Geographic distribution of cervical cancer-associated human leucocyte antigens and cervical cancer incidence in Finland

Cervical cancer (CxCa) is a long-term sequelae caused by persistent human papillomavirus (HPV) infection. Genetic susceptibility to the persistent infection and CxCa is associated with certain human leucocyte antigen (HLA) types. The same susceptibility genes may also determine whether a woman will be protected against the persistent infection and against CxCa by HPV vaccination or not. A systematic review of literature identified following HLAs to be associated with CxCa: A11 (odds ratio [OR] = 1.4, 95% confidence interval [CI] 1.1–2.0); B7 (1.5, 1.1–2.0); B15 (0.6, 0.4–0.8); DR2 (1.2, 1.1–1.4) and DR6 (0.6, 0.5–0.8). In the Caucasian population, HLA-B7 and DR6, and DR2 and B15 antigens showed at least borderline associations. In view of a bone marrow donor registry at the Finnish Red Cross and the Finnish Cancer Registry, we created geographic distribution maps of index HLA frequencies and CxCa incidence in the fertile-aged Finnish population. Increased incidence of CxCa was found in a region of western coastal Finland, where frequency of two CxCa susceptibility genes (HLA-DR2 and B7) was increased, and frequency of one CxCa resistance gene (HLA-B15) was decreased. Whether or not HLA type determines also regional susceptibility to persistent HPV infection, and the success of HPV vaccination in preventing both the persistent infection and CxCa warrants further investigation.

Chernobyl fallout and cancer incidence in Finland

Twenty-five years have passed since the Chernobyl accident, but its health consequences remain to be well established. Finland was one of the most heavily affected countries by the radioactive fallout outside the former Soviet Union. We analyzed the relation of the estimated external radiation exposure from the fallout to cancer incidence in Finland in 1988-2007. The study cohort comprised all ∼ 3.8 million Finns who had lived in the same dwelling for 12 months following the accident (May 1986-April 1987). Radiation exposure was estimated using data from an extensive mobile dose rate survey. Cancer incidence data were obtained for the cohort divided into four exposure categories (the lowest with the first-year committed dose <0.1 mSv and the highest ≥ 0.5 mSv) allowing for a latency of 5 years for leukemia and thyroid cancer, and 10 years for other cancers. Of the eight predefined cancer sites regarded as radiation-related from earlier studies, only colon cancer among women showed an association with exposure from fallout [excess rate ratio per increment in exposure category 0.06, 95% confidence interval (CI) 0.02-0.11]. No such effect was observed for men, or other cancer sites. Our analysis of a large cohort over two decades did not reveal an increase in cancer incidence following the Chernobyl accident, with the possible exception of colon cancer among women. The largely null findings are consistent with extrapolation from previous studies suggesting that the effect is likely to remain too small to be empirically detectable and of little public health impact.

Fallout from the Chernobyl accident and overall cancer incidence in Finland

AIM

We studied whether incidence of all cancer sites combined was associated with the radiation exposure due to fallout from the Chernobyl accident in Finland. An emphasis was on the first decade after the accident to assess the suggested "promotion effect".

METHODS

The segment of Finnish population with a stable residence in the first post-Chernobyl year (2 million people) was studied. The analyses were based on a 250m × 250m grid squares covering all of Finland and all cancer cases except cancers of the breast, prostate and lung. Cancer incidence in four exposure areas (based on first-year dose due to external exposure <0.1 mSv, 0.1-1.3, 0.3-0.5, or ≥ 0.5 mSv) was compared before the Chernobyl accident (1981-1985) and after it (1988-2007) taking into account cancer incidence trends for a longer period prior to the accident (since 1966).

RESULTS

There were no systematic differences in the cancer incidence in relation to radiation exposure in any calendar period, or any subgroup by sex or age at accident.

CONCLUSION

The current large and comprehensive cohort analysis of the relatively low levels of the Chernobyl fallout in Finland did not observe a cancer promotion effect.

Nationwide registry-based analysis of cancer clustering detects strong familial occurrence of Kaposi sarcoma

Many cancer predisposition syndromes are rare or have incomplete penetrance, and traditional epidemiological tools are not well suited for their detection. Here we have used an approach that employs the entire population based data in the Finnish Cancer Registry (FCR) for analyzing familial aggregation of all types of cancer, in order to find evidence for previously unrecognized cancer susceptibility conditions. We performed a systematic clustering of 878,593 patients in FCR based on family name at birth, municipality of birth, and tumor type, diagnosed between years 1952 and 2011. We also estimated the familial occurrence of the tumor types using cluster score that reflects the proportion of patients belonging to the most significant clusters compared to all patients in Finland. The clustering effort identified 25,910 birth name-municipality based clusters representing 183 different tumor types characterized by topography and morphology. We produced information about familial occurrence of hundreds of tumor types, and many of the tumor types with high cluster score represented known cancer syndromes. Unexpectedly, Kaposi sarcoma (KS) also produced a very high score (cluster score 1.91, p-value <0.0001). We verified from population records that many of the KS patients forming the clusters were indeed close relatives, and identified one family with five affected individuals in two generations and several families with two first degree relatives. Our approach is unique in enabling systematic examination of a national epidemiological database to derive evidence of aberrant familial aggregation of all tumor types, both common and rare. It allowed effortless identification of families displaying features of both known as well as potentially novel cancer predisposition conditions, including striking familial aggregation of KS. Further work with high-throughput methods should elucidate the molecular basis of the potentially novel predisposition conditions found in this study.

Chlamydia trachomatis seroprevalence atlas of Finland 1983-2003

OBJECTIVES

To study Chlamydia trachomatis seroprevalence trends and geographical distribution over time in Finland.

MATERIALS AND METHODS

First pregnancy serum samples were retrieved from the Finnish Maternity Cohort serum bank for the subcohort of 8000 women stratified by calendar years (1983-1989, 1990-1996, 1997-2003) and age at time of sample withdrawal (14-22 and 23-28 years). C trachomatis antibodies were determined using standard major outer membrane protein peptide ELISA. The spatiotemporal variation of C trachomatis seroprevalence rates was visualised by a series of maps.

RESULTS

A decreasing C trachomatis seroprevalence trend from 1983 to 2003 was seen for both women under 23 years of age (20.8% to 10.6%) and 23-28-year-old women (19.1% to 12.5%). Constant clusters were seen around the largest cities and in eastern Finland although seroprevalence rates were generally decreasing throughout the country.

CONCLUSIONS

Only a few population-based serological studies have been undertaken on C trachomatis epidemiology over time. In Finland the seroprevalence of C trachomatis is decreasing all over the country, albeit with small clusters remaining.

Seroprevalence atlas of infections with oncogenic and non-oncogenic human papillomaviruses in Finland in the 1980s and 1990s

Vaccines against high-risk (hr) human papillomaviruses (HPVs) causing cervical cancer may soon be licensed. Thus, nature of HPV epidemics needs to be studied now. Random sampling for studies on HPV epidemiology was done from all 230,998 women belonging to the population-based Finnish Maternity Cohort and having a minimum of 2 pregnancies between 1983 and 1994. First pregnancy serum specimens were retrieved for 7,805 subjects, and were analyzed for antibodies to HPV6/11, 16 and 18 with standard ELISAs. HPV16 seroprevalence almost doubled from the 1980s to the 1990s, and the epidemic spread to new areas in 23-31 year olds, i.e. the bulk of pregnant female population in the southwest part of the country. The HPV16 epidemic in the 14-22 year olds in 1983-1988 (1961-1974 birth cohorts) and in the 23-31 year olds in 1989-1994 (1958-1971 birth cohorts) overlapped with strong clustering of HPV16 and HPV18 infections in the latter (odds ratio 8.0, 95% confidence interval 6.6-9.7). Similar clustering of HPV16 and HPV6/11 infections was not found. The epidemic and the clustering may be due to high transmission probability of the hrHPV types and increase in sexual activity of the index birth cohorts.