Biomedical subjects
Publications and source records attributed to L Barlow.
Breast cancer incidence in Sweden during the period 1984-93 shows no clear trend in women aged below 40 years but a transient increase at ages 50-69 years, probably as a result of mammography screening. Our data give no indication that use of oral contraceptives or replacement hormones have affected nationwide breast cancer incidence rates.
Until the introduction of self-service around 1970, service station workers in the Nordic countries were exposed to gasoline vapors. Based on measurements reported in the literature, the 8-hour time-weighted average benzene exposure was estimated to be in the range of 0.5-1 mg/m3. We studied the cancer incidence in a cohort of 19,000 service station workers from Denmark, Norway, Sweden, and Finland. They were identified from the 1970 censuses and followed through 20 years, where 1,300 incident cancers were observed. National incidence rates were used for comparison. The incidence was not increased for leukemia (observed = 28, standardized incidence ratio (SIR) = 0.9, 95% confidence interval (CI) 0.6-1.3) not for acute myeloid leukemia (observed = 13, SIR = 1.3, 95% CI 0.7-2.1). The incidence was slightly elevated for kidney cancer observed = 57, SIR = 1.3, 95% CI 1.0-1.7) and for pharyngeal, laryngeal, and lung cancer. A 3.5-fold risk of nasal cancer was found (observed = 12, SIR = 3.5, 95% CI 1.8-6.1). This cohort exposed to gasoline vapors with benzene levels estimated to be 0.5-1 mg/m3 showed no excess risk of leukemia or acute myeloid leukemia, a 30% elevated risk of kidney cancer, and a previously unnoticed risk of nasal cancer.
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.
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.
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.
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The theory that cancer may arise under conditions of reduced immune capacity is supported by observations of humans with immune deficiencies such as occur following organ transplants. However, no study on humans has been done in which the reference population was the same as that in which the cancer cases arose and in which there was a sufficiently long period of follow-up. Information on 5,692 Nordic recipients of renal transplants in 1964-1982 was linked with the national cancer registries (1964-1986) and population registries. Person-years at risk were calculated from the date of first transplantation until death or the end of the study period and were multiplied by the appropriate age- and calender-specific incidence rates to obtain the expected numbers of cancers. Standardized incidence ratios (SIR) were calculated after stratification by a number of recorded variables. Altogether, 32,392 person-years were accrued, and 471 cancers occurred, yielding overall SIR of 4.6 (95% CI, 4.0 to 5.2) for males and 4.5 (95% CI, 4.0 to 5.2) for females. Significant overall 2- to 5-fold excess risks in both sexes were seen for cancers of the colon, larynx, lung and bladder, and in men also for cancers of the prostate and testis. Notably high risks, 10-fold to 30-fold above expectation, were associated with cancers of the lip, skin (non-melanoma), kidney and endocrine glands, also with non-Hodgkin's lymphoma, and in women also with cancers of the cervix and vulva-vagina. Among a number of donor and recipient variables studied, including tissue types and compatibility (ABO, HLA, DR), age below 45 years at the time of transplantation was the most important determinant for increased risk at most sites. Kidney transplantation increases the risk of cancer in the short and in the long term, consistent with the theory that an impaired immune system allows carcinogenic factors to act. The tumor risk is small in comparison with the benefits of transplants, but patients should be followed up for signs of cancer.
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The incidence of ovarian cancer and non-Hodgkin's lymphomas (NHL) between 1971 and 1985 or 1987 has been studied on the basis of cancer registry data among women employed in hairdressing or related occupations at 1970 census in Denmark, Sweden, Norway, and Finland. Overall, the standardized incidence ratio (SIR) for ovarian cancer was 1.18 (95% confidence interval, 0.98 to 1.40). The increase was present among hairdressers from Denmark (SIR, 1.23) and Finland (SIR, 1.88); whereas hairdressers from Sweden and Norway had an incidence close to expectation (SIR 0.95 and 0.96, respectively). In three of the four countries, the SIR was higher in 1971 to 1975 than in later years. The SIR for NHL was 1.20 (0.84 to 1.66); an excess was seen in Denmark (SIR, 1.92) and a decrease was found in Sweden (SIR, 0.63). In previous studies, hairdressers have been reported to be at increased risk of ovarian cancer: this study adds some evidence in favor of the presence of an association. This study also offers some support to the hypothesis of an association between exposure to hair dyes and risk of NHL, that was reported among personal users from the United States. This study, however, strongly suggests that occupational cancer risk among female hairdressers depends on temporal and geographical factors.
OBJECTIVE: To obtain further information about the risks of childhood leukaemia after exposure to ionising radiation at low doses and low dose rates before or after birth or to the father's testes shortly before conception. DESIGN: Observational study of trends in incidence of childhood leukaemia in relation to estimated radiation exposures due to fallout from atmospheric nuclear weapons testing during the 1950s and 1960s. SETTING: Nordic countries. SUBJECTS: Children aged under 15 years. MAIN OUTCOME MEASURES: Incidence rates of leukaemia by age at diagnosis, sex, country, and calendar year of diagnosis or year of birth; exposure category; relation between leukaemia and exposure for children aged 0-14 and 0-4 separately. RESULTS: During the high fallout period the average estimated dose equivalent to the fetal red bone marrow was around 140 mu Sv and the average annual testicular dose 140 mu Sv. There was little evidence of increased incidence of leukaemia among children born in these years. Doses to the red bone marrow of a child after birth were higher, and during the high exposure period children would have been subjected to an additional dose equivalent of around 1500 mu Sv, similar to doses received by children in several parts of central and eastern Europe owing to the Chernobyl accident and about 50% greater than the annual dose equivalent to the red bone marrow of a child from natural radiation. leukaemia incidence and red marrow dose was not related overall, but rates of leukaemia in the high exposure period were slightly higher than in the surrounding medium exposure period (relative risk for ages 0-14: 1.07, 95% confidence interval 1.00 to 1.14; for ages 0-4: 1.11, 1.00 to 1.24). CONCLUSIONS: Current predicted risks of childhood leukaemia after exposure to radiation are not greatly underestimated for low dose rate exposures.
Both twins in a pair in which one had suffered breast cancer (115 pairs) were asked about the occurrence of cancer among first- and second-degree relatives. For all cancer sites together, there was agreement about 129 cases; another 48 cancers were mentioned only by the case twin and another 55 only by the co-twin. For breast cancer, there was agreement about 22 events; another 12 cases were provided by the cancer twin and four by the co-twin. The odds ratio for a family history of cancer was 1.14; for breast cancer the corresponding value was 1.48. The results are suggestive of some recall bias in subjective reports on familial cancer.
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