To examine the role of gender, age at immigration and length of stay on incidence trends of common cancers, we studied risk of colorectal, lung, breast and prostate cancers in immigrants to Sweden from 1958 to 2008. The nationwide Swedish Family-Cancer Database was used to calculate standardized incidence ratios for common cancers among immigrants compared to Swedes. Immigrants were classified into "high-risk" countries when their risk was increased, into "low-risk" when their risk was decreased and into "other" when their risk was nonsignificant. Among those who immigrated at younger age (
This review aimed at covering cancer risk trends by site and histology in first-generation and second-generation immigrants in Sweden compared with natives. In addition, we reviewed data on cancer survival in immigrants to explore factors explaining cancer survival in the entire population. The Swedish Family-Cancer Database was used to calculate standardized incidence ratios and hazard ratios (HRs) of death from cancer in 77,360 and 993,824 cases among first-generation, and 4356 and 263,485 cases among second-generation immigrants and Swedes, respectively. Ordinal logistic regression analyses were used to calculate odds ratio. To obtain the maximum number of cases, we classified the immigrants according to geographical setting, population, and/or cancer risk. Compared with native Swedes, the highest risk of cancer was observed for nasopharyngeal carcinoma in Southeast Asian men (standardized incidence ratio=35.6) and women (24.6), for hypopharyngeal carcinoma in Indian men (5.4), for squamous-cell carcinoma of the esophagus in Iranian women (3.8), for cardia of the stomach in East Asian women (4.2), for signet-ring cell carcinoma of the stomach in Southeast Asian women (6.7), for the liver in East Asian men (6.8), for the gall bladder in Indian women (3.8), for the pancreas in North African men (2.2), for large cell carcinoma of the lung in former Yugoslavian men (4.2), for pleural mesothelioma in Turkish women (23.8), for the cervix in Danes (1.6), for seminoma in Chileans (2.1), for transitional-cell carcinoma of the bladder in Asian Arab men (2.3), for meningioma in former Yugoslavians (1.3), and for papillary carcinoma of the thyroid in East and Southeast Asian men (3.6). No immigrant groups had an increased risk of breast, uterus, ovary, and prostate cancers or nervous system tumors. The HRs for all breast cancers were between 1.0 in low-risk Europeans and 1.2 in lowest-risk non-Europeans. Low-risk non-Europeans had an HR of 2.9 for lobular carcinoma. Low-risk non-Europeans were diagnosed in a higher T-class (odds ratio=1.9) than Swedes. The HRs for prostate cancer were 0.6 in Turks, Middle Easterners, Asians, and Chileans. In conclusion, environmental and behavioral factors, early-childhood exposures, and infections may play a major role in the risk of esophageal, stomach, liver, nasopharyngeal and hypopharyngeal cancers, malignant pleural mesothelioma, breast, gynecological, testicular, urinary bladder, and thyroid cancers. Pancreatic cancer and nervous system tumors may have a major genetic component in the etiology. The ethnic differences in the risk of breast cancer by histology had no major influence on survival. Middle Easterners, Asians, and Chileans, with the lowest risk of prostate cancer, also had the most favorable survival, suggesting a biological mechanism for this finding.
The observed increased risks of noncardia stomach cancer among foreign-born second-generation immigrants compared to the Swedes suggest that these immigrants were infected by Helicobacter pylori before immigration.
The clinical tumor-node-metastasis (T, N and M) classes of breast cancers provide important prognostic information. However, the possible association of TNM classes with reproductive factors has remained largely unexplored. Because every woman has a reproductive history, implications to outcome prediction are potentially significant.
During the study period from 2002 through 2008, 5,614 pre- and 27,310 postmenopausal patients were identified in the Swedish Family-Cancer Database. Ordinal logistic regression analysis was used to estimate odds ratios (ORs) for TNM classes of breast cancers by histology. The reproductive variables were parity, age at first and last childbirth and time interval between first and last childbirth.
Among postmenopausal patients, the ORs for high-T class (T2-T4) (tumor size =2 cm) and metastasis were decreased by parity. A late age at first and last childbirth associated with high-T class and the effects were higher for lobular (OR for late age at first childbirth ?=?2.85) than ductal carcinoma. Overall, long time interval between first and last childbirth was related to high-T class and metastasis. However, a short time interval between first and last childbirth in patients with late age at first or last childbirth increased the risk of metastasis. Late age at last childbirth was associated with increased occurrence of lobular carcinoma in situ. Among premenopausal ductal carcinoma patients, nulliparity and early age at first childbirth were associated with high-T class.
Increasing parity was protective against high-T class and metastasis; late ages at first and last childbirth were risk factors for high-T class in postmenopausal breast cancers. The current decline in parity and delayed age at first childbirth in many countries may negatively influence prognosis of breast cancer.
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aDivision of Molecular Genetic Epidemiology, German Cancer Research Center (DKFZ), Heidelberg, Germany bCancer Research Center of Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran cCenters for Primary Care Research, Lund University, Malmö, Sweden dStanford Prevention Research Center, Stanford University School of Medicine, California, USA.
Esophageal squamous cell carcinoma is linked to alcohol drinking, whereas esophageal adenocarcinoma risk is increased by overweight and obesity. Both histologies are directly related to tobacco smoking. We wanted to define the risk of esophageal cancer by histology and length of stay among immigrants in Sweden. The nationwide Swedish Family Cancer database (2010 version: data on cancers originate from the nationwide Swedish Cancer Registry) was used to calculate standardized incidence ratios (SIRs) for esophageal cancer among immigrants compared with the native Swedes. SIRs for lung cancer were also calculated as a proxy for smoking prevalence. The patient series covered 5930 male and 1998 female Swedes, and 410 and 198 immigrants. The risk of esophageal cancer was increased in female Finns (SIR=1.66), Britons (3.73), and Southeast Africans (5.26), whereas male Baltic (0.44), former Yugoslavian (0.47), other Europeans (0.58), and other Asians (0.52) showed a decreased risk. The risk of squamous cell carcinoma was increased among Finns (men=1.32, women=1.90) and Iranian women (3.80), whereas Danish men (1.66) had an increased risk of adenocarcinoma. No trend was observed for the risks in immigrants according to the length of stay. We found no covariation between the birth region-specific SIRs for squamous cell carcinoma and lung cancer. Early childhood exposures or preservation of original habits might be the main environmental exposures influencing squamous cell carcinoma risks in some immigrants. The increased risk of adenocarcinoma among Danish men may confirm the role of obesity in adenocarcinoma risk.
There are large geographic differences in breast cancer risk but whether survival differs between low- and high-risk groups is less well-established. As the survival of cancer depends on the level of healthcare and awareness of disease risks, subtle differences in cancer biology cannot be revealed in international comparisons. Instead, comparison of diverse immigrant groups in a country of uniformly accessible healthcare system should enable conclusions to be made about ethnic determinants of cancer risk and survival.
The Swedish Family-Cancer Database was used to calculate standardized incidence (SIRs) and hazard ratios (HRs) of death from female breast cancer in 12 505 and 137 547 patients diagnosed with breast cancer among immigrants and Swedes, respectively. The ratios were adjusted for age, period, region, parity, and age at first childbirth. Ordinal logistic regression analysis was used to estimate odds ratios (ORs) for the clinical TNM classes. The analyses were stratified by menopausal status and histology. Results. Turks, Southeast Asians, and Chileans had the lowest breast cancer risk (SIR = 0.44; 95% CI 0.37-0.51) and Iraqis the highest risk (1.19; 1.05-1.35), mainly due to premenopausal cancer (1.51; 1.27-1.78). The HRs for all breast cancers were between 0.98 (0.81-1.18) (low-risk Europeans) and 1.24 (0.94-1.63) (lowest-risk non-Europeans), but were not significant. No differences in survival of ductal carcinoma between immigrants and Swedes were found, while low-risk non-Europeans had a HR of 2.88 (1.37-6.08) for lobular carcinoma. Low-risk non-Europeans were diagnosed in a higher T-class (OR = 1.87; 1.21-2.87) than Swedes.
We did not find any evidence that ethnic differences in breast cancer risk substantially affect the survival. The observed poor survival of some low-risk immigrants in lobular carcinoma may be related to treatment. The tendency of low-risk immigrants to present with higher T-class compared to Swedes may depend on their lower participation in the mammography screening program.
The changes of cancer incidence upon immigration have been used as an estimator of environmental influence on cancer risk. The previous immigrant studies have indicated that the origins of testicular cancer are at an early age in life, probably in the intrauterine period. We wanted to reexamine the critical periods on histology-specific testicular cancer in sons of immigrants to Sweden. We used the nationwide Swedish Family-Cancer Database to calculate standardized incidence ratios (SIRs) for testicular cancer in sons of parents immigrating to Sweden from low- and high-risk countries compared with the native Swedes. Among the large immigrant groups, the SIRs for sons of two Finnish and Asian parents were decreased if the sons were born outside Sweden. The sons of a Danish immigrant couple showed an increased risk of testicular cancer. The changes in SIR were most systematic for seminoma. The present patterns of testicular cancer risk among sons of immigrants point to the early environmental risk factors, which influence the risk probably after the intrauterine period. These factors appear to influence seminoma risk in a more enduring way than they influence non-seminoma.