Lotti Barlow

The completeness of the Swedish Cancer Register - a sample survey for year 1998

Introduction. The Swedish Cancer Register (SCR) is used extensively for monitoring cancer incidence and survival and for research purposes. Completeness and reliability of cancer registration are thus of great importance for all types of use of the cancer register. The aim of the study was to estimate the overall coverage of malignant cancer cases in 1998 and to reveal possible reasons behind non-reporting. Methods. We selected all malignant cancer cases in the Hospital Discharge Register (HDR) from 1998 and compared these records to those reported to the SCR. There were 43 761 discharges for 42 010 individuals of whom 3 429 individuals were not recorded in the SCR. From these 3 429 records we randomly selected 202 patients for review of their medical records to determine whether they should have been registered on the SCR as incident cases in 1998. Results. About half of the 202 cases (93 malignant and 8 benign) should have been reported, which translates into an additional 1 579 malignant cases (95% CI 1 349–1 808), or 3.7% of the cases reported in 1998. The crude incidence rate for males and females combined would increase from 493 per 100 000 to 511 (95% CI 508–514) if these cases were taken into account. Conclusion. The overall completeness of the SCR is high and comparable to other high quality registers in Northern Europe. For most uses in epidemiological or public health surveillance, the underreporting will be without major impact. However, for specific research questions our findings have implications, as the degree of underreporting is site specific, increases with age, and does not seem to be random, as diagnoses without histology or cytology verification are overrepresented. An annual comparison of the SCR against the HDR could point to hospitals, geographic areas or specific diagnoses where organizational and administrative changes should be introduced to improve reporting.

Decreasing Late Mortality Among Five-Year Survivors of Cancer in Childhood and Adolescence: A Population-Based Study in the Nordic Countries

PURPOSE To assess the risk of death in patients who survive more than 5 years after diagnosis of childhood cancer and to evaluate causes of death in fatal cases. PATIENTS AND METHODS This was a population-based study in the five Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) using data of the nationwide cancer registries and the cause-of-death registries. The study cohort included 13,711 patients who were diagnosed with cancer before the age of 20 years between 1960 and 1989 and who survived at least 5 years from diagnosis. By December 31, 1995, 1,422 patients had died, and death certificates were assessed in 1,402. Standardized mortality ratios (SMRs) for validated causes of death were calculated based on 156,046 patient-years at risk. RESULTS The overall SMR was 10.8 (95% confidence interval [CI], 10.3 to 11.5), mainly due to high excess mortality from the primary cancer. SMR for second cancer was 4.9 (95% CI, 3.9 to 5.9) and was 3.1 (95% CI, 2.8 to 3.5) for noncancer death. The pattern of causes of death varied markedly between different groups of primary cancer diagnoses and was highly dependent on time passed since diagnosis. Overall late mortality was significantly lower in patients treated during the most recent period of time, 1980 to 1989, compared with those treated from 1960 to 1979 (hazard ratio, 0.61; 95% CI, 0.54 to 0.70), and there was no increase in rates of death due to cancer treatment. CONCLUSION Long-term survivors of childhood cancer had an increased mortality rate, mainly dying from primary cancers. However, modern treatments have reduced late cancer mortality without increasing the rate of therapy-related deaths.

Cancer Survival in Sweden 1960–1998 Developments Across Four Decades

This paper summarizes a comprehensive study of cancer survival in Sweden from 1960 to 1998. A total of 1 021 421 persons and 40 different cancer sites were included in the analyses. The main outcome measure is the relative survival rate (RSR) for different sites and follow-up times after diagnosis. The 10-year RSR for all sites combined has increased steadily—from 26.6% among men and 41.8% among women in the 1960s, to 44.6% (men) and 57.6% (women) in the 1990s. The expectation of life for a person diagnosed with cancer today is about 7 years longer than that of one diagnosed during the mid-1960s. About 3 years are gained due to changes in the relative distribution of various cancer types and about 4 years due to improved relative survival. During the 1990s substantial survival improvements were observed not only for uncommon types, such as testicular cancer, Hodgkins lymphoma and some other haematologic malignancies, but also for cancer of the rectum, kidney and malignant melanoma. Survival for breast and cervical cancer also improved during the 1990s, but not that for pancreatic, liver or lung cancer.

Multiple Primary Malignant Tumors in a National Cancer Registry: Reliability of Reporting

During the years 1958-1988, 808,522 individuals were registered in the Swedish national population-based cancer register with a total of 933,900 primary malignant tumors. Roughly 11% of the tumors reported to the Swedish Cancer Registry in 1988 were found in persons earlier registered for another primary malignancy. One hundred of the individuals registered with multiple primary malignant tumors were randomly selected for a study of the reliability of reporting of multiple malignancies. Medical records and when necessary histopathological slides and other relevant diagnostic material for each malignancy were collected and the diagnoses reevaluated. Three persons had to be excluded; thus 97 cases with 209 reported malignancies were analysed. Of these, 94% of the first, 98% of the second and 79% of the third malignancy were accepted. Twelve of the reported tumors were not accepted as malignant, five were benign or cancer in situ, five were incorrectly reported as new primaries and two were a second incorrect registration of a previously registered malignancy. All 97 persons had at least one malignant tumor, in 90% of the persons all reported diagnoses were accepted and 93% had multiple primary malignancies. The results of this quality control study indicate that suitable data are available in the Swedish Cancer Registry for investigations related to the occurrence of multiple primary malignancies in a large unselected population. The Swedish Cancer Registry, to which all newly diagnosed malignancies by law have to be reported, comprise today close to one million individuals with registered malignancies.

Cancer in siblings of children with cancer in the Nordic countries: a population-based cohort study

BACKGROUND In some rare inherited disorders such as Li-Fraumeni syndrome, relatives of children with cancer are at increased risk of cancer. We aimed to assess relations between childhood cancer and sibling risk, and evaluate the influence of recessive conditions in cancer causation. METHODS We did a population-based cohort study in the Nordic countries of 42277 siblings of 25605 children with cancer. Children with cancer were identified from records in the five Nordic cancer registries, and their siblings from nationwide population registries. Cancers in siblings were documented through record linkage with cancer registries and compared with national incidence rates. We also assessed cancer incidence in parents to identify familial cancer syndromes. FINDINGS 284.2 cancers were expected in siblings, whereas 353 were diagnosed (standardised incidence ratio 1.24 95% CI 1.12-1.38). Risk ratios for siblings were highest in the first decade of life (2.59, 1.89-3.46). We excluded 56 families with genetic syndromes linked to cancer, which reduced this ratio from 1.7 to 1.0 (0.7-1.3) for siblings younger than 20 years, and from 1.3 to 1.0 (0.8-1.3) for those aged 20-29 years. We found no new patterns of familial cancer that indicated inherited susceptibility, or evidence that recessive conditions might contribute to cancers not explained by syndromes. 40% of cancers in siblings that occurred before age 20 years could be attributed to known genetic factors, whereas 60% remained unexplained. INTERPRETATION Apart from rare cancer syndromes, paediatric cancer is not an indicator of increased cancer risk in siblings.

Late mortality among five-year survivors of cancer in childhood and adolescence.

The present study was aimed at assessing differences between the Nordic countries, if any, in late mortality among five-year survivors of childhood cancer. All cases diagnosed before the age of 20 years, between 1960 and 1989, were collected from all Nordic cancer registries. In total, 13 689 patients were identified as five-year survivors and during the extended follow-up 12.3% of them died. Mortality was analysed by decade of diagnosis, for all sites, and for leukaemia, Hodgkins lymphoma, and central nervous system tumours separately. Analyses were done within a Cox proportional hazards regression framework with adjustments made for gender and age at diagnosis. Hazard ratios were calculated in relation to a weighted Nordic mean based on the proportion of five-year survivors in each country. Overall late mortality was significantly higher in Denmark and Finland than in Norway and Sweden. This could not be explained by inverse differences in five-year survival. The differences diminished over time and had disappeared in the last period. The pattern was similar for both genders. The disappearance of the differences was most probably the effect of a closer collaboration between Nordic paediatric oncologists with development and implementation of common protocols for treatment of childhood cancers in all countries.

Risk for endometrial cancer following breast cancer: A prospective study in Sweden

The risk for endometrial cancer among women with breast cancer might increase following use of tamoxifen, recently classified as a carcinogen of the human endometrium. However, the strength of the association remains uncertain and it is unknown whether use of this drug - widely prescribed in Sweden since the mid-1980s - has had any measurable effect at the population level. We analyzed all cases of breast cancer (n = 131,614) detected in the nationwide Swedish Cancer Registry in 1958-93. Incident cases of endometrial cancer during follow-up were identified also through the Cancer Registry. Standardized incidence ratios (SIR) and their 95 percent confidence intervals(CI) were computed by use of nationwide rates of endometrial cancer, adjusted for age and calendar year. During follow-up of up to 35 years of the breast cancer cohort, 803 incident endometrial cancers were identified, yielding an overall SIR of 1.58 (CI = 1.47-1.70). In univariate analyses, there was no increase in SIR in recent years. However, the excess risk increased linearly with increasing age at breast cancer diagnosis (P trend < 0.0001) and decreased markedly with longer follow-up (P trend < 0.0001). A multivariate regression analysis, with adjustment for age and year of follow-up, revealed no increased risk for subsequent endometrial cancer among breast cancer cases diagnosed more recently (P trend = 0.19); compared with the period 1958-63,the risk estimate in the last time period (1989-93) was 0.72 (CI =0.51-1.01). We conclude that the risk for endometrial cancer following breast cancer has not increased over time in Sweden.

Chapter 3. Major Health Problems

1Gudrun Persson (Mental illness, Urinary incontinence, Disorders of the Locomotive System, Allergy and asthma and Dental health), Centre for Epidemiology, National Board of Health and Welfare, SE-106 30 Stockholm, Sweden. Tel:+46 8 5555 3013, Fax:+46 8 5555 3327. E-mail: gudrun.persson@sos.se, 2Lotti Barlow (Tumour Diseases), Centre for Epidemiology, National Board of Health and Welfare, SE-106 30 Stockholm, Sweden. Tel:+46 8 5555 3443, Fax:+46 8 5555 3327. E-mail: lotti.barlow@sos.se, 3Anders Karlsson and Anders AE berg (Injuries), Centre for Epidemiology, National Board of Health and Welfare, SE-106 30 Stockholm, Sweden. Tel:+46 8 5555 3000, Fax:+46 8 5555 3327. E-mail: anders.aberg@sos.se, 4MaE ns Rosen (Cardiovascular Diseases and Diabetes), Centre for Epidemiology, National Board of Health and Welfare, SE-106 30 Stockholm, Sweden. Tel:+46 8 5555 3096, Fax:+46 8 5555 3327. E-mail: mans.rosen@sos.se, 5Claes-Goran Stefansson (Mental illness), Social Welfare Department, National Board of Health and Welfare, SE-106 30 Stockholm, Sweden. Tel:+46 8 5555 3042. E-mail: claes-goran.stefansson@sos.se, 6Tores Theorell (Stress –a DiseaseRisk), National Institute for Psychosocial Factors and Health (IPM), Box 230, SE-171 77 Stockholm, Sweden. Tel+46 8 728 64 00. E-mail: tores.theorell@ipm.ki.se, 7Peet Tull (Infectious diseases), Infectious diseases prevention, Supervision Department, National Board of Health and Welfare, SE-106 30 Stockholm, Sweden. Tel:+46 8 5555 3000, E-mail: peet.tull@sos.se

Chapter 5.4: Major public health problems — cancer

N Cancer is the second most common cause of death for both genders after cardiovascular disease. N Cancer predominantly afflicts older people. Two of three cases occur after age 65. N The probability for a man to be diagnosed with cancer before age 75 is about 30% and for a woman almost 27%. N Close to 25% of all cancer is caused by tobacco smoking, the single known factor that causes most cancer cases. N The incidence of cancer in Sweden increased by 1.1% per year among men and by 0.5% per year among women (age-standardized figures) from 1994 to 2003. N Just over half of those diagnosed with cancer today are expected to live as long as their coevals. Early detection and improved treatment, contribute to increased survival. N Breast cancer is the most common cancer form among women, representing about 30% of all female cancer. During the past 10 years the incidence of breast cancer has increased by 1.5% annually. Mortality, however, is not increasing. N Prostate cancer represents about 35% of all cancers in men. The incidence has increased by an average of 4% annually for the past 10 years, chiefly due to early detection. However, the increased incidence is not accompanied by increased mortality. N During the past 10 years, the incidence of prostate cancer and skin cancer have increased among men, while the incidence of lung cancer has declined. Among women, breast, lung and skin cancer are increasing. Cancer prevalence varies between countries and continents

A DECLINE IN THE LUNG CANCER INCIDENCE AMONGST MEN IN SWEDISH CITIES

A statistically-significant (p < 0.01) decrease in the incidence of lung cancer has been observed amongst men in larger Swedish cities, but not in the country as a whole. The decrease is foremostly attributable to changes within the group of older men (i.e., > 65 years). The investigation is based on the Swedish Cancer Registry and covers the period 1975-1989.