The Inuit cancer pattern--the influence of migration

The Inuit cancer pattern is characterized by high frequencies of Epstein-Barr Virus (EBV)-associated carcinomas of the nasopharynx and salivary glands. The reasons are unknown, but genetic and environmental factors are believed to be involved. Using data from the well-defined Inuit population in Greenland we investigated whether migration to Denmark influenced their risk of cancer. Greenland is part of the Danish Kingdom, and population-based registries cover both countries. Using rates for Denmark as reference, sex-specific standardized incidence ratios (SIR) were calculated for Inuit who never lived in Denmark and for those who at least once were registered with a Danish address. During 1973-2003, we observed 3,567 cancers in a cohort of 77,888 persons. Of these, 862 among 26,214 Inuit ever living in Denmark, and 2,705 among 51,674 nonmigrating Inuit. High SIRs for cancers of the nasopharynx [31.7 (CI 22.0-45.5)] and salivary glands [3.1 (CI 1.4-6.9)] observed among Inuit migrating to Denmark were comparable to those observed among Inuit never living in Denmark. Significant higher risk of cancer of the bladder, breast, prostate gland, skin, brain and stomach was observed among Inuit following migration to Denmark. The SIR was not generally influenced by duration of stay. The high risk of carcinoma of the nasopharynx and salivary glands observed in Inuit populations is maintained after migration to a low incidence area. This indicates that genetic factors or environmental factors acting early in life are etiologically important for these cancers.     

Cancer in Circumpolar Inuit

The cancer patterns among Inuit in the Circumpolar area have shown some marked differences from other populations in the world. The current paper summarizes important risk factors in Alaska including the physical environment, diet, alcohol, tobacco; the populations at risk; the health care delivery system; and cancer registration. This information is important for the interpretation of the incidence pattern for the Circumpolar Inuit collectively and for the understanding of differences between the various Inuit populations of the North.     

Cancer in Circumpolar Inuit: Background information for cancer patterns in Canadian Inuit

The cancer pattern among Inuit in the Circumpolar area is remarkably different from those of other populations in the world. The current paper summarizes the most important risk factors in Canadian Inuit residing in the Northwest Territories, northern Quebec (Nunavik) and Labrador, particularly during the time period 1969-1988 covered by the study. Factors considered include: the geographic area and physical environment; population and human environment, including fertility and life expectancy; lifestyle and diet, including tobacco and alcohol use; other lifestyle factors, and health conditions; and health services and cultural accessibility. Development of the cancer registry and population databases supporting the analysis of cancer rates is described. The information in the present paper is needed to interpret cancer incidence patterns and differences among the Circumpolar Inuit of Canada, Alaska and Greenland.     

Breast Cancer in Circumpolar Inuit 1969-1988

Breast cancer was studied over a 20-year period in Inuit populations in the Circumpolar region. A total of 193 breast cancers were observed in women. The incidence increased from 28.2 per 100000 in 1969-1973 to 34.3 per 100 000 in 1984-1988. However, the incidence is low, about half what could be expected based on the rates in Denmark, Canada and Connecticut (USA). The low incidence could be explained by the Inuit diet and other lifestyle factors. These benefits should be preserved, in particular in the young, to maintain a low breast cancer incidence.     

Cancers of Skin, Bone, Connective Tissues, Brain, Eye, Thyroid and Other Specified and Unspecified Sites in Inuit

Low rates of skin'cancer, both melanoma and non-melanoma, were observed in Inuit after 20 years of observation. Tumours of the brain and central nervous system, of the thyroid, bone and connective tissues and other specified sites occurred with rates similar to those in comparison populations in Denmark, Connecticut and Canada. These findings support that neither UV and ionizing radiation from nuclear fall-out, nor pollution of herbicides and pesticides in the Arctic area have yet had any noticeable impact on cancer risk. However, unspecified and secondary neoplasms constititute 7-8% of the total Circumpolar cancer incidence and the pattern of rare cancers must be enterpreted with caution. Increased diagnostic efforts with a higher precision in the future are warranted.     

Cancer in Circumpolar Inuit 1969-1988

The results of an international, collaborative study of cancer in Circumpolar Inuit in Greenland, Canada, Alaska and Russia are summarized. A total of 3 255 incident cancers were diagnosed from 1969 to 1988 among 85 000-110 000 individuals. Indirect standardization (SIR) based on comparison populations in Connecticut (USA), Canada and Denmark showed excess risk of cancer of the lung, nasopharynx, salivary glands, gallbladder and extrahepatic bile ducts in both sexes, of liver and stomach cancer in men, and renal and cervical cancer in women. Low risk was observed for cancer of the bladder, breast, endometrium and prostate, and for non-Hodgkin lymphoma, Hodgkin's disease, leukaemia, multiple myeloma and melanoma. Age-standardized incidence rates (ASRs) of cancer of lung, cervix, nasopharynx and salivary glands among Inuit were among the world's highest as were rates in women of oesophageal and renal cancer. Regional differences in ASRs within the Circumpolar area were observed for cancer of the cervix, lung, colon and rectum, liver, gallbladder and breast. The differences in the Inuit cancer incidence pattern to some extent reflect known variations in lifestyle, diet and other exposures, as well as implementation of cancer control measures. Future research addressing possible individual differences are needed to evaluate environmental and genetic factors in etiology and evaluate intervention studies.     

Cancer of the Digestive System in Circumpolar Inuit

Cancer of the oesophagus, stomach, small intestine, colon, rectum, liver, gallbladder, biliary tract and pancreas was studied in the Inuit populations of Alaska, Canada and Greenland. Indirect standardization to the populations in Canada, Connecticut (USA) and Denmark was used. High risk of oesophageal cancer was observed in both sexes with standardized incidence ratios (SIRs) of up to 7. An increased risk of colon and rectum cancer occurred among Alaskan Inuit compared with the Inuit populations in Canada and Greenland, which had lower rates. Liver and gallbladder cancer rates were high, with SIRs of 1.5 to 4.1, whereas there were no differences in pancreatic cancer in the populations compared. Dietary habits, alcohol and tobacco consumption are believed to play an important role in most of the observed cancer patterns, but for liver cancer hepatitis B virus infection is also believed to have a causal role.     

Cancer pattern among Greenlandic Inuit migrants in Denmark, 1968-1982

For several cancer sites the incidence among Inuit (Eskimos) in Alaska, Canada and Greenland differs markedly from that in non-Inuit in adjacent areas. This is the first study of Inuit migrants. Among 11,571 Inuit Greenlandic people living in Denmark in the period 1968-1982 we found 69 cases of cancer. Significantly increased risks compared to the Danish population were found for cancer of the rectum (RR = 5.5) in males and for nasopharyngeal cancer (RR = 185.2) and cancer of the cervix uteri (RR = 1.9). The significance of these findings in relation to the role of environmental factors in the aetiology of cancer in Inuit is discussed.     

Epidemiology of lung cancer: looking to the future.

In the United States, the 20th century witnessed the emergence of a lung cancer epidemic that peaked and began to decline by the century's end, a decline that continues today. However, lung cancer continues to be an unabating pandemic. In research carried out over the last half of the 20th century, many factors were causally associated with lung cancer and studies were implemented to identify determinants of susceptibility to these factors. Cigarette smoking was identified as the single most predominant cause of the lung cancer epidemic, but other causes were found, including workplace agents (eg, asbestos, arsenic, chromium, nickel, and radon) and other environmental factors (passive smoking, indoor radon, and air pollution). Contemporary epidemiologic research on lung cancer now focuses on a new set of issues, primarily related to susceptibility to the well-identified causal factors, particularly smoking, and on the consequences of changes in tobacco products for risks to smokers. Diet and the possibility of reducing risk through chemoprevention remain a focus of research emphasis through experimental and observational approaches. Questions have also been raised about possible differences in susceptibility to lung cancer by sex and race.Population patterns in smoking prevalence will continue to be the most powerful predictor of the future occurrence of lung cancer. Evaluation of recent US patterns in smoking prevalence indicates that for the next approximately 10 to 15 years, lung cancer rates will decrease, but will then level off starting in approximately 2030. Unless further reductions in the prevalence of cigarette smoking are achieved over the next decade, lung cancer will remain as an all too common, but avoidable, disease.     

Cancers of the Buccal Cavity and Pharynx in Circumpolar Inuit

In an international collaboration, cancers of the buccal cavity and pharynx were combined from cancer registries in the Circumpolar region, including Alaska, Canada and Greenland. Low risk of cancers of the lip (SIR 0.2) was observed among Inuit. Increased risk of cancer of the tongue and oral cancer (SIR 2.5) were observed among Greenlandic Inuit men. Salivary gland cancer and nasopharyngeal cancer occur among Inuit with rates among the highest in the world. Environmental factors (EBV, diet) and a genetically susceptible population are believed to play a role.     

Cancer of the Respiratory System in Circumpolar Inuit

Cancer incidence of the nasal cavities in Inuit men are high (ASR=3.0 1984-1988), and higher than seen in Denmark, Connecticut (USA) and Canada. Lung cancer incidence is among the highest in the world, for both men and women, and larynx cancer among the lowest. The smoking pattern among Inuit, possibly combined with co-factors related to environment and diet, are believed to be the relevant causal factors.     

Cancer of the Female Genital Tract in Circumpolar Inuit

Cervical cancer incidence among Inuit is high. Especially women from Greenland exhibit rates which are among the highest in the world. Compared with women in Denmark, USA and Canada, Inuit women have a 3-4 time higher cervical cancer risk. By contrast, the incidence of uterine corpus cancer is low in the Circumpolar area. Both in Greenlandic and Canadian Inuit women, ovarian cancer rates are similar to those in Danish women and non-Inuit women from Canada respectively. Only 9 cases of placenta cancer were recorded in the Circumpolar area during the 20 years of observation. Compared with available incidence rates for Denmark the incidence in Greenland was significantly higher.     

Malignant Neoplasms of the Lymphatic and Haematopoietic System in Circumpolar Inuit

Malignancies of the lymphatic and haematopoietic system in Circumpolar Inuit were studied as part of an international collaboration combining results from cancer registries for Alaska, Canada and Greenland. Low risk was observed for all such malignancies, including non-Hodgkin lymphoma, Hodgkin's disease, multiple myeloma and the combined leukaemias. Standardized incidence ratios (SIRs) of non-Hodgkin lymphoma ranged from 0.3 to 0.5 based on comparison populations in Connecticut (USA), Canada and Denmark. SIR of Hodgkins's disease ranged from 0.1 to 0.2. Acute leukaemias accounted for 78% of all microscopically verified leukaemias and chronic leukaemias for 6%. No clear time trends were observed except for increasing rates of the combined leukaemias among women from the first to the second half of the study period. The epidemiology of haematologic and Iympoproliferative malignancies in Inuit is comparable to results from Chinese and Japanese populations in Asia and may reflect protective environmental or genetic factors for these malignancies.     

Cancer in Russian Inuit

Using the framework of the Native Cancer Registry, cancer morbidity among Russian Inuit can be obtained from 1960 onwards. Earlier data are available, but have not been verified. Unfortunately, the absence of accurate demographic data for the Native population of about 16 000 people, including the increase from 1 149 to 1 452 Inuit between 1970 and 1989 prevents comparison and analysis of morbidity and mortality data with the non-Inuit population. Nevertheless, the number of cancers has risen in the Native population of Chukotka during the last decade (1979-1988), with a predominance of oesophagus, lung and stomach cancer among the Inuit. In contrast, no cases were observed of the salivary gland, nasopharyngeal and cervical cancers common in other Inuit populations.     

The epidemiology of oral and pharynx cancer in Brazil

A study was carried out on the occurrence of oral and pharynx cancer among populations living in five Brazilian geographic regions, by using incidence and mortality rates and trends. Information on survival was also analyzed. Complementary information regarding prevalence of the disease risk factors has been supplied in the attempt to establish some etiological connections with the incidence and mortality observed. Two clear patterns for the occurrence of oral and pharyngeal cancer have been detected: a pattern for the north (including the northern, northeastern and midwestern regions, which are the poorest ones) and a pattern for the south (including the southern and southeastern regions). The southern pattern revealed incidence rates higher than 15 per 100,000 among males, and the northern pattern displayed lower rate levels. Similarly, mortality rates in the south were higher than three per 100,000 and the northern pattern was characterized by lower rates. Other cancers linked to tobacco smoking, such as esophagus, larynx, lung and bladder cancer kept the same pattern of incidence and mortality rates related to oral and pharyngeal cancer in males per region. Information on survival of patients with oral and pharyngeal cancer was very restricted in Brazil, thus hindering the survival analysis per region, but the studies conducted allowed to conclude that the majority of diagnoses were conducted in advanced stages of the disease and implied the low 5-year survival rate observed in Brazil. Tongue tumors displayed the worst survival rates. The southern region shares specific risk factors involved in the oral and pharyngeal cancer present in the Argentinean and Uruguayan populations, namely heavy tobacco smoking and alcohol consumption, as well as high intake of charcoal-grilled red meat and mate. In addition to these risks, part of the oral and pharyngeal cancer registered in Brazil might be linked to a few factors present among people with low life standards, including poor oral hygiene and nutrition.     

Epidemiology of testicular cancer: an overview

Testicular cancer is a rare disease, accounting for 1.1% of all malignant neoplasms in Canadian males. Despite the low overall incidence of testicular cancer, it is the most common malignancy among young men. The incidence rate of testicular cancer has been increasing since the middle of the 20th century in many western countries. However, the etiology of testicular cancer is not well understood. A search of the peer-reviewed literature was conducted to identify important articles for review and inclusion in this overview of the epidemiology of testicular cancer. Most of the established risk factors are related to early life events, including cryptorchidism, carcinoma in situ and in utero exposure to estrogens. Occupational, lifestyle, socioeconomic and other risk factors have demonstrated mixed associations with testicular cancer. Although there are few established risk factors for testicular cancer, some appear to be related to hormonal balance at various life stages. Lifestyle and occupational exposures occurring later in life may play a role in promoting the disease, although they are not likely involved in cancer initiation. In addition to summarizing the current epidemiologic evidence on risk factors for testicular cancer, we suggest future research directions that may elucidate the etiology of testicular cancer.     

高原地区肺癌患者放疗后发生放射性肺损伤的危险因素

目的：探讨影响高原肺癌患者发生放射性肺损伤的危险因素。方法：采用回顾性病例对照研究分析我院183例肺癌患者接受放射治疗后发生 RILI 的危险因素。运用单因素χ2检验和多因素 Logistic 回归分析独立影响因素,Kaplan - Meier 分析比较两组患者的生存情况及血液毒性变化。结果：经单因素分析发现民族、常住地、合并慢性肺炎、合并慢性病和V 20有统计学意义（χ2=8.548、40.539、6.941、8.117、41.79,P <0.05）。多因素分析发现民族、常住地、合并慢性肺炎和 V20是独立的危险因素（P <0.05）。放疗开始对患者的血液变化影响较大,尤其是 WBC 等。生存分析显示对照组中位生存期16个月明显高于病例组11个月（P<0.05）。结论：影响患者发生 RILI 因素很多,应该根据患者基本情况适当调整放射治疗方案,以降低 RILI的发病风险。     

Cancer incidence in adults living in the vicinity of nuclear power plants in France,based on data from the French Network of Cancer Registries

Nuclear power plants (NPPs) release toxic emissions into the environment that may affect neighboring populations. This ecologic study was designed to investigate the possibility of an excess incidence of cancer in the vicinity of French NPPs by examining the incidence by municipality of 12 types of cancer in the population aged 15 years and older during the 1995–2011 period. Population exposure to pollution was estimated on the basis of distance from towns of residence to the NPP. Using regression models, we assessed the risk of cancer in a 20‐km zone around NPPs and observed an excess incidence of bladder cancer (Relative Risk (RR), 95% Credibility Interval (95% CI)) in men and women (RR_men = 1.08; 95% CI: 1.00, 1.17 and RR_women = 1.19; 95% CI: 1.02, 1.39). Women living within the 20‐km proximity areas had a significantly reduced risk of thyroid cancer (RR_women = 0.86; 95% CI: 0.77, 0.96). No excess risk of hematologic malignancies in either sex was seen. The higher than expected incidence of bladder cancer may be due to an excess incidence localized around the Flamanville NPP and the nearby La Hague nuclear waste treatment center, which is a source of chemical contaminants, many (including arsenic) of them known risk factors for bladder cancer. Differences in medical practices could explain the reduced risk of thyroid cancer. In this first study of adults living near NPPs in France, cancer incidence is significantly higher than in the references populations for one of the cancer types studied: bladder cancer.     

Risk factors for HPV infection in women from sexually transmitted disease clinics: Comparison between two areas with different cervical cancer incidence

We have compared risk factors for human papillomavirus (HPV) infection in very sexually active women [attenders of clinics for sexually transmitted diseases (STDs)] living in 2 areas with a 4-fold difference in cervical cancer incidence, i.e., Greenland and Denmark. The results were compared with findings of HPV infection in men attending the STD clinics during the same period. Overall, 204 Greenlandic women (GW), 187 Danish women (DW), 103 Greenlandic men and 216 Danish men were included. A similar age distribution was found in the 2 female populations. The GW reported significantly more sexual partners, earlier first intercourse and more STDs, but HPV was less frequently detected in the GW (25%) than in the DW (35%). However, this could be explained by a difference in the age pattern of HPV prevalence seen in the 2 areas. In each geographical area, the age pattern of HPV prevalence in men was very similar to that seen in women. The most important risk factors for HPV detection were the same in both female populations, i.e., age, years since first sexual intercourse and number of partners in the last years. In conclusion, the pattern of risk factors for HPV infection was the same in STD women from a high-risk area and a low-risk area for cervical cancer. Our results also show that the use of an overall HPV prevalence for comparing populations is meaningless, even in populations with similar age distribution. Int. J. Cancer 75:1–8, 1998.© 1998 Wiley-Liss, Inc.     

Epidemiology of in situ and invasive breast cancer in women aged under 45.

The incidence of in situ breast cancer in the USA has increased rapidly in recent years, even among young women. A population-based case-control study of 1616 breast cancer cases aged under 45 in the USA was used to examine risk factors for in situ, local and regional/distant tumours. Almost 60% of in situ tumours were detected by routine mammograms compared with 18% of local tumours and 8% of regional/distant tumours. After adjustment for screening history and established risk factors, family history of breast cancer in a first-degree relative and African-American race were associated with an increased risk of all stages of breast cancer. The associations with nulliparity, a previous breast biopsy and body mass index were significantly stronger for in situ tumours than for local or regional/distant disease. Alcohol consumption was associated with an increasing trend in risk of regional/distant tumours but not of earlier stage tumours, indicating that alcohol may be involved in late-stage events. Analyses by histological type of in situ tumours suggested that both ductal and lobular carcinoma in situ were associated with most established breast cancer risk factors, and the magnitude of association tended to be greater for the ductal form.