metastases, vessel invasion, nonpolypoid lesions and infiltrating tumor border (p < 0.05). Right-sided lesions show more aggressive features, reflected in morphology and stage. Younger patients present more frequently with adverse features than do older patients. Frequency of right- and left-sided colon cancer differs by age with pronounced age-location differences in females. This supports the assumption of differences in etiology and carcinogenesis of right- and left-sided colon cancer, and between young and old patients.

In situ breast cancer incidence patterns in Iceland and differences in ductal carcinoma in situ treatment compared to Sweden.

The purpose was to review the incidence of in situ carcinoma in Iceland after initiating population-based mammography screening in 1987 and to compare management of ductal carcinoma in situ (DCIS) between Iceland and the Uppsala-Örebro region (UÖR) in Central Sweden. The Icelandic Cancer Registry provided data on in situ breast carcinomas for women between 1957 and 2017. Clinical data for women with DCIS between 2008 and 2014 was extracted from hospital records and compared to women diagnosed in UÖR. In Iceland, in situ carcinoma incidence increased from 7 to 30 per 100 000 women per year, following the introduction of organised mammography screening. The proportion of in situ carcinoma of all breast carcinomas increased from 4 to 12%. More than one third (35%) of women diagnosed with DCIS in Iceland were older than 70 years versus 18% in UÖR. In Iceland, 49% of all DCIS women underwent mastectomy compared to 40% in UÖR. The incidence of in situ carcinoma in Iceland increased four-fold after the uptake of population-based mammography screening causing considerable risk of overtreatment. Differences in treatment of DCIS were seen between Iceland and UÖR, revealing the importance of quality registration for monitoring patterns of management.

Common and Rare Sequence Variants Influencing Tumor Biomarkers in Blood.

BACKGROUND: Alpha-fetoprotein (AFP), cancer antigens 15.3, 19.9, and 125, carcinoembryonic antigen, and alkaline phosphatase (ALP) are widely measured in attempts to detect cancer and to monitor treatment response. However, due to lack of sensitivity and specificity, their utility is debated. The serum levels of these markers are affected by a number of nonmalignant factors, including genotype. Thus, it may be possible to improve both sensitivity and specificity by adjusting test results for genetic effects. METHODS: We performed genome-wide association studies of serum levels of AFP (N = 22,686), carcinoembryonic antigen (N = 22,309), cancer antigens 15.3 (N = 7,107), 19.9 (N = 9,945), and 125 (N = 9,824), and ALP (N = 162,774). We also examined the correlations between levels of these biomarkers and the presence of cancer, using data from a nationwide cancer registry. RESULTS: We report a total of 84 associations of 79 sequence variants with levels of the six biomarkers, explaining between 2.3% and 42.3% of the phenotypic variance. Among the 79 variants, 22 are cis (in- or near the gene encoding the biomarker), 18 have minor allele frequency less than 1%, 31 are coding variants, and 7 are associated with gene expression in whole blood. We also find multiple conditions associated with higher biomarker levels. CONCLUSIONS: Our results provide insights into the genetic contribution to diversity in concentration of tumor biomarkers in blood. IMPACT: Genetic correction of biomarker values could improve prediction algorithms and decision-making based on these biomarkers.

Genome-wide associations for benign prostatic hyperplasia reveal a genetic correlation with serum levels of PSA.

Benign prostatic hyperplasia and associated lower urinary tract symptoms (BPH/LUTS) are common conditions affecting the majority of elderly males. Here we report the results of a genome-wide association study of symptomatic BPH/LUTS in 20,621 patients and 280,541 controls of European ancestry, from Iceland and the UK. We discovered 23 genome-wide significant variants, located at 14 loci. There is little or no overlap between the BPH/LUTS variants and published prostate cancer risk variants. However, 15 of the variants reported here also associate with serum levels of prostate specific antigen (PSA) (at a Bonferroni corrected P < 0.0022). Furthermore, there is a strong genetic correlation, rg = 0.77 (P = 2.6 × 10-11), between PSA and BPH/LUTS, and one standard deviation increase in a polygenic risk score (PRS) for BPH/LUTS increases PSA levels by 12.9% (P = 1.6×10-55). These results shed a light on the genetic background of BPH/LUTS and its substantial influence on PSA levels.

Sequence variant at 4q25 near PITX2 associates with appendicitis.

Appendicitis is one of the most common conditions requiring acute surgery and can pose a threat to the lives of affected individuals. We performed a genome-wide association study of appendicitis in 7,276 Icelandic and 1,139 Dutch cases and large groups of controls. In a combined analysis of the Icelandic and Dutch data, we detected a single signal represented by an intergenic variant rs2129979 [G] close to the gene PITX2 associating with increased risk of appendicitis (OR = 1.15, P = 1.8 × 10-11). We only observe the association in patients diagnosed in adulthood. The marker is close to, but distinct from, a set of markers reported to associate with atrial fibrillation, which have been linked to PITX2. PITX2 has been implicated in determination of right-left symmetry during development. Anomalies in organ arrangement have been linked to increased prevalence of gastrointestinal and intra-abdominal complications, which may explain the effect of rs2129979 on appendicitis risk.

A genome-wide association study yields five novel thyroid cancer risk loci.

The great majority of thyroid cancers are of the non-medullary type. Here we report findings from a genome-wide association study of non-medullary thyroid cancer, including in total 3,001 patients and 287,550 controls from five study groups of European descent. Our results yield five novel loci (all with Pcombined<3 × 10-8): 1q42.2 (rs12129938 in PCNXL2), 3q26.2 (rs6793295 a missense mutation in LRCC34 near TERC), 5q22.1 (rs73227498 between NREP and EPB41L4A), 10q24.33 (rs7902587 near OBFC1), and two independently associated variants at 15q22.33 (rs2289261 and rs56062135; both in SMAD3). We also confirm recently published association results from a Chinese study of a variant on 5p15.33 (rs2736100 near the TERT gene) and present a stronger association result for a moderately correlated variant (rs10069690; OR=1.20, P=3.2 × 10-7) based on our study of individuals of European ancestry. In combination, these results raise several opportunities for future studies of the pathogenesis of thyroid cancer.

A population-based study on the familial aggregation of cutaneous malignant melanoma in Iceland.

The aim of this study was to characterize the familial nature of cutaneous malignant melanoma (CMM) in Iceland. Risk ratio was used to estimate the risk among relatives of all CMM index cases diagnosed in Iceland over a 45-year period (1955-1999), using data from the National Cancer Registry and a genealogy database that covers the whole of Iceland's population. First-, second-, and third-degree relatives of CMM patients did not have an increased risk of the disease, and no added risk of other types of cancer among relatives was observed, except for thyroid cancer in first-degree male relatives. Seven individuals were diagnosed with two or more primary CMM in this period; none of these individuals had a first or second-degree relative with CMM. Altogether, 2.4% of cases were familial, as defined by commonly used criteria. In conclusion, high-penetrance susceptibility genes do not contribute much to CMM in the Icelandic population. The great majority of CMM cases in Iceland are most likely caused by the interplay between environmental causes and low-risk genes.

[Epidemiology of the two types of gastric adenocarcinoma in Iceland according to the Laurén histological classification 1990-2009].

BACKGROUND: In the mid twentieth century gastric cancer was the most common type of cancer in Iceland. In recent decades, however, the incidence rate of gastric cancer has decreased markedly and currently only represents 2-3% of cancer cases. The Laurén classification system classifies adenocarcinoma into two types, intestinal and diffuse. The main purpose of our study was to describe the epidemiology of the two types of gastric adenocarcinoma in Iceland between the years 1990-2009. METHODS: This is a retrospective cohort study. Information on patients diagnosed with gastric cancer in Iceland between 1990 and 2009 was collected from the population based Cancer Registry. Histological descriptions were reviewed and classified according to the Laurén classification system. The records of patients diagnosed with either having intestinal or diffuse adenocarcinomas were reviewed and epidemiological information gathered. RESULTS: Between 1990 and 2009, 730 patients were diagnosed with gastric adenocarcinoma in Iceland, 447 had intestinal adenocarcinoma and 168 diffuse adenocarcinoma. Patients diagnosed with diffuse adenocarcinoma were significantly younger at diagnosis than those diagnosed with intestinal adenocarcinoma. The sex ratio for intestinal adenocarcinoma was 2.3:1 (M:F) and 1.1:1 (M:F) for diffuse adenocarcinoma. The incidence of intestinal adenocarcinoma decreased more rapidly than that of diffuse adenocarcinoma during this period (0.92/100,000 vs. 0.12/100,000). Median survival rates of intestinal and diffuse adenocarcinomas were 23.7 and 20.6 months, respectively. The difference in survival was found to be statistically significant. The hazard ratio between the two groups was 1.31 (CI 1.03-1.67), corrected for age, sex, stage, year of diagnosis and surgical outcome (radical, non-radical or no operation). CONCLUSION: The overall incidence rate of gastric cancer has decreased dramatically in the past 20 years. However, the reduction is largely limited to the intestinal adenocarcinoma sub-group. We conclude that the Laurén classification predicts prognosis in gastric adenocarcinoma with diffuse adenocarcinoma having worse prognosis. KEY WORDS: gastric cancer, Laurén classification, survival, incidence. Correspondence: Halla Sif Olafsdottir, hsolafsdottir@gmail.com.

Loss-of-function variants in ATM confer risk of gastric cancer.

Gastric cancer is a serious health problem worldwide, with particularly high prevalence in eastern Asia. Genome-wide association studies (GWAS) in Asian populations have identified several loci that associate with gastric cancer risk. Here we report a GWAS of gastric cancer in a European population, using information on 2,500 population-based gastric cancer cases and 205,652 controls. We found a new gastric cancer association with loss-of-function mutations in ATM (gene test, P = 8.0 × 10(-12); odds ratio (OR) = 4.74). The combination of the loss-of-function variants p.Gln852*, p.Ser644* and p.Tyr103* (combined minor allele frequency (MAF) = 0.3%) also associates with pancreatic and prostate cancers (OR = 3.81 and 2.18, respectively) and gives an indication of risk of breast and colorectal cancers (OR = 1.82 and 1.97, respectively). Cancers in those carrying loss-of-function ATM mutations are diagnosed at a significantly earlier age than in non-carriers. Our results confirm an association between gastric cancer in Europeans and three loci previously reported in Asians, MUC1, PRKAA1 and PSCA, refine the association signal at PRKAA1 and support a pathogenic role for the tandem repeat identified in MUC1.

[Results of immediate breast reconstructions at Landspítali-The National University Hospital of Iceland, in 2008-2010]. / Tídni og árangur tafarlausra brjóstauppbygginga á Landspítala 2008-2010.

INTRODUCTION: In late 2007, the availability of immediate breast reconstructions increased as a result of the establishment of an oncoplastic breast surgical service at Landspítali-The National University Hospital The aim of this study was to look at the rates and early complications of immediate breast reconstructions in our hospital in 2008-2010 and compare with the results from the UK National Mastectomy and Breast Reconstruction Audit (NMBRA). MATERIAL AND METHODS: This is a retrospective population-based study, including all women who had immediate breast reconstruction at Landspítali in 2008-2010. RESULTS: 319 mastectomies and 157 breast reconstructions were performed. Of these, 98 (62%) were immediate, (mean age 49, 29-69). The immediate breast reconstruction rate was therefore 31%, with a respective 55% for patients 50 years old or younger. In comparison, the rate was 5% in 2000-2005. Immediate reconstructions with an extended autologous latissimus dorsi flap were performed in 25 (26%) cases and implant based reconstructions in the remaining (n=73, 74%). Inpatient complications occurred in 12 (12%) patients and 5 needed reoperation (3 post-operative bleeding, 1 skin necrosis, 1 imminent LD-flap failure). Readmission due to complications after discharge occurred in 14 (14%), while 37 (38%) developed mild complications not requiring readmission. The results were comparable to NMBRA, although the rates of autologous flap reconstructions were significantly higher than in this study (63% vs. 26%). CONCLUSION: As a result of the establishment of an oncoplastic breast surgical service at Landspítali, the rates of immediate breast reconstruction have increased significantly (from 5% to 31%). The complication rates are low and similar to NMBRA.

Discovery of common variants associated with low TSH levels and thyroid cancer risk.

To search for sequence variants conferring risk of nonmedullary thyroid cancer, we focused our analysis on 22 SNPs with a P < 5 × 10(-8) in a genome-wide association study on levels of thyroid stimulating hormone (TSH) in 27,758 Icelanders. Of those, rs965513 has previously been shown to associate with thyroid cancer. The remaining 21 SNPs were genotyped in 561 Icelandic individuals with thyroid cancer (cases) and up to 40,013 controls. Variants suggestively associated with thyroid cancer (P < 0.05) were genotyped in an additional 595 non-Icelandic cases and 2,604 controls. After combining the results, three variants were shown to associate with thyroid cancer: rs966423 on 2q35 (OR = 1.34; P(combined) = 1.3 × 10(-9)), rs2439302 on 8p12 (OR = 1.36; P(combined) = 2.0 × 10(-9)) and rs116909374 on 14q13.3 (OR = 2.09; P(combined) = 4.6 × 10(-11)), a region previously reported to contain an uncorrelated variant conferring risk of thyroid cancer. A strong association (P = 9.1 × 10(-91)) was observed between rs2439302 on 8p12 and expression of NRG1, which encodes the signaling protein neuregulin 1, in blood.