Biomedical subjects
Publications and source records attributed to E Pukkala.
A total of 10935 women with visual impairment were identified from the Finnish Register of Visual Impairment and followed up for cancer through the Finnish Cancer Registry for years 1983-1996. Breast cancer risk decreased by degree of visual impairment (P for trend 0.04) which suggests a dose-response relationship between visible light and breast cancer risk.
It has been suggested that trioxsalen bath and ultraviolet (UV) A (PUVA) is associated with a very low or no risk of non-melanoma skin cancer, but the numbers of patients in individual studies have been limited. In order to attain statistically relevant information about the cancer risk associated with trioxsalen bath PUVA, two follow-up studies were combined and the joined cancer incidence was analysed among 944 Swedish and Finnish patients with psoriasis. The mean follow-up time for skin cancer was 14.7 years. Standardized incidence ratios (SIR) were calculated as a ratio of observed and expected numbers of cases. The expected numbers of cases were based on the national cancer incidence rates in the respective countries. There was no excess of squamous cell skin carcinoma [SIR 1.1, 95% confidence interval (CI) 0.2-3.2] or malignant melanoma (SIR 0.9, 95% CI 0.1-3.2) in the combined cohort. Basal cell skin carcinoma was not studied. The incidence of all non-cutaneous cancers was not increased (SIR 1.1, 95% CI 0.8-1.4). A threefold excess risk of squamous cell skin carcinoma after trioxsalen bath PUVA could therefore be excluded, which is a markedly lower risk than that associated with oral 8-methoxypsoralen PUVA. The result needs to be confirmed in a future follow-up, however, as the number of patients with high PUVA exposures was low.
The effects of primary site, sex, age, stage and histological type on cancer patient survival were analysed on the basis of the population-based material of the Finnish Cancer Registry from 1985 to 1994. In addition, trends in survival were constructed for the period 1955-1994. Detailed site-specific data are published as Supplement 12 to Vol. 38 of Acta Oncologica. Within a given site, the survival differences by gender were not large. However, because of different site distributions, the average prognosis for female patients, all sites taken together, was superior to that of males: the 5-year relative survival rates (RSR) were 58% and 43%, respectively. In general, older patients had a poorer outcome compared with younger patients (partly because of different stage and histology distributions). Stage was a strong determinant of patient survival. In some cancers with a poor average prognosis the 5-year RSR for localized tumours was reasonable, e.g. 61% for stomach cancer, males, 34% for gallbladder cancer, females, and 29% for lung cancer, males. Most of the survival rates clearly increased over time. In addition to improvements in cancer treatment, changes over time in several other factors affect the trends, such as changes in the stage distribution (early diagnosis as a result of health education, improved diagnostic methods, screening, etc.) and in the composition of the patient material because of changing definitions of cancer (e.g. papilloma versus papillary carcinoma of the bladder, occult carcinoma of the thyroid, and early prostate cancer). The large Cancer Registry material (466,000 patients) enabled accurate estimates of the survival rates of cancer patients in Finland. These rates reflect the effectiveness of the healthcare system as a whole and are useful for planning and evaluation purposes. However, the estimated survival rates are based on grouped data, and cannot be directly applied for predicting the prognoses of individual patients, although they can be used as guidelines.
A population-based descriptive study was conducted to describe incidence and survival of cancer of the mobile tongue in Finland between 1953 and 1994. The study included 1504 patients, drawn from the Finnish Cancer Registry, with first primary mobile tongue cancer diagnosed between 1953 and 1994. Incidence and relative survival were determined. The age-standardized overall incidence rate was 0.6 per 100000 years in 1953-1994. At the time of diagnosis 78% of the patients had either localized or regional disease. The age-standardized incidence rate decreased after the mid-1960s, but increased in the 1990s. The 5-year relative survival rate increased gradually from 40% in 1953 1959 to 58% in 1988-1994. Disease stage at the time of the diagnosis strongly affected the survival rate. Survival increased especially in regional disease. Cancer of the mobile tongue is increasing in Finland, but survival has increased particularly in regional disease, probably because of improved treatment. Early diagnosis is emphasized for a good prognosis.
INTRODUCTION: The study of survival of cancer patients is essential for monitoring the effectiveness of cancer control. The previous monograph describing cancer patient survival in Finland was published by the Finnish Cancer Registry in 1981 and covered patients diagnosed in 1953-1974. This new supplement assesses cancer patient survival up to the year 1995. MATERIAL AND METHODS: The study includes over 560000 tumours registered at the Finnish Cancer Registry with a date of diagnosis between 1955 and 1994. Patients were followed up to the end of 1995. Trends in relative survival rates are studied over four 10-year diagnostic periods from 1955 to 1994. In addition, detailed results are presented for patients diagnosed during 1985-1994, including relative survival rates tabulated by stage, sex, and age. Additional sections describe differences in cancer patient survival according to social class and region of residence and a comparison of cancer patient survival in Finland to other European countries. RESULTS: Patient survival improved over time for almost all anatomical sites. The main exception is in cancer of the cervix uteri, where patient survival has decreased slightly from 1965-1974 to 1985-1994 due to the selective prevention of less aggressive tumours through cytologic screening. Very few differences in patient survival are observed between males and females. A substantial improvement in survival can be seen for childhood cancers. CONCLUSION: The increasing survival rates reflect improvements that have taken place in various areas of cancer control, from health education and early diagnosis to treatment and aftercare. This study provides valuable reference information for both clinicians and health administrators, as well as a baseline for more detailed studies of patient survival for individual anatomical sites.
OBJECTIVE: To evaluate whether five years is an appropriate screening interval for cervical cancer for the improvement of public health. SETTING: Finland. METHODS: 45,572 women with a cytological class I smear attending the mass screening programme organised every five years in Finland during 1971 to 1976 and followed up until the end of 1994. The data from the Nationwide Mass Screening Registry were linked to the Finnish Cancer Registry. Standardised incidence ratios of preinvasive and invasive cervical cancer with 95% confidence intervals (CI) were estimated, with rates for the total Finnish population as reference. RESULTS: The standardised incidence ratio estimates were low initially after screening and then gradually increased up to the time of the next smear five years later. This pattern was repeated after each screening. The risk was persistently low for invasive cervical cancer even after 10 years of follow up, whereas the low risk for preinvasive lesions was of a shorter duration. The low risk associated with a negative smear became even lower with advancing age. CONCLUSIONS: Women who attend organised screening programmes and have a negative smear have a low risk of cervical cancer for over 10 years. Also, the relative risk of a preinvasive lesion after an initial negative smear is decreased for more than five years. Therefore, the five year screening interval in Finland is appropriate and effective in reducing the risk of invasive cervical cancer.
OBJECTIVE: To propose principles of design and measures of effect for cancer screening as a public health policy. MATERIAL: Finnish routine screening programme with mammography. DESIGN: Evaluation of mortality from breast cancer by before-after time trends among Finnish women, by geographical (by municipalities) comparisons, and by intention to screen at an individual level with individual controls who were cluster randomised and matched for age. OUTCOME MEASURES: Standardised mortality ratios (SMRs) from breast cancer (total), SMRs from breast cancers diagnosed during the screening programme (refined), deaths prevented, prolongation of life for each breast cancer detected, for each death prevented, for each compliant woman, for each screen, and for each invitation. Relative prolongation of life--that is, time gained versus time spent. RESULTS: SMRs only at an individual level with deaths from cancers diagnosed during the screening programme and individually selected controls showed 24% protection, whereas the other SMR measures were too crude or biased because of dilution and selection. Prolongation of life varied from 15 years for each death prevented to two days for each woman screened, with approximation for the prolongation relative to time spent of 3 to 1. CONCLUSIONS: A public health policy should be introduced gradually. Those not covered immediately by the policy serve as controls and they should be randomly allocated. The most relevant outcome measure is prolongation of life, and for public health purposes it should be given per unit of intervention, such as screen or invitation, and also related to the time spent for the intervention. Such gains are often small in a Western society, which implies that medicine, including research, should focus more on other aspects of life than length.
We assessed the levels of arsenic in drilled wells in Finland and studied the association of arsenic exposure with the risk of bladder and kidney cancers. The study persons were selected from a register-based cohort of all Finns who had lived at an address outside the municipal drinking-water system during 1967-1980 (n = 144,627). The final study population consisted of 61 bladder cancer cases and 49 kidney cancer cases diagnosed between 1981 and 1995, as well as an age- and sex-balanced random sample of 275 subjects (reference cohort). Water samples were obtained from the wells used by the study population at least during 1967-1980. The total arsenic concentrations in the wells of the reference cohort were low (median = 0.1 microg/L; maximum = 64 microg/L), and 1% exceeded 10 microg/L. Arsenic exposure was estimated as arsenic concentration in the well, daily dose, and cumulative dose of arsenic. None of the exposure indicators was statistically significantly associated with the risk of kidney cancer. Bladder cancer tended to be associated with arsenic concentration and daily dose during the third to ninth years prior to the cancer diagnosis; the risk ratios for arsenic concentration categories 0.1-0.5 and [Greater/equal to] 0.5 microg/L relative to the category with < 0.1 microg/L were 1.53 [95% confidence interval (CI), 0.75-3.09] and 2.44 (CI, 1.11-5.37), respectively. In spite of very low exposure levels, we found some evidence of an association between arsenic and bladder cancer risk. More studies are needed to confirm the possible association between arsenic and bladder cancer risk at such low exposure levels.
A nationwide, computer-based survey of all total joint arthroplasties performed in Finland has been carried out since January 1980. From these records, a cohort of 9,444 patients, with 51,756 person-years, after primary operation with a total polyethylene-on-metal knee arthroplasty (TKA) was followed up for cancer through the Finnish Cancer Register up to December 31, 1996. During the follow-up, 706 cancers were observed. The expected number, based on national rates, was 719; therefore, the standardized incidence ratio (SIR) for all cancers was 0.98. The SIRs for non-Hodgkin's lymphoma (1.40), Hodgkin's disease (1.24) and multiple myeloma (1.54) were increased, but only that of non-Hodgkin's lymphoma was statistically significant 3-10 years after the operation. The numbers of observed cases of prostate cancer exceeded that of expected, with a SIR value of 1.49. A low SIR of lung cancer was observed among men, especially during the first 3 years (0.61), but not in women. The SIR for colon cancer was below unity in women only (SIR 0.70). The SIR for cancer of the urinary organs was close to unity (0.97). SIR relating to soft tissue and bone cancer did not differ significantly from unity, and none of the 6 sarcomas was observed at the site of a prosthesis. The overall cancer risk after TKA done for primary osteoarthrosis seems not to be increased. The increases in lymphoma and prostate cancer risk, however, are observations that could be related to TKA and justify further follow-up of the cohort.
This population-based study investigated the occurrence of breast cancer over a 20-year period in a cohort of monozygotic (MZ) and dizygotic (DZ) twins in Finland. Altogether, 13,176 female twins of known zygosity who were living in Finland at the end of 1975 were identified from the Finnish Twin Cohort Study and followed-up for cancer through the Finnish Cancer Registry for the years 1976-1995. Standardized incidence ratios (SIRs) were calculated, based on national cancer incidence rates. The relative risk of breast cancer for MZ twins compared to DZ twins was decreased [SIR(MZ)/SIR(DZ) ratio = 0.78; 95% confidence interval (CI), 0.58-1.0]; the decreased risk for MZ twins (SIR = 0.76; 95% CI, 0.58-1.0) accounted for this result, whereas the risk for DZ twins did not differ from the general population risk (SIR = 0.98; 95% CI, 0.84-1.1). There was no risk decrease among MZ twins in other cancers related to reproductive behavior; i.e., number of children and age at first birth seem not to explain the decreased risk of breast cancer. Our results, which are in line with earlier studies on the same topic, suggest that prenatal influences or postnatal behavioral factors may protect MZ female twins from breast cancer.
This report presents 20 years' of cancer incidence data by occupational group for the Nordic populations. The study covers the 10 million people aged 25-64 years at the time of the 1970 censuses in Denmark, Finland, Norway, and Sweden, and the 1 million incident cancer cases diagnosed among these people during the subsequent 20 years. The project was undertaken as a cohort study with linkage of individual records based on the personal identification numbers used in all the Nordic countries. In the 1970 censuses, information on occupation for each economically active member of the household was provided in free text in self-administered questionnaires. The data were centrally coded and computerized in the statistical offices. Norway, Sweden, and Finland used the Nordic Classification of Occupations, while Denmark used a national coding scheme. However, all the data could be reclassified into 53 occupational groups and 1 group of economically inactive persons. Person-years at risk were accumulated from 1 January 1971 until the date of emigration, date of death or 31 December 1987 in Denmark, 1989 in Sweden, 1990 in Finland, and 1991 in Norway. The 4 countries all had nationwide registration of incident cancer cases during the entire study period. All incident cancer cases during the individual risk periods were included in the analysis. Despite minor differences between the countries, the International Classification of Diseases, 7th revision, formed the core basis for the diagnostic coding in all 4 countries. For the present study the incident cancer cases have been classified into 35 broad diagnostic groups. The observed number of cancer cases in each group of persons defined by country, gender, and occupation was compared with the expected number calculated from the age-, gender-, and period-specific person-years and the incidence rates for the national population. The result has been presented as a standardized incidence ratio (SIR), defined as the observed number of cases divided by the expected number and multiplied by 100. In the tables of this report, all the SIR values for which the upper limit of the 95% confidence interval is below 100 are printed in green and all those for which the lower limit of the confidence interval is above 100 are printed in red. For all cancers combined, the study showed a wide variation among the men, from an SIR of 79 for farmers to 159 for waiters. The occupations with the highest SIR values also included seamen and workers producing beverages and tobacco. Among the women the SIR values varied from 83 for gardeners to 129 for tobacco workers. Low SIR values were found for farmers and teachers. Outdoor workers such as fishermen and gardeners had the highest risk of lip cancer, while the lowest risk was found among indoor workers such as physicians and artistic workers. Almost all pleural cancers are associated with asbestos exposure. Accordingly, plumbers, welders, mechanics, and seamen were the occupations with the highest risk. There was also an excess risk of pleural cancer in the occupational group of technical, chemical, physical, and biological workers, including, among others, engineers and chemists potentially exposed to asbestos. The wood workers included in the present study had the highest risk of nasal cancer. Most studies of nasal cancer have shown increased risks associated with exposure to wood dust, both for those in furniture making and for those exposed exclusively to soft wood. Nickel refinery workers are also known for their high risk of nasal cancer. In the present study they were included in the occupational group of smelting workers. Lung cancer was the most frequent cancer among men in the present study. Tobacco smoking is the major risk factor for this disease, but occupational exposures also play an important role. Waiters and tobacco workers had the highest risk of lung cancer. Miners and quarry workers also had a high risk of lung cancer, which may be related to
The detection of mutagenic and carcinogenic chlorination by-products in chlorinated drinking water has raised concern in many countries over the potential health effects of long-term exposure to these products. The relation between estimated exposure to historical drinking water mutagenicity and cancer was studied in Finland by using a population-based case-control study comprising 732 bladder cancer cases, 703 kidney cancer cases, and 914 controls. The cases were obtained from the nationwide Finnish Cancer Registry for the years 1991-1992. The controls, frequency matched by age and sex, were randomly selected from the national population registry. Information on past drinking water sources and confounding factors was acquired through a questionnaire. Historical exposure to drinking water mutagenicity was estimated by using information on past residence, past water source, and historical data on water quality and treatment. Odds ratios were calculated for an increase of 3,000 net revertants per liter (net rev/liter) in average exposure from 1950 to 1987, adjusting for age, sex, socioeconomic status, and smoking in logistic regression models. A small, statistically significant, exposure-related excess risk was found for kidney cancer for men (odds ratio = 1.49, 95 percent confidence interval (CI) 1.05-2.13) for 3,000 net rev/liter exposure level. For women, the association remained nonsignificant, with a lower odds ratio of 1.08 (95% CI 0.69-1.68). For bladder cancer, the odds ratio for both men and women was 1.22 (95% CI 0.92-1.62) for 3,000 net rev/liter exposure. However, a higher odds ratio of 2.59 (95% CI 1.13-5.94) for 3,000 net rev/liter exposure was observed for male nonsmokers.
A recent study has revealed that germline mutations of the down-regulated in adenoma (DRA) gene are a likely cause of a recessive intestinal absorption defect, congenital chloride diarrhea. This finding was in accordance with previous works showing that DRA encodes a sodium independent transporter for sulfate and oxalate. Although DRA was originally reported as a candidate tumor suppressor, these studies have questioned the relevance of DRA in cancer. To evaluate whether further studies on the role of DRA in tumorigenesis are still of interest, we examined whether individuals carrying germline DRA mutations have an excess of intestinal cancer. Cancer status of 229 members of 36 Finnish congenital chloride diarrhea families (44 homozygous patients, 70 heterozygous parents, and 115 grandparents at 50% risk of being a DRA mutation carrier) was checked at the Finnish Cancer Registry and the risk of intestinal cancer was found slightly elevated (standardized incidence ratio 3.4, 95% confidence interval 1.4-7.0, P < 0.05). While this result does not unambiguously demonstrate an increased intestinal cancer risk in DRA mutation carriers, it should promote further studies to determine the possible role of DRA in cancer.
Previous job-exposure matrices (JEM) have usually cross-tabulated classified exposure information by chemical agent and occupational class. A new Finnish job-exposure matrix (FINJEM) was constructed for exposure assessment in large register-based studies. Unlike most other JEMs, FINJEM was designed to contain definitions, inferences, exposure data, and references. This documentation enables FINJEM to be applied also as a general exposure information system for hazard control, risk quantification and hazard surveillance. The system includes, e.g., workforce data, and it provides information on the numbers of exposed workers in Finland by agent, occupation, and level of exposure. The exposures of FINJEM cover major physical, chemical, microbiological, ergonomic, and psychosocial factors. The assessment period is 1945-1997, divided into several subperiods. Exposure is described by the prevalence of exposure and the level of exposure among the exposed, both estimated mainly on continuous scales. The user may also define the final criteria of exposure, and thereby influence the magnitude of misclassification.
OBJECTIVES: To assess whether occupational exposure to aromatic hydrocarbons increases carcinogenic risk. METHODS: We followed cancer incidence among 3,922 male and 1,379 female workers monitored for exposure to styrene, toluene, or xylene. The follow-up after the first personal measurement comprised 66,500 person-years at risk over the period 1973-1992. We computed the indirectly standardized incidence ratios (SIR) with 95% confidence interval (CI) with regard to age-, gender-, and period-specific incidence rates of cancer in the Finnish general population. RESULTS: The overall rate of cancer incidence for the total cohort was fairly similar to that of the general population. The risk for nervous system tumors was increased at 10 years after the first personal measurement (SIR 2.80, CI 1.03-6.08). For styrene there was an excess risk for rectal cancer (SIR 3.11, CI 1.14-6.77), and risks for pancreatic and nervous system tumors were increased nonsignificantly. For toluene and xylene, no clear increase in cancer risk was found. CONCLUSIONS: The data are not supportive of an overall increase in the cancer risk for these solvents, even though we cannot rule out site-specific associations with the rectum, pancreas, and nervous system. There is supporting evidence in the epidemiology literature for pancreatic cancer risk and heavy exposure to styrene. More studies are warranted on solvents, with detailed information on lifetime exposures and habits being collected whenever possible.
OBJECTIVES: To assess cancer risk among nickel-exposed workers. METHODS: We updated cancer incidence among 1388 workers employed for at least 3 months at a copper/nickel smelter and nickel refinery in Harjavalta, Finland. There were 1155 workers exposed to nickel during the period 1960-1985 in the smelter (566 workers), repair shop (239 workers), or refinery (418 workers). Cancer incidence was followed through the files of the Finnish Cancer Registry up to 31 December 1995. For overall cancer and for a priori selected specific cancer types the ratio of observed to expected numbers of cases was computed as a standardized incidence ratio (SIR), controlled for age, gender, and calendar period and using the region-specific rates as a reference. RESULTS: The overall cancer incidence among both nickel-exposed and unexposed subcohorts was at the expected level. A small increase in lung cancer incidence, which reached statistical significance among workers with a latency exceeding 20 years, was observed among the smelter workers exposed to insoluble nickel compounds. Among workers in the refinery, who were exposed primarily to nickel sulfate at levels below 0.5 mg/m3 as well as to low concentrations of other nickel compounds, there was an increased risk for nasal cancer (SIR 41.1, 95% CI 4.97-148), positively associated with latency and duration of employment, and an excess risk for stomach (SIR 4.98, 95% CI 1.62-11.6) and lung (SIR 2.61, 95% CI 0.96-5.67) cancers. CONCLUSIONS: Since elevated nasal and lung cancer risks were confined to the refinery, where the primary exposure was to nickel sulfate, it is likely that nickel sulfate is mainly responsible for the elevated respiratory cancer risk. We cannot rule out whether the excess stomach cancer risk is a chance finding, or related to the working environment.
OBJECTIVE: To estimate the subsequent incidence of cancers of endometrium, ovary, vulva, and vagina among women with positive cytology at screening for cervical cancer followed by negative histology. METHODS: This was a longitudinal cohort study involving women attending the organized mass screening in Finland from 1971-1990 with class II, III, IV, or V cytology followed by negative histologic confirmation, and a sample of 42,844 women attending the organized mass screening in Finland in 1971-1976 with cytologic class I smears without any gynecologic symptoms or infections. Follow-up on the women to the end of 1994 for subsequent cancers was maintained by linkage to the national cancer registry. Standardized incidence ratios with 95% confidence intervals (CI), with rates for all of Finland as reference, were estimated. RESULTS: The standardized incidence ratios after negative class I smears of all the cancers studied were between 0.9 and 1.0. Ovarian cancer was not associated with positive cervical cytology. After positive class III-V cytology, the standardized incidence ratio of endometrial carcinoma was 1.6 (CI 1.0, 2.2) and that of vulvar carcinoma was 5.8 (CI 2.3, 12). The standardized incidence ratios of vaginal cancer after class II and III-V cytological smear were 2.7 (CI 1.7, 4.1) and 16.4 (CI 7.1, 32), respectively. The relative risks of all the cancers studied were greatest during the first year of follow-up and persisted for more than 5 years for vulvar and vaginal cancers. CONCLUSION: Although the Papanicolaou smear is poor in detecting cancers other than cervical, in clinical practice, the possibility of other gynecologic cancer has to be considered in surveillance after positive cervical cytology is followed by negative histology.
The EUROCLUS project included information on residence at diagnosis for 13351 cases of childhood leukaemia diagnosed in the period 1980-89 in defined geographical regions in 17 countries. A formal algorithm permits identification of small census areas as containing case excesses. The present analysis examines spatial-temporal patterns of the cases (n = 970) within these clustered areas. The objectives were, first, to compare these results with those from an analysis conducted for UK data for the period 1966-83, and, second, to extend them to consider infant leukaemias. A modification of the Knox test investigates, within the small areas, temporal overlap between cases in a subgroup of interest at a putative critical time and all other cases at any time between birth and diagnosis. Critical times were specified in advance as follows: for cases of acute lymphoblastic leukaemia aged 2-4 years, the 18-month period preceding diagnosis; for cases of total leukaemia aged 5-14 years, 1 year before to 1 year after birth; and for infant cases (diagnosed < 1 year), 1 year before to 6 months after birth. Each of the analyses found evidence of excess space-time overlap compared with that expected; these were 10% (P = 0.005), 15% (P= 0.0002) and 26% (P= 0.03) respectively. The results are interpreted in terms of an infectious origin of childhood leukaemia.