Cancer survival by stage at diagnosis in Wales,

Transcription

1 Cancer survival by stage at diagnosis in Wales, Welsh Cancer Intelligence and Surveillance Unit Latest available one-year net cancer survival by stage at diagnosis official statistics for Wales for diagnosis years 2011 to 2014, by cancer type, sex and area disadvantage Official statistics Published 29 March 2018 Responsible statistician Rebecca Thomas Telephone Cancer survival by stage at diagnosis in Wales,

2 Contents Things you should know What explains the differences in survival by stage at diagnosis between different types of cancer? For most types of cancer, survival decreases as stage at diagnosis becomes later - the gradient of the decrease from earlier to later stages varies considerably between different cancer types Men have better survival than women in later or unknown stages at diagnosis for many cancers, except for lung cancer and melanoma For lung cancer cases diagnosed at stage one, survival decreases steeply as the level of area disadvantage increases Early stage breast cancer one-year survival is universally high, with very little variation between areas of increasing disadvantage For stages one to three, and cases of unknown stage, people with bowel (colorectal) cancer living in areas of increasing disadvantage tend to have increasingly lower survival rates 2 Cancer survival by stage at diagnosis in Wales,

3 Things you should know This is the first time we have ever released national population based one-year net cancer survival figures by stage at diagnosis. Net cancer survival Net survival represents the survival of adult cancer patients (aged years) if they only died from cancer-related causes. Net survival is suitable for comparison of survival between different time periods and populations, as the effect of non-cancer death rates is removed. In this commentary when we refer to survival or one-year survival, we always mean one-year net cancer survival. In this commentary, the survival calculations are NOT adjusted ( standardised ) for the different age-structures of populations over time. Agestandardisation was not possible due to the distribution of cases by cancer type, age and stage at diagnosis being too small at some levels, particularly in the age band years. 95% confidence intervals A confidence interval quantifies the level of uncertainty in a measurement or estimate. A 95% confidence interval is the range of values within which we can be 95% sure that the true value of a statistical measure for the whole population lies, rather than being a chance finding. Confidence intervals will be wider when there are few numbers of staged cases. Statistical significance If a difference in the survival rates between populations is statistically significant, it means that the difference is unlikely to have occurred due to chance alone. We can be more confident that we are observing a true difference. In this commentary we use the conventional arbitrary cut-off of less than 5% chance to mean statistically significant, as indicated by 95% confidence intervals that do not overlap. Just because a difference is statistically significant does not necessarily mean that it is large or important that can depend on our judgement and many other things. Multiple testing occurs when we conduct more than one comparison test for statistical significance. To allow for multiple testing, 99% confidence intervals are sometimes reported. However, multiple testing has not been taken into account in this report and so one in 20 tests will be statistically significant by chance alone. Breast cancer refers to female breast cancer only. 3 Cancer survival by stage at diagnosis in Wales,

4 Melanoma refers to melanoma of the skin only (e.g. not of the retina). Stage at diagnosis Stage at diagnosis refers to the size and extent of a cancer and if it has spread from where it originated at the time of diagnosis. There are various staging systems, the most widely used is the Tumour, Node, Metastasis (TNM) system which summarises cancer from stage one to four; stage one indicates that the cancer is small and has not spread anywhere; stage four indicates the cancer has spread to at least one other body organ. Stage one and stage two cancers are referred to as early stage. Stage three and stage four cancers are referred to as late stage. Unknown stage There are several reasons why a cancer is sometimes recorded as unknown stage in the cancer registry. Some cancers cannot be staged using TNM (e.g. brain cancers). Furthermore, due to some historic data, system and coding issues, some cancer sitespecific staging classifications have not been captured in the national cancer registry at the Welsh Cancer Intelligence and Surveillance Unit during the diagnosis period of this analysis (e.g. haematological cancers). Since 2015, this has improved. Of the cancer sites that could potentially be staged, the stage at diagnosis may be unknown for some of the following reasons: Cancer registration system limitations Insufficient clinical data received to be able to derive cancer registry stage Exchange of data on cancer patients living in Wales but diagnosed or treated in England often did not include staging data until recently Patients might be too ill or turn down diagnostic tests to allow clinical staging A high proportion of unknown stage at diagnosis can cause difficulties with the interpretation of survival rates, particularly when comparing across time periods and cancer types. Cancer survival in Wales We have published the latest available one-year and five-year net cancer survival in Wales (not by stage at diagnosis) as official statistics in September 2017 in both agestandardised and unstandardised forms. 4 Cancer survival by stage at diagnosis in Wales,

5 Cancer incidence by stage at diagnosis in Wales In November 2017, we published as official statistics the latest available incidence of common cancers in Wales, broken down by the numbers and proportion of each diagnosed in stages one to four and unknown stage. Cancer registry data quality Further information about cancer registry data completeness and quality can be found here Cancer type definitions and coding Further information about the definitions of cancer sites can be found here Why are some types of cancer included or excluded in this analysis? In some breakdowns of analysis, not all cancer types are included due to the small numbers of cases or deaths involved. Such small numbers do not allow meaningful survival analysis. For this reason, when analysing survival by stage by area disadvantage fifths, only breast, bowel and lung cancer can be shown. Why is this analysis only at the national Wales geographic level? We understand that analyses at sub-national level are of great value. However, the development of a new statistical method, in collaboration with other UK country cancer registries which will allow intra-uk comparisons in future - is still ongoing. We are working with Public Health England so that the method can be used at smaller areas for future publications very soon. What are the UK comparisons? Historic UK country cancer registry comparisons up to the 2014 year of diagnosis are not possible due to the differences in the method and time periods that each individual country has examined to date. England has calculated age standardised net survival by individual year of diagnosis from 2012 to ( sanddiseases/datasets/oneyearnetcancersurvivalforbladderbreastcolorectalkidneylungmel anomaovaryprostateanduterusbystageatdiagnosis) 5 Cancer survival by stage at diagnosis in Wales,

6 Northern Ireland has publish age standardised net survival by stage at diagnosis data (where possible) for the years combined. What are the international comparisons? Many ongoing international studies (e.g. CONCORD, EUROCARE, ICBP) that involve the Welsh Cancer Intelligence and Surveillance Unit regularly compare survival between participating countries for many types of cancer. However, few regularly publish stage at diagnosis comparisons, and only rarely survival by each stage. One analysis of the first ICBP study suggested that at the time, Wales and other UK countries tended to have later stage at diagnosis compared to many other high-income countries with comparable health systems. For some cancers, the survival for each stage also tended to be lower compared to other such countries. However, this information is now quite old and further survival by stage international analyses based on more recent years of diagnosis are expected within the next one to two years. Policy context The key policy context for improving cancer control in Wales is the Welsh Government s refreshed Cancer Delivery Plan Cancer survival by stage at diagnosis in Wales,

7 What explains the differences in survival by stage at diagnosis between different types of cancer? One reason is that the proportion of unknown stage at diagnosis varies from cancer to cancer. Although it is likely that the unknown stage groups of cancer include many cases that are probably late stage, it is clear that the unknown group is actually a mixture of stages. It is also likely that for each cancer type the proportions of each actual stage in the unknown group will differ. Where survival for unknown stage is higher than survival for stage four for all the cancer types, this suggests that the unknown groups do not just include late stage cancer cases. Further information about cancer registry data completeness and quality can be found here Another reason underlying the observed differences in survival by stage is that the number of people with different cancers may be made-up of different age groups, and have different proportions of men and women. Both these characteristics are known major influences on cancer survival. Ideally, we would have adjusted for age differences, but age-standardisation was not possible. When the total number of cancer cases was broken down into different types of cancer, and then into each of the stages at diagnosis, and then into age-groups, there were often too few cases to allow calculations, particularly in the age band years. Liver cancer and mesothelioma show an irregular trend across the stages which is due to the small numbers of cases and deaths at each stage. Different cancer types behave biologically in different ways, which affects not only overall survival, but also the survival from each stage at diagnosis. 7 Cancer survival by stage at diagnosis in Wales,

8 After diagnosis, for each particular stage, access to cost effective treatments and care, presence of other health conditions alongside the cancer and someone s general health when they develop cancer, can also affect survival at each stage. Other influences on survival at each stage that can vary for different cancers can include socially determined factors such as smoking, obesity, alcohol consumption, and physical inactivity, for example. For most types of cancer, survival decreases as stage at diagnosis becomes later - the gradient of the decrease from earlier to later stages varies considerably between different cancer types Table 1: Unstandardised one-year net cancer survival (%) by stage at diagnosis in Wales, all persons, for diagnosis years , ordered by stage one survival Cancer type Stage 1 Stage 2 Stage 3 Stage 4 Unknown stage All stages Prostate Female breast Thyroid & endocrine Melanoma Larynx Head & neck Ovary Uterus Oral & oropharynx Cervix Kidney Urinary tract exc bladder Colon Bowel (Colorectal) Rectum Oesophagus Bladder Stomach Lung Mesothelioma Pancreas Liver Source: Welsh Cancer Intelligence and Surveillance Unit's National Cancer Registry 8 Cancer survival by stage at diagnosis in Wales,

9 For most types of cancer, one-year survival decreases as stage at diagnosis becomes later - from stage one through to stages two, three and four. gradient of the decrease from earlier to later stages varies considerably between different cancer types. The Breast cancer and cancers of the larynx and prostate, as well as melanoma, have the highest stage one survival. Lung cancer, mesothelioma, and pancreas and liver cancers have the lowest stage one survival. For most of the cancer types we have included, the largest decrease in survival occurred moving from stage three to stage four. For example, survival from prostate cancer remained at 100% for stages one to three, and then fell to 84.1% for stage four. Bowel (colorectal) cancer showed a large reduction in survival between stages three and four, falling from 87.6% to 38.8%. For kidney cancer, stage three survival remained relatively high at 92.5%, but stage four survival fell considerably to 30.7%. However, for some cancers, survival fell quite markedly after stage one at diagnosis. For example, for oesophageal cancer, large falls in survival occurred moving from each stage to the next. It had the largest decrease in survival between stages one and four; falling 78.3 percentage points from 94.5% for stage one, to 16.2% for stage four. Survival from stage one pancreatic and liver cancer was lower than the stage four survival of several other cancer types such as breast, laryngeal, and prostate cancers. 9 Cancer survival by stage at diagnosis in Wales,

10 Men have better survival than women in later or unknown stages at diagnosis for many cancers, except for lung cancer and melanoma Our previous publication Cancer Survival in Wales showed that for most non-sex specific cancers, one-year net survival was higher in men than in women, with the notable exception of lung cancer, as well as melanoma. This latest survival by stage analysis shows that the differences tend to be greatest in the later or unknown stages at diagnosis, for example, for cancers of the bowel (colorectal), bladder, kidney, and urinary tract (excluding bladder). In particular, stage four survival for rectal cancer is statistically significantly higher in men (51.4%) than in women (37.0%). Unknown stage survival for bladder cancer is also statistically significantly higher in men (72.4%) than in women (54.6%). However, for stomach cancer, there is non-significant higher survival in men in stages two, three and four. Lung cancer survival is higher in women than men for stages two and three, and statistically significantly higher in stage four (16.3% for women, 11.6% for men). 10 Cancer survival by stage at diagnosis in Wales,

11 Figure 1: Rectal cancer unstandardised one-year net survival (%) by stage at diagnosis and sex in Wales, for diagnosis years Men Women Men Women Men Women Men Women Men Women Men Women Stage 1 Stage 2 Stage 3 Stage 4 Unknown stage All stages Source: Welsh Cancer Intelligence and Surveillance Unit's National Cancer Registry 11 Cancer survival by stage at diagnosis in Wales,

12 Figure 2: Bladder cancer unstandardised one-year net survival (%) by stage at diagnosis and sex in Wales, for diagnosis years Men Women Men Women Men Women Men Women Men Women Men Women Stage 1 Stage 2 Stage 3 Stage 4 Unknown stage All stages Source: Welsh Cancer Intelligence and Surveillance Unit's National Cancer Registry 12 Cancer survival by stage at diagnosis in Wales,

13 Figure 3: Lung cancer unstandardised one-year net survival (%) by stage at diagnosis and sex in Wales, for diagnosis years Men Women Men Women Men Women Men Women Men Women Men Women Stage 1 Stage 2 Stage 3 Stage 4 Unknown stage All stages Source: Welsh Cancer Intelligence and Surveillance Unit's National Cancer Registry 13 Cancer survival by stage at diagnosis in Wales,

14 For lung cancer cases diagnosed at stage one, survival decreases steeply as the level of area disadvantage increases For lung cancer, there is no statistically significant all-stage survival gradient between worsening area disadvantage fifths. By stage at diagnosis, there is no area disadvantage gradient for lung cancer for stages two, three, four and unknown. The majority of cases are diagnosed in these stages. However, for the minority of all lung cancer cases diagnosed in stage one, survival decreases steeply as area disadvantage increases. This trend is statistically significant, decreasing from almost 90% in the least disadvantaged fifth of areas to 72.1% in the most disadvantaged fifth. Figure 4: Lung cancer unstandardised one-year net survival (%) by stage at diagnosis and area disadvantage in Wales, for diagnosis years Stage 1 Stage 2 Stage 3 Stage 4 Unknown All stages Source: Welsh Cancer Intelligence and Surveillance Unit's National Cancer Registry 14 Cancer survival by stage at diagnosis in Wales,

15 Early stage breast cancer one-year survival is universally high, with very little variation between areas of increasing disadvantage The all-stage survival gradient by fifths of area disadvantage is small for breast cancer. Figure 5: Breast cancer unstandardised one-year net survival (%) by stage at diagnosis and area disadvantage in Wales, for diagnosis years Stage 1 Stage 2 Stage 3 Stage 4 Unknown All stages Source: Welsh Cancer Intelligence and Surveillance Unit's National Cancer Registry Early stage breast cancer one-year survival is universally high, with very little variation between areas of increasing disadvantage. For stage three breast cancer, women living in the least disadvantaged fifth of areas have a survival of 97.3%, compared to 88.7% in the most disadvantaged fifth, with a statistically significant gradient. There are few stage four breast cancer cases; therefore, it is difficult to detect any gradient in survival between areas of different degrees of disadvantage. There is no clear gradient in the unknown stage cases. 15 Cancer survival by stage at diagnosis in Wales,

16 For stages one to three, and cases of unknown stage, people with bowel (colorectal) cancer living in areas of increasing disadvantage tend to have increasingly lower survival rates Figure 6: Bowel (colorectal) cancer unstandardised one-year net survival (%) by stage at diagnosis and area disadvantage in Wales, for diagnosis years Stage 1 Stage 2 Stage 3 Stage 4 Unknown All stages Source: Welsh Cancer Intelligence and Surveillance Unit's National Cancer Registry Unlike lung and breast cancers, for bowel (colorectal) cancer there was a steep gradient of decreasing all-stage survival by increasing area disadvantage. For stages one to three, and cases of unknown stage, there is a tendency for people with bowel cancer in areas of greater disadvantage to have increasingly lower survival rates. The gradient between the most and least disadvantaged areas is statistically significant only for stage three. 16 Cancer survival by stage at diagnosis in Wales,

17 2018 Public Health Wales NHS Trust. Material contained in the data provided to you may be reproduced under the terms of the Open Government Licence (OGL) provided it is done so accurately and is not used in a misleading context. Acknowledgement to Public Health Wales NHS Trust / Welsh Cancer Intelligence and Surveillance Unit to be clearly stated. This study makes use of anonymised data held in the Secure Anonymised Information Linkage (SAIL) system, which is part of the national e-health research infrastructure for Wales. We would like to acknowledge all the data providers who make anonymised data available for research. 17 Cancer survival by stage at diagnosis in Wales,