International burden of cancer deaths and years of life lost from cancer attributable to four major risk factors: a population-based study in Brazil, Russia, India, China, South Africa, the United Kingdom, and United States

Background

We provide a comprehensive view of the impact of alcohol consumption, tobacco smoking, excess body weight, and human papillomavirus (HPV) infection on cancer mortality and years of life lost (YLLs) in Brazil, Russia, India, China, South Africa, the United Kingdom (UK), and United States (US).

Methods

We collected population attributable fractions of the four risk factors from global population-based studies and applied these to estimates of cancer deaths in 2020 to obtain potentially preventable cancer deaths and their 95% confidence intervals (CIs). Using life tables, we calculated the number and age-standardised rates of YLLs (ASYR).

Findings

In Brazil, Russia, India, China, South Africa, the UK, and the US in 2020, an estimated 5.9 million (3.3 million-8.6 million) YLLs from cancer were attributable to alcohol consumption, 20.8 million (17.0 million-24.6 million) YLLs to tobacco smoking, 3.1 million (2.4 million-3.8 million) YLLs to excess body weight, and 4.0 million (3.9 million-4.2 million) YLLs to HPV infection. The ASYR from cancer due to alcohol consumption was highest in China (351.4 YLLs per 100,000 population [95% CI 194.5-519.2]) and lowest in the US (113.5 [69.6-157.1]) and India (115.4 [49.7-172.7). For tobacco smoking, China (1159.9 [950.6-1361.8]) had the highest ASYR followed by Russia (996.8 [831.0-1154.5). For excess body weight, Russia and the US had the highest ASYRs (385.1 [280.6-481.2] and 369.4 [299.6-433.6], respectively). The highest ASYR due to HPV infection was in South Africa (457.1 [453.3-462.6]). ASYRs for alcohol consumption and tobacco smoking were higher among men than women, whereas women had higher ASYRs for excess body weight and HPV infection.

Interpretation

Our findings demonstrate the importance of cancer control efforts to reduce the burden of cancer death and YLLs due to modifiable cancer risk factors and promote the use of YLLs to summarise disease burden.

Funding

Cancer Research UK.

Shifting incidence and survival of epithelial ovarian cancer (1995-2014): A SurvMark-2 study

The aim of the study is to provide a comprehensive assessment of incidence and survival trends of epithelial ovarian cancer (EOC) by histological subtype across seven high income countries (Australia, Canada, Denmark, Ireland, New Zealand, Norway and the United Kingdom). Data on invasive EOC diagnosed in women aged 15 to 99 years during 1995 to 2014 were obtained from 20 cancer registries. Age standardized incidence rates and average annual percentage change were calculated by subtype for all ages and age groups (15-64 and 65-99 years). Net survival (NS) was estimated by subtype, age group and 5-year period using Pohar-Perme estimator. Our findings showed marked increase in serous carcinoma incidence was observed between 1995 and 2014 among women aged 65 to 99 years with average annual increase ranging between 2.2% and 5.8%. We documented a marked decrease in the incidence of adenocarcinoma "not otherwise specified" with estimates ranging between 4.4% and 7.4% in women aged 15 to 64 years and between 2.0% and 3.7% among the older age group. Improved survival, combining all EOC subtypes, was observed for all ages combined over the 20-year study period in all countries with 5-year NS absolute percent change ranging between 5.0 in Canada and 12.6 in Denmark. Several factors such as changes in guidelines and advancement in diagnostic tools may potentially influence the observed shift in histological subtypes and temporal trends. Progress in clinical management and treatment over the past decades potentially plays a role in the observed improvements in EOC survival.

Global burden of colorectal cancer in 2020 and 2040: incidence and mortality estimates from GLOBOCAN

OBJECTIVE

Colorectal cancer (CRC) is the third most common cancer worldwide. The geographical and temporal burden of this cancer provides insights into risk factor prevalence and progress in cancer control strategies. We examine the current and future burden of CRC in 185 countries in 2020 and 2040.

METHODS

Data on CRC cases and deaths were extracted from the GLOBOCAN database for the year 2020. Age-standardised incidence and mortality rates were calculated by sex, country, world region and Human Development Index (HDI) for 185 countries. Age-specific rates were also estimated. The predicted number of cases and deaths in 2040 were calculated based on global demographic projections by HDI.

RESULTS

Over 1.9 million new CRC cases and 930 000 deaths were estimated in 2020. Incidence rates were highest in Australia/ New Zealand and European regions (40.6 per 100 000, males) and lowest in several African regions and Southern Asia (4.4 per 100 000, females). Similar patterns were observed for mortality rates, with the highest observed in Eastern Europe (20.2 per 100 000, males) and the lowest in Southern Asia (2.5 per 100 000, females). The burden of CRC is projected to increase to 3.2 million new cases and 1.6 million deaths by 2040 with most cases predicted to occur in high or very high HDI countries.

CONCLUSIONS

CRC is a highly frequent cancer worldwide, and largely preventable through changes in modifiable risk factors, alongside the detection and removal of precancerous lesions. With increasing rates in transitioning countries and younger adults, there is a pressing need to better understand and act on findings to avert future cases and deaths from the disease.

The preventability of cancer in Europe: A quantitative assessment of avoidable cancer cases across 17 cancer sites and 38 countries in 2020

OBJECTIVE

The aim of this study is to provide an update of the estimated proportion of avoidable cases across European region for cancers associated with modifiable risk factors.

METHODS

Age-standardised incidence rates for 38 European countries in 2020 were derived from GLOBOCAN database. For 17 cancer sites, we estimated the number and proportion of avoidable cancer cases. The mean of the three lowest country-specific incidence (excluding rates of zero) was defined as the attainable rate for each combination of cancer site, sex, and age group. The number and proportion of avoidable cancer cases was calculated as the difference between the country-specific and attainable incidence rates.

RESULTS

Approximately, 697,000 cancer cases (33%) of all cases in men, and 837,000 (44%) in women were potentially avoidable. Lung, colorectal, and female breast cancer contributed the largest avoidable burden from cancer, with a combined 790,000 cases, followed by mesothelioma, melanoma of the skin, laryngeal, and oesophageal cancer as major contributors. Large geographical variations were found in the estimated proportion of avoidable cancer cases by sex.

CONCLUSIONS

A cohesive population-level preventative effort to reduce modifiable cancer risk factors could potentially have considerable impact in reducing the future burden of many cancers in Europe.

Cancer survival in Thailand from 1997 to 2012: Assessing the impact of universal health coverage

BACKGROUND

In recent decades, many countries worldwide have implemented some form of Universal Health Coverage (UHC). We sought to evaluate incidence and survival trends of breast, cervical, and colorectal cancer before and after the implementation of UHC in Thailand.

METHODS

The age-standardized incidence rate and 1- and 5-year net survival (NS) were calculated for five Thai provinces, namely Bangkok, Chiang Mai, Khon Kaen, Lampang, and Songkhla for breast, cervix, and colorectal cancer in three study periods (1997-2012): before, during, and after the implementation of UHC.

RESULTS

The incidence of breast and colorectal cancer has increased over time, while the incidence of cervical cancer has decreased (17.9-29.9, 9.0-13.6, and 19.6-12.3 per 100,000, respectively). Larger proportion of breast cancer were diagnosed with localized stage after UHC implementation compared to the period prior to UHC (31.5 % vs 19.0 %). Overall, The improvement in survival by cancer site varied in magnitude with a 5-year NS increase from 61.3 % to 75.1 % for breast, 55.4-59.5 % for cervical, and 39.9-47.6 % for colorectal cancer. The amount of increase slightly differed across provinces.

CONCLUSION

Rising incidence for breast and colorectal, and declining cervical cancer may partly be attributable to improved awareness and early detection programs. Additionally, improvement in survival may partly be attributable to increased access to healthcare, availability of treatment, and increased access to cancer screening after UHC was implemented. Thus, continued expansion of UHC package on cancer could potentially contribute to further improvement of cancer control in Thailand.

POLICY SUMMARY

This study provides important evidence on the impact of UHC in cancer burden and survival for breast, cervical, and colorectal cancer in Thailand. This study serves as an example for other countries where UHC has been recently implemented and guide policymakers in allocating resources towards UHC and cancer control programs.

Ovarian cancer today and tomorrow: A global assessment by world region and Human Development Index using GLOBOCAN 2020

Ovarian cancer remains to have relatively poor prognosis particularly in low-resourced settings. It is therefore important to continually examine the burden of ovarian cancer to identify areas of disparities. Our study aims to provide an overview of the global burden of ovarian cancer using the GLOBOCAN 2020 estimates by country, world region, and Human Development Index (HDI) levels, as well as the predicted future burden by the year 2040 by HDI. Age-standardized incidence and mortality rates for ovarian cancer in 185 countries were calculated by country, world region, and for the four-tier HDI. The number of new cases and deaths were projected for the year 2040 based on demographic projections by HDI category. Approximately 314 000 new ovarian cancer cases and 207 000 deaths occurred in 2020. There were marked geographic variations in incidence rates, with the highest rates observed in European countries with very high HDI and low rates were found in African countries within the lowest HDI group. Comparable mortality rates were observed across the four-tier HDI. Relative to 2020 estimates, our projection for 2040 indicates approximately 96% and 100% increase in new ovarian cancer cases and deaths, respectively, among low HDI countries compared to 19% and 28% in very high HDI countries. Our study highlights the disproportionate current and future burden of ovarian cancer in countries with lower HDI levels, calling for global action to reduce the burden and inequality of ovarian cancer in access to quality cancer care and treatment.

Pancreatic cancer survival by stage and age in seven high-income countries (ICBP SURVMARK-2): a population-based study

BACKGROUND

The global burden of pancreatic cancer has steadily increased, while the prognosis after pancreatic cancer diagnosis remains poor. This study aims to compare the stage- and age-specific pancreatic cancer net survival (NS) for seven high-income countries: Australia, Canada, Denmark, Ireland, New Zealand, Norway, and United Kingdom.

METHODS

The study included over 35,000 pancreatic cancer cases diagnosed during 2012-2014, followed through 31 December 2015. The stage- and age-specific NS were calculated using the Pohar-Perme estimator.

RESULTS

Pancreatic cancer survival estimates were low across all 7 countries, with 1-year NS ranging from 21.1% in New Zealand to 30.9% in Australia, and 3-year NS from 6.6% in the UK to 10.9% in Australia. Most pancreatic cancers were diagnosed with distant stage, ranging from 53.9% in Ireland to 83.3% in New Zealand. While survival differences were evident between countries across all stage categories at one year after diagnosis, this survival advantage diminished, particularly in cases with distant stage.

CONCLUSION

This study demonstrated the importance of stage and age at diagnosis in pancreatic cancer survival. Although progress has been made in improving pancreatic cancer prognosis, the disease is highly fatal and will remain so without major breakthroughs in the early diagnosis and management.

Cancer incidence and mortality in Australia from 2020 to 2044 and an exploratory analysis of the potential effect of treatment delays during the COVID-19 pandemic: a statistical modelling study

BACKGROUND

Long-term projections of cancer incidence and mortality estimate the future burden of cancer in a population, and can be of great use in informing the planning of health services and the management of resources. We aimed to estimate incidence and mortality rates and numbers of new cases and deaths up until 2044 for all cancers combined and for 21 individual cancer types in Australia. We also illustrate the potential effect of treatment delays due to the COVID-19 pandemic on future colorectal cancer mortality rates.

METHODS

In this statistical modelling study, cancer incidence and mortality rates in Australia from 2020 to 2044 were projected based on data up to 2017 and 2019, respectively. Cigarette smoking exposure (1945-2019), participation rates in the breast cancer screening programme (1996-2019), and prostate-specific antigen testing rates (1994-2020) were included where relevant. The baseline projection model using an age-period-cohort model or generalised linear model for each cancer type was selected based on model fit statistics and validation with pre-COVID-19 observed data. To assess the impact of treatment delays during the COVID-19 pandemic on colorectal cancer mortality, we obtained data on incidence, survival, prevalence, and cancer treatment for colorectal cancer from different authorities. The relative risks of death due to system-caused treatment delays were derived from a published systematic review. Numbers of excess colorectal cancer deaths were estimated using the relative risk of death per week of treatment delay and different durations of delay under a number of hypothetical scenarios.

FINDINGS

Projections indicate that in the absence of the COVID-19 pandemic effects, the age-standardised incidence rate for all cancers combined for males would decline over 2020-44, and for females the incidence rate would be relatively stable in Australia. The mortality rates for all cancers combined for both males and females are expected to continuously decline during 2020-44. The total number of new cases are projected to increase by 47·4% (95% uncertainty interval [UI] 35·2-61·3) for males, from 380 306 in 2015-19 to 560 744 (95% UI 514 244-613 356) in 2040-44, and by 54·4% (95% UI 40·2-70·5) for females, from 313 263 in 2015-19 to 483 527 (95% UI 439 069-534 090) in 2040-44. The number of cancer deaths are projected to increase by 36·4% (95% UI 15·3-63·9) for males, from 132 440 in 2015-19 to 180 663 (95% UI 152 719-217 126) in 2040-44, and by 36·6% (95% UI 15·8-64·1) for females, from 102 103 in 2015-19 to 139 482 (95% UI 118 186-167 527) in 2040-44, due to population ageing and growth. The example COVID-19 pandemic scenario of a 6-month health-care system disruption with 16-week treatment delays for colorectal cancer patients could result in 460 (95% UI 338-595) additional deaths and 437 (95% UI 314-570) deaths occurring earlier than expected in 2020-44.

INTERPRETATION

These projections can inform health service planning for cancer care and treatment in Australia. Despite the continuous decline in cancer mortality rates, and the decline or plateau in incidence rates, our projections suggest an overall 51% increase in the number of new cancer cases and a 36% increase in the number of cancer deaths over the 25-year projection period. This means that continued efforts to increase screening uptake and to control risk factors, including smoking exposure, obesity, physical inactivity, alcohol use, and infections, must remain public health priorities.

FUNDING

Partly funded by Cancer Council Australia.

Tobacco smoking changes during the first pre-vaccination phases of the COVID-19 pandemic: A systematic review and meta-analysis

Background

Globally, tobacco smoking remains the largest preventable cause of premature death. The COVID-19 pandemic has forced nations to take unprecedented measures, including 'lockdowns' that might impact tobacco smoking behaviour. We performed a systematic review and meta-analyses to assess smoking behaviour changes during the early pre-vaccination phases of the COVID-19 pandemic in 2020.

Methods

We searched Medline/Embase/PsycINFO/BioRxiv/MedRxiv/SSRN databases (January-November 2020) for published and pre-print articles that reported specific smoking behaviour changes or intentions after the onset of the COVID-19 pandemic. We used random-effects models to pool prevalence ratios comparing the prevalence of smoking during and before the pandemic, and the prevalence of smoking behaviour changes during the pandemic. The PROSPERO registration number for this systematic review was CRD42020206383.

Findings

31 studies were included in meta-analyses, with smoking data for 269,164 participants across 24 countries. The proportion of people smoking during the pandemic was lower than that before, with a pooled prevalence ratio of 0·87 (95%CI:0·79-0·97). Among people who smoke, 21% (95%CI:14-30%) smoked less, 27% (95%CI:22-32%) smoked more, 50% (95%CI:41%-58%) had unchanged smoking and 4% (95%CI:1-9%) reported quitting smoking. Among people who did not smoke, 2% (95%CI:1-3%) started smoking during the pandemic. Heterogeneity was high in all meta-analyses and so the pooled estimates should be interpreted with caution (I2 >91% and p-heterogeneity<0·001). Almost all studies were at high risk of bias due to use of non-representative samples, non-response bias, and utilisation of non-validated questions.

Interpretation

Smoking behaviour changes during the first phases of the COVID-19 pandemic in 2020 were highly mixed. Meta-analyses indicated that there was a relative reduction in overall smoking prevalence during the pandemic, while similar proportions of people who smoke smoked more or smoked less, although heterogeneity was high. Implementation of evidence-based tobacco control policies and programs, including tobacco cessation services, have an important role in ensuring that the COVID-19 pandemic does not exacerbate the smoking pandemic and associated adverse health outcomes.

Funding

No specific funding was received for this study.

Population-based cancer staging for oesophageal, gastric, and pancreatic cancer 2012-2014: International Cancer Benchmarking Partnership SurvMark-2

Cancer stage at diagnosis is important information for management and treatment of individual patients as well as in epidemiological studies to evaluate effectiveness of health care system in managing cancer patients. Population-based studies to examine international disparities on cancer survival by stage, however, has been challenging due to the lack of international standardization on recording stage information and variation in stage completeness across regions and countries. The International Cancer Benchmarking Partnership (ICBP) previously assessed the availability and comparability of staging information for colorectal, lung, female breast and ovarian cancers. Stage conversion algorithms were developed to aggregate and map all stage information into a single staging system to allow international comparison by stage at diagnosis. In this article, we developed stage conversion algorithms for three additional cancers, namely oesophageal, gastric and pancreatic cancers. We examined all stage information available, evaluated stage completeness, applied each stage conversion algorithm, and assessed the magnitude of misclassification using data from six Canadian cancer registries (Alberta, Manitoba, Newfoundland, Nova Scotia, Prince Edward Island and Saskatchewan). In addition, we discussed five recommendations for registries to improve international cancer survival comparison by stage: (a) improve collection and completeness of staging data; (b) promote a comparable definition for stage at diagnosis; (c) promote the use of a common stage classification system; (d) record versions of staging classifications and (e) use multiple data sources for valid staging data.

Joint IARC/NCI International Cancer Seminar Series Report: expert consensus on future directions for ovarian carcinoma research

Recently, ovarian cancer research has evolved considerably because of the emerging recognition that rather than a single disease, ovarian carcinomas comprise several different histotypes that vary by etiologic origin, risk factors, molecular profiles, therapeutic approaches and clinical outcome. Despite significant progress in our understanding of the etiologic heterogeneity of ovarian cancer, as well as important clinical advances, it remains the eighth most frequently diagnosed cancer in women worldwide and the most fatal gynecologic cancer. The International Agency for Research on Cancer and the United States National Cancer Institute jointly convened an expert panel on ovarian carcinoma to develop consensus research priorities based on evolving scientific discoveries. Expertise ranged from etiology, prevention, early detection, pathology, model systems, molecular characterization and treatment/clinical management. This report summarizes the current state of knowledge and highlights expert consensus on future directions to continue advancing etiologic, epidemiologic and prognostic research on ovarian carcinoma.

Colon and rectal cancer survival in seven high-income countries 2010-2014: variation by age and stage at diagnosis (the ICBP SURVMARK-2 project)

OBJECTIVES

As part of the International Cancer Benchmarking Partnership (ICBP) SURVMARK-2 project, we provide the most recent estimates of colon and rectal cancer survival in seven high-income countries by age and stage at diagnosis.

METHODS

Data from 386 870 patients diagnosed during 2010-2014 from 19 cancer registries in seven countries (Australia, Canada, Denmark, Ireland, New Zealand, Norway and the UK) were analysed. 1-year and 5-year net survival from colon and rectal cancer were estimated by stage at diagnosis, age and country, RESULTS: (One1-year) and 5-year net survival varied between (77.1% and 87.5%) 59.1% and 70.9% and (84.8% and 90.0%) 61.6% and 70.9% for colon and rectal cancer, respectively. Survival was consistently higher in Australia, Canada and Norway, with smaller proportions of patients with metastatic disease in Canada and Australia. International differences in (1-year) and 5-year survival were most pronounced for regional and distant colon cancer ranging between (86.0% and 94.1%) 62.5% and 77.5% and (40.7% and 56.4%) 8.0% and 17.3%, respectively. Similar patterns were observed for rectal cancer. Stage distribution of colon and rectal cancers by age varied across countries with marked survival differences for patients with metastatic disease and diagnosed at older ages (irrespective of stage).

CONCLUSIONS

Survival disparities for colon and rectal cancer across high-income countries are likely explained by earlier diagnosis in some countries and differences in treatment for regional and distant disease, as well as older age at diagnosis. Differences in cancer registration practice and different staging systems across countries may have impacted the comparisons.

Exploring international differences in ovarian cancer treatment: a comparison of clinical practice guidelines and patterns of care

INTRODUCTION

The International Cancer Benchmarking Partnership demonstrated international differences in ovarian cancer survival, particularly for women aged 65-74 with advanced disease. These findings suggest differences in treatment could be contributing to survival disparities.

OBJECTIVE

To compare clinical practice guidelines and patterns of care across seven high-income countries.

METHODS

A comparison of guidelines was performed and validated by a clinical working group. To explore clinical practice, a patterns of care survey was developed. A questionnaire regarding management and potential health system-related barriers to providing treatment was emailed to gynecological specialists. Guideline and survey results were crudely compared with 3-year survival by 'distant' stage using Spearman's rho.

RESULTS

Twenty-seven guidelines were compared, and 119 clinicians completed the survey. Guideline-related measures varied between countries but did not correlate with survival internationally. Guidelines were consistent for surgical recommendations of either primary debulking surgery or neoadjuvant chemotherapy followed by interval debulking surgery with the aim of complete cytoreduction. Reported patterns of surgical care varied internationally, including for rates of primary versus interval debulking, extensive/'ultra-radical' surgery, and perceived barriers to optimal cytoreduction. Comparison showed that willingness to undertake extensive surgery correlated with survival across countries (rs=0.94, p=0.017). For systemic/radiation therapies, guideline differences were more pronounced, particularly for bevacizumab and PARP (poly (ADP-ribose) polymerase) inhibitors. Reported health system-related barriers also varied internationally and included a lack of adequate hospital staffing and treatment monitoring via local and national audits.

DISCUSSION

Findings suggest international variations in ovarian cancer treatment. Characteristics relating to countries with higher stage-specific survival included higher reported rates of primary surgery; willingness to undertake extensive/ultra-radical procedures; greater access to high-cost drugs; and auditing.

Cervical cancer burden in Latin America and the Caribbean: Where are we?

In May 2018, the World Health Organization (WHO) called for the elimination of cervical cancer. To monitor this initiative, we examined cervical cancer incidence and mortality in the Latin America and Caribbean (LAC) region using GLOBOCAN 2018, Cancer Incidence in Five Continents Series, and the WHO Mortality Database. We estimated the number of cases and age-standardized rates (ASRs) for cervical cancer incidence and mortality for 2018. We also presented the ASRs for recorded cervical cancer incidence from the period 2008 to 2012. We calculated annual rates and analyzed trends in cervical cancer incidence and mortality for all ages combined and for the following age groups: 0-29, 30-49, 50-64 and 65+. Finally, we calculated the estimated average annual percentage change in incidence and mortality rates for the past 10 years. In 2018, an estimated 56,000 new cervical cancer cases and 28,000 cervical cancer deaths occurred among women in LAC with great variations between subregions and countries/territories. Overall, trends in cervical cancer incidence and mortality have decreased over the past decade; however, the rates are still above the elimination threshold of 4 per 100,000 in most LAC countries/territories. Despite the encouraging trends observed, achieving the elimination of cervical cancer in the region still requests substantial political commitment and economic effort. Population-based cancer registries are critical in monitoring the elimination initiative.

Exploring variations in ovarian cancer survival by age and stage (ICBP SurvMark-2): A population-based study

OBJECTIVE

The study aims to evaluate the differences in ovarian cancer survival by age and stage at diagnosis within and across seven high-income countries.

METHODS

We analyzed data from 58,161 women diagnosed with ovarian cancer during 2010-2014, followed until 31 December 2015, from 21 population-based cancer registries in Australia, Canada, Denmark, Ireland, New Zealand, Norway, and United Kingdom. Comparisons of 1-year and 3-year age- and stage-specific net survival (NS) between countries were performed using the period analysis approach.

RESULTS

Minor variation in the stage distribution was observed between countries, with most women being diagnosed with 'distant' stage (ranging between 64% in Canada and 71% in Norway). The 3-year all-ages NS ranged from 45 to 57% with Australia (56%) and Norway (57%) demonstrating the highest survival. The proportion of women with 'distant' stage was highest for those aged 65-74 and 75-99 years and varied markedly between countries (range:72-80% and 77-87%, respectively). The oldest age group had the lowest 3-year age-specific survival (20-34%), and women aged 65-74 exhibited the widest variation across countries (3-year NS range: 40-60%). Differences in survival between countries were particularly stark for the oldest age group with 'distant' stage (3-year NS range: 12% in Ireland to 24% in Norway).

CONCLUSIONS

International variations in ovarian cancer survival by stage exist with the largest differences observed in the oldest age group with advanced disease. This finding endorses further research investigating international differences in access to and quality of treatment, and prevalence of comorbid conditions particularly in older women with advanced disease.

The influence of birth cohort and calendar period on global trends in ovarian cancer incidence

Ovarian cancer is the eighth most common cancer in women worldwide and incidence rates vary markedly by world region. Our study provides a comprehensive overview of ovarian cancer incidence trends globally, examining the influence of birth cohort and period of diagnosis on changing risk. We presented current patterns and trends of ovarian cancer incidence until 2012 using data from successive volumes of Cancer Incidence in Five Contents. The incidence of ovarian cancer is highest in northern and eastern European countries and in northern America. Declining trends were observed in most countries with the exception of a few central and eastern Asian countries. Marked declines were seen in Europe and North America for women aged 50-74 where rates have declined up to 2.4% (95% CI: -3.9, -0.9) annually in Denmark (DNK) over the last decade. Additionally, declines in the incidence rate ratio (IRR) were observed for generations born after the 1930s, with an additional strong period effect seen around 2000 in United States and DNK. In contrast, IRRs increased among younger generations born after the 1950s in Japan and Belarus. Overall, the favorable trends in ovarian cancer incidence is likely due to the increase use of oral contraceptive pills, and changes in the prevalence of other reproductive risk and protective factors for ovarian cancer over the years studied. Changes in disease classifications and cancer registry practices may also partially contribute to the variation in ovarian cancer incidence rates. Thus, continuous cancer surveillance is essential to detect the shifting patterns of ovarian cancer.

Changes in colorectal cancer incidence in seven high-income countries: a population-based study

BACKGROUND

The overall incidence of colorectal cancer is decreasing in many high-income countries, yet analyses in the USA and other high-income countries such as Australia, Canada, and Norway have suggested increasing incidences among adults younger than 50 years. We aimed to examine longitudinal and generational changes in the incidence of colon and rectal cancer in seven high-income countries.

METHODS

We obtained data for the incidence of colon and rectal cancer from 21 population-based cancer registries in Australia, Canada, Denmark, Norway, New Zealand, Ireland, and the UK for the earliest available year until 2014. We used age-period-cohort modelling to assess trends in incidence by age group, period, and birth cohort. We stratified cases by tumour subsite according to the 10th edition of the International Classification of Diseases. Age-standardised incidences were calculated on the basis of the world standard population.

FINDINGS

An overall decline or stabilisation in the incidence of colon and rectal cancer was noted in all studied countries. In the most recent 10-year period for which data were available, however, significant increases were noted in the incidence of colon cancer in people younger than 50 years in Denmark (by 3·1%), New Zealand (2·9%), Australia (2·9%), and the UK (1·8%). Significant increases in the incidence of rectal cancer were also noted in this age group in Canada (by 3·4%), Australia (2·6%), and the UK (1·4%). Contemporaneously, in people aged 50-74 years, the incidence of colon cancer decreased significantly in Australia (by 1·6%), Canada (1·9%), and New Zealand (3·4%) and of rectal cancer in Australia (2·4%), Canada (1·2%), and the UK (1·2%). Increases in the incidence of colorectal cancer in people younger than 50 years were mainly driven by increases in distal (left) tumours of the colon. In all countries, we noted non-linear cohort effects, which were more pronounced for rectal than for colon cancer.

INTERPRETATION

We noted a substantial increase in the incidence of colorectal cancer in people younger than 50 years in some of the countries in this study. Future studies are needed to establish the root causes of this rising incidence to enable the development of potential preventive and early-detection strategies.

FUNDING

Canadian Partnership Against Cancer, Cancer Council Victoria, Cancer Institute New South Wales, Cancer Research UK, Danish Cancer Society, National Cancer Registry Ireland, the Cancer Society of New Zealand, NHS England, Norwegian Cancer Society, Public Health Agency Northern Ireland, Scottish Government, Western Australia Department of Health, and Wales Cancer Network.