Icelandic Cancer Society

Worldwide, the health-promoting effects of breastfeeding on children and their mothers are indisputable. The frequency and duration of breastfeeding varies greatly internationally but studies on prevalence and influencing factors of breastfeeding in Iceland are scanty and the published ones deal with small groups. The aim of this research is to describe the epidemiology of breastfeeding duration and its influencing factors in Iceland among a large cohort in a whole population over almost one century. This is a historical cohort study, using data from The Cancer Detection Clinic Cohort of The Icelandic Cancer Society, collected retrospectively by questionnaires during the years 1964-2008. The data consisted of mothers´ reported information on breastfeeding of their 81,889 children, 36,537 first-borns and 45,352 younger siblings. The frequency and duration of breastfeeding was calculated and the effects of the following exposure variables were assessed: Maternal age, BMI (N=4950, data collected 1979-2008) and smoking (N=32.087, data collected 1995-2008), the child's year of birth and its order in the sibling group. The children were born in the period of 1917-2008. In the late 1970s, the average duration of breastfeeding began to increase, in all age groups of mothers, increasing rapidly from 3 months to 7-8 months. At about the same time, the breastfeeding duration increased depending on the birth order of the children, younger children were breastfed for longer than their older siblings. Women with normal weight (BMI 18.5 to 24.9) breastfed their babies the longest, while obese women breastfed the shortest. Women with any history of smoking reported shorter duration of breastfeeding than women who had never smoked. The increase in the average duration of breastfeeding in Iceland a few decades ago is in accordance with the information in the World Health Organization's database from European countries 1975-2000, where the Nordic countries and most Northern European countries promoted breastfeeding at a similar time. High BMI and maternal smoking are important variables when studying breastfeeding and this study indicates their negative association with the duration of breastfeeding.

Cancers in the liver, bile duct system, gallbladder as well as metastases of the liver, have poor prognosis. Their treatment is comparable, with surgery being the most widespread, available curative treatment. Surgical treatment is anatomical or non-anatomical resection of the liver where the tumor and the adjacent liver tissue are removed. A list of patients diagnosed with cancer in the liver, bile duct system, gallbladder or metastases of the liver, during the time period 2013-2017, was obtained from the Icelandic Cancer Registry. Additional information was retrieved from medical records and entered into the electronic quality registration forms of Landspítalinn. A comparison was made between Sweden and Iceland. In total 108 patients were diagnosed with primary cancer of the liver, of which 24 (22%) underwent liver surgery. Of 264 diagnosed with liver metastases 38 (14%) underwent surgical treatment. A total of 63% of all reported cases were discussed at a multidisciplinary team meeting in Iceland but 93% in Sweden (p<0.0001). A sum of 29 patients (43%) developed complications within 30 days of surgery. Number of partial liver resections per 100.000 inhabitants were 2-8 in Iceland versus 4-13 in Sweden. The difference was even more apparent in patients with liver metastases. Liver surgeries performed in Iceland seem to be comparable to Sweden in terms of complications and post operative mortality. In Iceland, considerably fewer operations are performed per capita, especially on liver metastases which could be explained by the fact that fewer patients are discussed at multidisciplinary team meetings.

The severity of the COVID‐19 pandemic and subsequent mitigation strategies have varied across the Nordic countries. In a joint Nordic population‐based effort, we compared patterns of new cancer cases and notifications between the Nordic countries during 2020. We used pathology notifications to cancer registries in Denmark, the Faroe Islands, Finland, Iceland, Norway and Sweden to determine monthly numbers of pathology notifications of malignant and in situ tumours from January to December 2020 compared to 2019 (2017‐2019 for Iceland and the Faroe Islands). We compared new cancer cases per month based on unique individuals with pathology notifications. In April and May 2020, the numbers of new malignant cases declined in all Nordic countries, except the Faroe Islands, compared to previous year(s). The largest reduction was observed in Sweden (May: −31.2%, 95% CI −33.9, −28.3), followed by significant declines in Finland, Denmark and Norway, and a nonsignificant decline in Iceland. In Denmark, Norway, Sweden and Finland the reporting rates during the second half of 2020 rose to almost the same level as in 2019. However, in Sweden and Finland, the increase did not compensate for the spring decline (annual reduction −6.2% and −3.6%, respectively). Overall, similar patterns were observed for in situ tumours. The COVID‐19 pandemic led to a decline in rates of new cancer cases in Sweden, Finland, Denmark and Norway, with the most pronounced reduction in Sweden. Possible explanations include the severity of the pandemic, temporary halting of screening activities and changes in healthcare seeking behaviour.

The dynamic growth of the skeleton during childhood and adolescence renders it vulnerable to adverse effects of cancer treatment. The lifetime risk and patterns of skeletal morbidity have not been described in a population-based cohort of childhood cancer survivors. A cohort of 26 334 1-year cancer survivors diagnosed before 20 years of age was identified from the national cancer registries of Denmark, Finland, Iceland and Sweden as well as a cohort of 127 531 age- and sex-matched comparison subjects randomly selected from the national population registries in each country. The two cohorts were linked with data from the national hospital registries and the observed numbers of first-time hospital admissions for adverse skeletal outcomes among childhood cancer survivors were compared to the expected numbers derived from the comparison cohort. In total, 1987 childhood cancer survivors had at least one hospital admission with a skeletal adverse event as discharge diagnosis, yielding a rate ratio (RR) of 1.35 (95% confidence interval, 1.29-1.42). Among the survivors, we observed an increased risk for osteonecrosis with a RR of 25.9 (15.0-44.5), osteoporosis, RR 4.53 (3.28-6.27), fractures, RR 1.27 (1.20-1.34), osteochondropathies, RR 1.57 (1.28-1.92) and osteoarthrosis, RR 1.48 (1.28-1.72). The hospitalization risk for any skeletal adverse event was higher among survivors up to the age of 60 years, but the lifetime pattern was different for each type of skeletal adverse event. Understanding the different lifetime patterns and identification of high-risk groups is crucial for developing strategies to optimize skeletal health in childhood cancer survivors.

The worldwide incidence of cutaneous squamous cell carcinoma (cSCC) is increasing. To evaluate the tumour burden of insitu and invasive cSCC in Iceland, where the population is exposed to limited ultraviolet radiation. This whole-population study used the Icelandic Cancer Registry, which contains records of all insitu and invasive cSCC cases from 1981 to 2017. Incidence of cSCC was evaluated according to age, anatomical location, residence and multiplicity, and trends were assessed using joinpoint analysis. Age-standardized rates (WSR) and age-specific incidence rates per 100000 person-years were calculated, along with cumulative and lifetime risks. Between 1981 and 2017, insitu cSCC WSR increased from 1·2 to 19·1 for men and from 2·0 to 22·3 for women. Invasive cSCC WSR rose from 4·6 to 14 for men and from 0·3 to 13·2 for women. The average number of insitu cSCC lesions was 1·71 per woman and 1·39 per man. Women developed more insitu cSCCs than invasive cSCCs in almost all anatomical locations, whereas men developed more invasive cSCCs, mostly on the head and neck. The rates of insitu cSCC were higher in Reykjavik compared with rural areas. Furthermore, women more commonly developed multiple insitu lesions. For lip cSCCs, invasive lesions occurred more frequently than insitu lesions among both sexes. Joinpoint analysis showed that insitu cSCC in women exhibited the most rapid incidence increase. cSCC has become an increasingly significant public health problem in Iceland. Tanning bed use and travelling abroad may contribute to skin cancer development. Public health efforts are needed to stem the behaviours leading to this rapid rise in cSCC.

Introduction Screening has been the primary reason for the decline in the incidence and mortality of cervical cancer in the Nordic countries since the beginning of screening in the 1960s. Recently, the incidence of cervical cancer has increased in the Nordic countries indicating the need to look closely at possibilities for further improvement in screening. This article provides an overview of cervical cancer screening programmes in the Nordic countries and whether the programmes adhere to international recommendations. Materials and methods Relevant and unambiguous screening recommendations were extracted from applicable literature and classified into legal framework, governance, organisation, and monitoring and evaluation. The up-to-date status of screening programmes and adherence to selected recommendations was gathered from official documentation and co-authors representing cervical cancer screening programmes in all the Nordic countries. Results A total of 168 recommendations were extracted and 54 of them were considered to be unambiguous and relevant. Forty-nine recommendations were included after synthesising similar recommendations. All Nordic countries adhere to recommendations related to legal framework, but adherence was lower with recommendations related to governance and organisation of screening. Monitoring and evaluation are also areas where adherence to recommendations could be improved. Conclusions The Nordic cervical cancer screening programmes have substantially decreased cancer burden despite not fully adhering to many of the recommendations. The presented gaps in adherence suggest that there is room for improvement in the screening programmes. Establishing clearer governance structures would still increase the ability to manage changes such as implementing HPV testing as the primary screening method or modifying the programme when HPV vaccinated cohorts of women enter the target age for screening.

Background: Evidence suggests that among some occupational groups, there is an elevated risk of kidney cancer. This might, however, derive from a difference in smoking habits across occupational groups. The objective of this study was to determine smoking-adjusted occupational variation in the incidence of kidney cancer in Nordic males.Material and Methods: The source population for this study consisted of 7.4 million men from Denmark, Iceland, Finland, Norway, and Sweden. Data on occupation were obtained from national censuses conducted in the years 1960–1990. Data on cancer cases came from national cancer registries. A proxy for the occupation-specific smoking prevalence among all Nordic men was calculated based on the occupation-specific smoking prevalence and lung cancer incidence data for Finnish men. Smoking-adjusted standardized incidence ratio (SIRadj) with 95% confidence intervals (95%CI) were calculated for each occupational group.Results: The highest SIRadj estimates were observed in dentists (1.32, 95%CI 1.06–1.62), journalists (1.20, 95%CI 1.00–1.42), physicians (1.19, 95%CI 1.03–1.36), public safety workers (1.18, 95%CI 1.10–1.26), administrators (1.17, 95%CI 1.13–1.22), military personnel (1.16, 95%CI 1.05–1.28), and religious workers (1.17, 95%CI 1.09–1.26). The lowest SIRadj was observed among forestry workers (0.82, 95%CI 0.76–0.88).Conclusions: Tobacco smoking plays an important role in the occupational variation in the risk of kidney cancer. The smoking-adjusted incidence of kidney cancer was increased in dentists, physicians, journalists, administrators, and public safety workers.

BackgroundBreast Cancer 1 gene (BRCA1) is known to be inactivated in breast tumors by promoter methylation. Tumor cells in patients carrying a germline mutation in BRCA1 are sensitive to cytotoxic drugs that cause DNA double strand breaks. However, very little is known on whether patients with BRCA1 promoter methylated tumors are similarly sensitive to cytotoxic drugs. In this study, we address this by making use of extensive follow-up data on patients treated with cyclophosphamide, methotrexate, and fluorouracil in Iceland between 1976 and 2007.MethodsWe analyzed BRCA1 promoter methylation by pyrosequencing DNA from tumor samples from 1031 patients with primary breast cancer. Of those, 965 were sporadic cases, 61 were BRCA2, and five were BRCA1 germline mutation carriers. All cases were examined with respect to clinicopathological parameters and breast cancer–specific survival in patients treated with cytotoxic drugs. Information on chemotherapy treatment in noncarriers was available for 26 BRCA1 methylated tumors and 857 unmethylated tumors.ResultsBRCA1 was promoter methylated in 29 sporadic tumors or in 3.0% of cases (29 of 965), whereas none of the tumors derived from BRCA germline mutation carriers were promoter methylated. Important to note, patients with BRCA1 promoter methylation receiving chemotherapeutic drug treatment show highly improved breast cancer–specific survival compared with unmethylated controls (hazard ratio = 0.10, 95% confidence interval = 0.01 to 0.75, two-sided P = .02).ConclusionsBRCA1 promoter methylation is predictive of improved disease outcome in patients receiving cyclophosphamide, methotrexate, and fluorouracil drug treatment. Our results support the use of markers indicative of “BRCAness” in sporadic breast cancers to identify patients that are likely to benefit from the use of DNA-damaging agents.

As obesity and type 2 diabetes (T2D) have been increasing worldwide, we investigated their association with breast cancer incidence in the Reykjavik Study. During 1968-1996, approximately 10,000 women (mean age = 53 ± 9years) completed questionnaires and donated blood samples. T2D status was classified according to self-report (n = 140) and glucose levels (n = 154) at cohort entry. A linkage with the Icelandic Cancer Registry provided breast cancer incidence through 2015. Cox regression with age as time metric and adjusted for known confounders was applied to obtain hazard ratios (HR) and 95% confidence intervals (CI). Of 9,606 participants, 294 (3.1%) were classified as T2D cases at cohort entry while 728 (7.8%) women were diagnosed with breast cancer during 28.4 ± 11.6years of follow-up. No significant association of T2D (HR 0.95; 95% CI 0.56-1.53) with breast cancer incidence was detected except among the small number of women with advanced breast cancer (HR 3.30; 95% CI 1.13-9.62). Breast cancer incidence was elevated among overweight/obese women without (HR 1.18; 95% CI 1.01-1.37) and with T2D (HR 1.35; 95% CI 0.79-2.31). Height also predicted higher breast cancer incidence (HR 1.03; 95% CI 1.02-1.05). All findings were confirmed in women of the AGES-Reykjavik sub-cohort (n = 3,103) who returned for an exam during 2002-2006. With a 10% T2D prevalence and 93 incident breast cancer cases, the HR for T2D was 1.18 (95% CI 0.62-2.27). These findings in a population with low T2D incidence suggest that the presence of T2D does not confer additional breast cancer risk and confirm the importance of height and excess body weight as breast cancer risk factors.