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

Temporal Pattern and Age-Period-Cohort Analysis of Breast Cancer Incidence in Iranian Women (2009-2017)

BACKGROUND

Breast cancer accounted for 28.1% of all female cancers in 2020 in Iran. This study was conducted to evaluate the time trend of breast cancer incidence and to identify the changes of breast cancer incidence in age, period, and birth cohorts in Iran, in the 2009-2017 timeframe.

METHODS

Annual cancer statistics for female breast cancer were obtained from the Iranian National Population-based Cancer Registry (INPCR) database from 2009 to 2017. The age-period-cohort (APC) analysis was used to evaluate the time trend of breast cancer incidence in age, period and birth cohorts between 2009 and 2017. R package (Epi) was used to analyze data. Results were considered statistically significant at P<0.05.

RESULTS

The age effect showed an increased incidence of breast cancer until the age of 45, and after this age the speed of increase was slower until 65 years. There was an increased diagnosis in 2015-2017 (period effect) for many age groups, especially in the 70- and over 80-year-old group.

CONCLUSION

Our findings indicated that breast cancer incidence peaks in the age of 45 in Iranian women, which is a decade earlier compared to the Western world. The period effect in 2015-2017 can be explained by the fact that in 2014, the former Iranian pathology-based cancer registry was upgraded to a population-based cancer registry, which resulted in improved coverage of cancer registry and case finding.

Age-period-cohort analysis with a constant-relative-variation constraint for an apportionment of period and cohort slopes

Age-period-cohort analysis of incidence and/or mortality data has received much attention in the literature. To circumvent the non-identifiability problem inherent in the age-period-cohort model, additional constraints are necessary on the parameters estimates. We propose setting the constraint to reflect the different nature of the three temporal variables: age, period, and birth cohort. There are two assumptions in our method. Recognizing age effects to be deterministic (first assumption), we do not explicitly incorporate the age parameters into constraint. For the stochastic period and cohort effects, we set a constant-relative-variation constraint on their trends (second assumption). The constant-relative-variation constraint dictates that between two stochastic effects, one with a larger curvature gets a larger (absolute) slope, and one with zero curvature gets no slope. We conducted Monte-Carlo simulations to examine the statistical properties of the proposed method and analyzed the data of prostate cancer incidence for whites from 1973-2012 to illustrate the methodology. A driver for the period and/or cohort effect may be lacking in some populations. In that case, the CRV method automatically produces an unbiased age effect and no period and/or cohort effect, thereby addressing the situation properly. However, the method proposed in this paper is not a general purpose model and will produce biased results in many other real-life data scenarios. It is only useful in situations when the age effects are deterministic and dominant, and the period and cohort effects are stochastic and minor.

Change in mammographic density across birth cohorts of Dutch breast cancer screening participants

High mammographic density is a well‐known risk factor for breast cancer. This study aimed to search for a possible birth cohort effect on mammographic density, which might contribute to explain the increasing breast cancer incidence. We separately analyzed left and right breast density of Dutch women from a 13‐year period (2003–2016) in the breast cancer screening programme. First, we analyzed age‐specific changes in average percent dense volume (PDV) across birth cohorts. A linear regression analysis (PDV vs. year of birth) indicated a small but statistically significant increase in women of: 1) age 50 and born from 1952 to 1966 (left, slope = 0.04, p = 0.003; right, slope = 0.09, p < 0.0001); 2) age 55 and born from 1948 to 1961 (right, slope = 0.04, p = 0.01); and 3) age 70 and born from 1933 to 1946 (right, slope = 0.05, p = 0.002). A decrease of total breast volume seemed to explain the increase in PDV. Second, we compared proportion of women with dense breast in women born in 1946–1953 and 1959–1966, and observed a statistical significant increase of proportion of highly dense breast in later born women, in the 51 to 55 age‐groups for the left breast (around a 20% increase in each age‐group), and in the 50 to 56 age‐groups for the right breast (increase ranging from 27% to 48%). The study indicated a slight increase in mammography density across birth cohorts, most pronounced for women in their early 50s, and more marked for the right than for the left breast.

What's new?

Women with dense breast tissue are at increased risk of breast cancer. Here, changes in mammographic density were investigated across birth cohorts in women enrolled in a breast cancer screening program in the Netherlands. The findings reveal an increase in the average fraction of dense tissue in the breast across cohorts. In particular, greater breast density was observed in a higher proportion of women in later‐born than earlier‐born birth cohorts. The increase was most significant among women in their early 50s and may be linked to a reported shift toward older age at menopause among women in Europe.

Use of age-period-cohort analysis in cancer epidemiology research

PURPOSE OF REVIEW

Age-period-cohort (APC) models simultaneously estimate the effects of age - biological process of aging; time period - secular trends that occur in all ages simultaneously; and birth cohort - variation among those born around the same year or from one generation to the next. APC models inform understanding of cancer etiology, natural history, and disparities. We reviewed findings from recent studies (published 2008-2018) examining age, period, and cohort effects and summarized trends in age-standardized rates and age-specific rates by birth cohort. We also described prevalence of cancer risk factors by time period and birth cohort, including obesity, current smoking, human papilloma virus (HPV), and hepatitis C virus (HCV).

RECENT FINDINGS

Studies (n=29) used a variety of descriptive analyses and statistical models to document age, period, and cohort trends in cancer-related outcomes. Cohort effects predominated, particularly in breast, bladder, and colorectal cancers, whereas period effects were more variable. No effect of time period was observed in studies of breast, bladder, and oral cavity cancers. Age-specific prevalence of obesity, current smoking, HPV, and HCV also varied by birth cohort, which generally paralleled cancer incidence and mortality rates.

SUMMARY

We observed strong cohort effects across multiple cancer types and less consistent evidence supporting the effect of time period. Birth cohort effects point to exposures early in life - or accumulated across the life course - that increase risk of cancer. Birth cohort effects also illustrate the importance of reconsidering the timing and duration of well-established risk factors to identify periods of exposure conferring the greatest risk.

Trends in incidence, mortality and survival in women with breast cancer from 1985 to 2012 in Granada, Spain: a population-based study

BACKGROUND

The incidence of breast cancer has increased since the 1970s. Despite favorable trends in prognosis, the role of changes in clinical practice and the introduction of screening remain controversial. We examined breast cancer trends to shed light on their determinants.

METHODS

Data were obtained for 8502 new cases of breast cancer in women between 1985 and 2012 from a population-based cancer registry in Granada (southern Spain), and for 2470 breast cancer deaths registered by the Andalusian Institute of Statistics. Joinpoint regression analyses of incidence and mortality rates were obtained. Observed and net survival rates were calculated for 1, 3 and 5 years. The results are reported here for overall survival and survival stratified by age group and tumor stage.

RESULTS

Overall, age-adjusted (European Standard Population) incidence rates increased from 48.0 cases × 100,000 women in 1985-1989 to 83.4 in 2008-2012, with an annual percentage change (APC) of 2.5% (95%CI, 2.1-2.9) for 1985-2012. The greatest increase was in women younger than 40 years (APC 3.5, 95%CI, 2.4-4.8). For 2000-2012 the incidence trend increased only for stage I tumors (APC 3.8, 95%CI, 1.9-5.8). Overall age-adjusted breast cancer mortality decreased (APC - 1, 95%CI, - 1.4 - - 0.5), as did mortality in the 50-69 year age group (APC - 1.3, 95%CI, - 2.2 - - 0.4). Age-standardized net survival increased from 67.5% at 5 years in 1985-1989 to 83.7% in 2010-2012. All age groups younger than 70 years showed a similar evolution. Five-year net survival rates were 96.6% for patients with tumors diagnosed in stage I, 88.2% for stage II, 62.5% for stage III and 23.3% for stage IV.

CONCLUSIONS

Breast cancer incidence is increasing - a reflection of the evolution of risk factors and increasing diagnostic pressure. After screening was introduced, the incidence of stage I tumors increased, with no decrease in the incidence of more advanced stages. Reductions were seen for overall mortality and mortality in the 50-69 year age group, but no changes were found after screening implementation. Survival trends have evolved favorably except for the 70-84 year age group and for metastatic tumors.

Breast cancer incidence: Decreasing trend in large tumours in women aged 50-74

Objective A decrease in advanced breast cancer incidence is considered an early indicator of breast cancer mortality reduction in a screening programme. We describe trends in breast cancer incidence according to tumour size and age in three French administrative areas, where an organized screening programme was implemented during the 1990s. Methods Our study included all 28,092 invasive breast cancers diagnosed from 2000 to 2010 in women living in three areas (Hérault, Isère, Loire-Atlantique). Age, year of diagnosis, and size of tumour at diagnosis was provided by the three area cancer registries. Poisson regression models were fitted to estimate changes in incidence over time, after adjustment for age and administrative area. Results From 2000 to 2010, the incidence rate of large (tumour size >20 mm) breast cancer linearly decreased in women aged 50-74 (target age of the screening programme) from 108.4 to 84.1/100,000 (annual percent change = -1.9%, p < 0.001). No change in large breast cancer incidence rate was found in women aged 20-49, or older than 74. Conclusions A decreasing trend in incidence of large tumour size breast cancer in the target age of the screening programme is demonstrated for the first time in France. The overall 20.9% linear decrease over 11 years in these three areas is encouraging and should be closely monitored and extended to other areas of France, where the screening programme was generally implemented only in 2004.

The contribution of mammography screening to breast cancer incidence trends in the United States: an updated age-period-cohort model

BACKGROUND

The impact of screening mammography on breast cancer incidence is difficult to disentangle from cohort- and age-related effects on incidence.

METHODS

We developed an age-period-cohort model of ductal carcinoma in situ (DCIS) and invasive breast cancer incidence in U.S. females using cancer registry data. Five functions were included in the model to estimate stage-specific effects for age, premenopausal birth cohorts, postmenopausal birth cohorts, period (for all years of diagnosis), and a mammography period effect limited to women ages ≥ 40 years after 1982. Incidence with and without the mammography period effect was calculated.

RESULTS

More recent birth cohorts have elevated underlying risk compared with earlier cohorts for both pre- and postmenopausal women. Comparing models with and without the mammography period effect showed that overall breast cancer incidence would have been 23.1% lower in the absence of mammography in 2010 (95% confidence intervals, 18.8-27.4), including 14.7% (9.5-19.3) lower for invasive breast cancer and 54.5% (47.4-59.6) lower for DCIS. Incidence of distant-staged breast cancer in 2010 would have been 29.0% (13.1-48.1) greater in the absence of mammography screening.

CONCLUSIONS

Mammography contributes to markedly elevated rates of DCIS and early-stage invasive cancers, but also contributes to substantial reductions in the incidence of metastatic breast cancer.

IMPACT

Mammography is an important tool for reducing the burden of breast cancer, but future work is needed to identify risk factors accounting for increasing underlying incidence and to distinguish between indolent and potentially lethal early-stage breast cancers that are detected via mammography.

Escalating burden of breast cancer in southern Thailand: analysis of 1990-2010 incidence and prediction of future trends

BACKGROUND

Thailand is undergoing an epidemiologic transition, with decreasing incidence of infectious diseases and increasing rates of chronic conditions, including cancer. Breast cancer has the highest incidence rates among females both in the southern region Thailand and throughout Thailand. However, there is a lack of research on the epidemiology of this and other cancers.

METHODS

Here we use cancer incidence data from the Songkhla Cancer Registry to characterize and analyze the incidence of breast cancer in Southern Thailand. We use joinpoint analysis, age-period-cohort models and nordpred analysis to investigate the incidence of breast cancer in Southern Thailand from 1990 to 2010 and project future trends from 2010 to 2029.

RESULTS

We found that age-adjusted breast cancer incidence rates in Southern Thailand increased by almost 300% from 1990 to 2010 going from 10.0 to 27.8 cases per 100,000 person-years. Both period and cohort effects played a role in shaping the increase in incidence. Three distinct incidence projection methods consistently suggested that incidence rates will continue to increase in the future with incidence for women age 50 and above increasing at a higher rate than for women below 50.

CONCLUSIONS

To date, this is the first study to examine Thai breast cancer incidence from a regional registry. This study provides a basis for future planning strategies in breast cancer prevention and to guide hypotheses for population-based epidemiologic research in Thailand.

Immediate and delayed effects of mammographic screening on breast cancer mortality and incidence in birth cohorts

BACKGROUND

Trend studies investigating the impact of mammographic screening usually display age-specific mortality and incidence rates over time, resulting in an underestimate of the benefit of screening, that is, mortality reduction, and an overestimate of its major harmful effect, that is, overdiagnosis. This study proposes a more appropriate way of analysing trends.

METHODS

Breast cancer mortality (1950-2009) and incidence data (1975-2009) were obtained from Statistics Netherlands, 'Stg. Medische registratie' and the National Cancer Registry in the Netherlands for women aged 25-85 years. Data were visualised in age-birth cohort and age-period figures.

RESULTS

Birth cohorts invited to participate in the mammographic screening programme showed a deflection in the breast cancer mortality rates within the first 5 years after invitation. Thereafter, the mortality rate increased, although less rapidly than in uninvited birth cohorts. Furthermore, invited birth cohorts showed a sharp increase in invasive breast cancer incidence rate during the first 5 years of invitation, followed by a moderate increase during the following screening years and a decline after passing the upper age limit.

CONCLUSION

When applying a trend study to estimate the impact of mammographic screening, we recommend using a birth cohort approach.

Age Interactions in Breast Cancer: An Analysis of a 10-Year Multicentre Study in China

OBJECTIVES: The effects of age at diagnosis on the clinical characteristics of breast cancer and trends over time were investigated in Chinese women. METHODS: Data from 4211 women with pathologically confirmed primary breast cancer collected between 1999 and 2008 for a multicentre retrospective study were analysed according to age at diagnosis. RESULTS: Age at diagnosis ranged from 21 to 86 years, with a mean of 48.7 years, and was shown to be significantly related to tumour size, lymph node status, hormone receptor status and human growth factor receptor-2 status, but not to pathological type or tumour, node, metastasis stage. The age-corrected proportion of patients aged 50 – 64 years at diagnosis increased significantly between 1999 and 2008. There was a significant difference in the age-corrected distribution of age at diagnosis in China compared with Western countries. CONCLUSIONS: Age at diagnosis is related to the clinical and pathological characteristics of breast cancer. The age at diagnosis in China increased over the decade from 1999 to 2008, but is still lower than in Western countries.