Statistical modelling of breast cancer incidence and mortality rates in Scotland

Mortality of breast cancer in Taiwan, 1971-2010: temporal changes and an age-period-cohort analysis

The current paper describes the age, period and cohort effects on breast cancer mortality in Taiwan. Female breast cancer mortality data were collected from the Taiwan death registries for 1971-2010. The annual percentage changes, age- standardised mortality rates (ASMR) and age-period-cohort model were calculated. The mortality rates increased with advancing age groups when fixing the period. The percentage change in the breast cancer mortality rate increased from 54.79% at aged 20-44 years, to 149.78% in those aged 45-64 years (between 1971-75 and 2006-10). The mortality rates in the 45-64 age group increased steadily from 1971 to 1975 and 2006-10. The 1951 birth cohorts (actual birth cohort; 1947-55) showed peak mortalities in both the 50-54 and 45-49 age groups. We found that the 1951 birth cohorts had the greatest mortality risk from breast cancer. This might be attributed to the DDT that was used in large amounts to prevent deaths from malaria in Taiwan. However, future researches require DDT data to evaluate the association between breast cancer and DDT use.

Trends in invasive breast cancer incidence among French women not exposed to organized mammography screening: an age-period-cohort analysis

BACKGROUND

The long tenure of the Doubs cancer registry (France) and the late implementation of a mass screening program provide a unique opportunity to assess the relative contributions of age, period and cohort effects to the increase in female invasive breast cancer incidence, while avoiding the influence of an organized screening program.

METHODS

Population and incidence data were provided for the Doubs region during the 1978-2003 period. Breast cancer counts and person-years were tabulated into 1-year classes by age and time period. Age-period-cohort models with parametric smooth functions were fitted to the data, assuming a Poisson distribution for the number of observed cases.

RESULTS

A total of 5688 incident cases of invasive breast cancer in women were diagnosed in women aged 30-84 years in the Doubs region between 1978 and 2003. The annual percentage increase in incidence is 2.09%. Age effects rise dramatically until age 50, and at a slower pace afterwards. Large cohort curvature effects (p<10(-6)), show departure from linear trends, with a significant peak for women born around 1940. Period curvature effects are lower in magnitude (p=0.01).

CONCLUSION

Both cohort and period effects are involved in the marked increase in breast cancer incidence over a 25-year period in the Doubs region. Although the future trend for breast cancer incidence is difficult to predict, the introduction of an organized screening program, and the sharp decline in hormone replacement therapy use will likely contribute to period effects in future analyses.

Population-based mammography screening and breast cancer incidence in New South Wales, Australia

OBJECTIVE

To analyse breast cancer incidence trends in New South Wales (NSW), Australia, in relation to population-based mammography screening targeting women aged 50 to 69 years.

METHODS

Trends in age-specific incidence of invasive breast cancers in NSW women aged > or = 40 years were examined in relation to mammography screening rates and screening cancer detection rates.

RESULTS

Incidence of invasive breast cancer in NSW women increased in all age-groups over 1972 to 2002. The incidence trend for women aged 50 to 69 years showed that the steepest rise was associated with increased participation in population-based mammography screening, which was implemented from 1988 and achieved state-wide coverage in 1995. The elevated incidence of invasive cancer significantly exceeded pre-screening levels, and persisted after rates of initial screens declined. This elevated incidence was sustained by the contribution of cancers diagnosed through subsequent screening, and resulted from increased cancer detection rates in subsequent screens.

CONCLUSIONS

The recent increase in invasive breast cancer incidence in NSW is associated with mammography screening, and occurred mostly in the target age-group women. Persistence of higher incidence after 1994 was not explicable by inflation of cancer incidence due to detection of prevalent screen cases, but was associated with a trend of increased cancer detection rates in subsequent screening rounds, probably consequent to quality improvements in mammography screening diagnosis.

Significant difference in the trends of female breast cancer incidence between Taiwanese and Caucasian Americans: implications from age-period-cohort analysis

Female invasive breast cancer (FIBC) in Taiwan is characterized by a striking recent increase of incidence and a relatively young median age (45-49 years) at diagnosis. The Westernization of lifestyle that is increasingly affecting younger generations of Taiwanese may have an important impact on this change. We compared epidemiologic data on FIBC in Taiwanese obtained from the Taiwan Cancer Registry with data for Caucasian Americans obtained from the database of the Surveillance, Epidemiology, and End Results Program for the period from 1980 to 1999. Age-specific incidence rates of FIBC were plotted by calendar year at diagnosis and by birth cohort for both populations. The individual effects of time period and birth cohort on the incidence trends of FIBC in both populations were evaluated using the age-period-cohort analysis. The incidence rate of FIBC was continuously increased in Taiwanese throughout the past 2 decades, whereas the increase of incidence was slowing down in Caucasian Americans. The incidence rates in Taiwanese women born after the 1960s were approaching that of Caucasian Americans. The age-period-cohort analysis showed a much stronger birth cohort effect on the incidence trend of FIBC in Taiwanese than in Caucasian Americans. This strong birth cohort effect corresponded to the Westernization of lifestyle in Taiwan since 1960. These findings indicate that a continued shift in the incidence and age distribution pattern of FIBC in Taiwanese toward that of Caucasian Americans should be anticipated.

Secular trends in cancer mortality, California 1970-1998

BACKGROUND

Monitoring mortality is a meaningful way to evaluate the effectiveness of cancer control activities. Results of trend analysis for cancer related deaths by race/ethnicity in California from 1970 to 1998 are reported here.

METHODS

Age-adjusted cancer mortality rates in California were used in the analysis of secular trends. Mortality patterns for selected cancers in all races combined are compared with similar patterns in the US for 1973-1998.

RESULTS

The overall cancer mortality rates in California began to decline in 1987 in both men and women. Although mortality trends by site, sex, and race/ethnicity showed significant variations, the overall pattern in California is heavily influenced by trends for the non-Hispanic white (NHW) population and is very similar to the patterns in the US with minor differences in the magnitude and trend.

CONCLUSIONS

This is the first time that secular trends in cancer mortality for California are presented by race and ethnicity. Despite notable racial differences, the overall trend follows a declining pattern. Detailed explanation of the reasons behind the observed patterns is not included in this report. Some of the differences between California and the US, however, can be explained by differences in the racial and ethnic composition of the two populations. Approximately 45% of the California population has Hispanic (HSP) or Asian origins among whom cancer mortality rates are substantially lower. Another factor is the difference in the intensity and coverage of cancer related activities such as tobacco control. Prevalence of smoking in California is much lower than the rest of the US.

Age period cohort analysis of time trends in regional mortality rates in England, Wales and Scotland

Previous studies have demonstrated regional variation in mortality rates, this reducing for younger but not older individuals. However, it has not been clear from such studies whether or not the overall findings can or cannot be attributed to particular regions that may have abnormal patterns of change over time. We analyse mortality rates by region using data from the census years from 1931 until 1991 for adults. Age period cohort models, based on the local 'curvatures', are used to describe the changes in the rates. We also use estimable contrasts to compare the later periods with the earlier periods and to compare pre- and post-war cohorts. There is strong evidence that the changes in the mortality rates are associated with non-linear period and cohort effects. There is no evidence that these curvatures vary over regions. There is evidence that the curvatures are not the same among men and women. Among women there is evidence that there is a change in trend in the periods from 1961 to 1991 compared with the trend in the earlier periods from 1931 to 1951, such that the reduction in the mortality rates with time are slowing down for women. Among men who had higher mortality rates, there is not so much evidence of a slowing down of the reduction. Post-war cohorts of women from 1941 onwards are enjoying a reduction in mortality compared with the cohorts from 1901 to 31, while among men there is no evidence of a change in mortality trends among younger cohorts. Changes in the mortality rates over regions have come about from different long-term temporal trends in the regions rather than abrupt changes taking place at different times in different regions. The general convergence of mortality rates over regions over time with a consequent reduction in regional variance is masked by two regions, Scotland and East Anglia. These regions appear to differ from the regions as a whole in the relationship of mortality to age at a given period and in the reduction of mortality over time (drift), Scotland having a higher mortality, especially at younger ages, and lower downward trend, and East Anglia vice versa.

Breast cancer incidence rates in Slovenia 1971-1993

BACKGROUND

Analyses of time trends in breast cancer incidence and mortality have generally revealed cohort-based changes in the rates. These have been linked to cohort-based changes in lifestyle factors. The effect of the changes in the reproductive risk factors on the changes in the rates, and the relative importance of the reproductive characteristics in Slovenia, a country which has not had much breast cancer screening, are investigated.

METHODS

Data on breast cancer incidence for 1971-1993 were obtained from the Cancer Registry of Slovenia (Registry). The Registry covers the whole population of the Republic of Slovenia (1.99 million on 30 June 1993). The statistical analysis uses parametric age-period-cohort models.

RESULTS

Breast cancer incidence has increased by 70% in Slovenia from 1971 to 1993, These changes are dominated by cohort effects and the cohorts born in 1907-1922 have the greatest increase in incidence. Period effects on changes in incidence were modest. The percentage of nulliparous women in the cohort and the average family size in the cohort explained 38% of the variation in the cohort effects.

CONCLUSIONS

The percentage of nulliparous women in the cohort is the most important reproductive variable associated with the trends in the rates, with breast cancer risk predicted to be higher in cohorts with a larger percentage of nulliparous women. As the cohorts born 1932-1946 have a more favourable reproductive pattern as regards breast cancer risk, compared to the 1907-1922 cohorts, age-specific incidence rates in Slovenia would be predicted to decline in the future in the absence of changes in the other risk factors.