[Cancer registration in Iceland for 70 years - incidence, mortality and survival].

INTRODUCTION: The Icelandic Cancer Registry (ICR) was founded seventy years ago by the Icelandic Cancer Society. In 2007 the ICR became one of the health registers of the Directorate of Health. In this paper we present cancer incidence, mortality, and survival in Iceland over 70 years. MATERIAL AND METHODS: The ICR receives information on cancer diagnoses from histopathological laboratories, the Hospital Discharge Registry and the Cause of Death Registry. Iceland participates in the Nordic cancer database NORDCAN. Because of the small population size, random variation in numbers is very prominent. Therefore, data from ICR are published as five-year averages. RESULTS: For all malignancies combined, age-standardized incidence (ASI) in men rose steadily until around 15 years ago when a decline started. This is in line with prostate- and lung cancer incidence trends. In women, the ASI was lower than in men, but it is still on the rise despite declining lung cancer incidence. ASI for breast cancer, the most common cancer in women, is increasing. Simultaneously, cancer mortality for both sexes has declined in recent years and cancer survival is improving. CONCLUSIONS: Population-based cancer registration for over 70 years makes it possible to monitor the epidemiology of cancer in Iceland and compare with other countries. The changes in trends in ASI are in line with changes of cancer risk factors and diagnostic policy. The decline in cancer mortality and improvement in survival reflects advances in cancer treatment as well as effects of early detection and prevention.

Data quality at the Icelandic Cancer Registry: comparability, validity, timeliness and completeness.

INTRODUCTION: The nationwide Icelandic Cancer Registry (ICR) was established in 1954 and has been extensively used for research from the outset although formal quality assessment of the registry database has not previously been undertaken. In this paper we report the first formal evaluation of the comparability, validity, timeliness and completeness of the ICR. MATERIAL AND METHODS: Data from the ICR for the period 1955-2009 (41 994 cancer diagnoses) were used, applying established quantitative and semi-quantitative methods. In order to evaluate the completeness of the ICR, record linkage was performed between the ICR and the population-based Hospital Discharge Registry to identify potential missing cases for tumour diagnoses in 2000 and 2001. RESULTS: The registration is in accordance with internationally accepted standards. It has high validity, but random variation in rates is prominent in this small population. Record linkage with the Hospital Discharge Registry revealed that in addition to the 2459 cancers registered in 2000-2001, 21 cases were missing, indicating 99.15% completeness. Tumours of the central nervous system constituted 71%, and haematological malignancies 19% of these missing entries. DISCUSSION: The ICR has high completeness, validity and timeliness and is comparable to the cancer registries of the other Nordic Countries. As cancer registries have many important roles, it is of great importance that their data are at all times as complete and valid as possible. Thus the ICR aims to constantly improve and update the data gathering process.

Population-based service mammography screening: the Icelandic experience.

OBJECTIVE: This study analyzes the efficacy of the Icelandic population-based service mammography screening. MATERIAL AND METHODS: Women aged 40-69 were invited for screening at 2-year intervals starting in November 1987. The study evaluates: (A) attendance and other screened performance parameters during 1998-2010; (B) trends in age-standardized and age-specific incidence rates during 1969-2010 and mortality rates during 1969-2010; and (C) distribution of risk factors and disease specific death rates according to mode of detection. RESULTS: (A) In the age group of 40-69, the average 2-year attendance was 62%, recall rate was 4.1%, needle biopsy rate was 1.3%, surgery rate was 0.6%, invasive cancer rate was 0.4%, and ductal carcinoma in situ (DCIS) rate was 0.06%. (B) The linear incidence trend after the start of screening decreased significantly in the age group 40-49, increased significantly in the age group 50-69, but decreased non-significantly in the age group 70-79. The decreased age-specific incidence in the 70-79 age group was, however, greater than the increased age-specific incidence at the ages 50-69. The mortality rate decreased 41% for all age groups and the linear mortality trend decreased significantly at ages 40-49, 50-69, and 70-79. In the age group 40-74 years, the age-specific mortality decreased by 6.9 cases per 2000 during a 10-year period. (C) Screen-detected women had significantly smaller tumors, more favorable tumor grade, fewer axillary metastases and, after correction for other risk factors, the likelihood of dying from cancer decreased 54% (hazard ratio: 0.46; 95% confidence interval: 0.31-0.69) for these patients compared to cases of nonparticipators. CONCLUSION: The study results confirm acceptable rates of recalls and referrals for further diagnosis and treatment, and significantly decreased breast cancer mortality rate after starting screening.

Prostate cancer progression and survival in BRCA2 mutation carriers.

BACKGROUND: Mutations in the BRCA2 gene are associated with an increased risk of prostate cancer, but it is not known whether they are associated with progression of the disease. We compared prostate cancer-specific survival, disease stage, and tumor grade between prostate cancer patients carrying the Icelandic BRCA2 999del5 founder mutation and noncarriers. METHODS: Using population-based registries, we identified all 596 prostate cancer patients who were diagnosed in Iceland during 1955 through 2004 among 29603 male relatives of unselected breast cancer probands. BRCA2 mutation status could be determined for 527 patients (88.4%). Stage and grade were abstracted from original records, blindly with respect to mutation status, for a subgroup of 89 patients that included all mutation carriers and, for each carrier, two control patients without the BRCA2 999del5 mutation who were matched to the carrier on years of diagnosis and birth. Hazard ratios (HRs) and 95% confidence intervals (CIs) for prostate cancer-specific survival were estimated using multivariable regression models. All statistical tests were two-sided. RESULTS: The mutation was carried by 30 patients (5.7%). Compared with noncarriers, BRCA2 999del5 mutation carriers had a lower mean age at diagnosis (69.0 years versus 74.0 years; P = .002), more advanced tumor stage (stages 3 or 4, 79.3% versus 38.6%; P < .001), higher tumor grade (grades G3-4, 84.0% versus 52.7%, P = .007), and shorter median survival time (2.1 years, 95% CI = 1.4 to 3.6 years, versus 12.4 years, 95% CI = 9.9 to 19.7 years). Carrying the BRCA2 999del5 mutation was also associated with an increased risk of dying from prostate cancer (adjusting for year of diagnosis and birth, HR = 3.42, 95% CI = 2.12 to 5.51); the association remained after adjustment for stage and grade (HR = 2.35, 95% CI = 1.08 to 5.11). The prognosis of BRCA2 999del5 mutation carriers was not associated with period of diagnosis or with relatedness to breast cancer probands. CONCLUSIONS: The Icelandic BRCA2 999del5 founder mutation was strongly associated with rapidly progressing lethal prostate cancer.