Introduction:
This measure comprises national data on relative survival by stage at diagnosis for colorectal cancer
Stage at diagnosis indicates the extent to which a cancer has spread at diagnosis. It is an important prognostic factor for cancer outcomes. It also provides contextual information for interpreting cancer outcomes, including survival, at a population level.1
Relative survival refers to the probability of being alive for a given amount of time after diagnosis, compared with survival of the general population. Observed survival refers to the overall proportion of people who are alive following a specified amount of time (e.g. 1 year, 3 years or 5 years) after diagnosis of cancer. In this report, ‘survival’ refers to relative survival unless otherwise stated. Examining survival by stage at diagnosis provides insights into how survival outcomes differ depending on extent of cancer spread at diagnosis.
To provide a better understanding of cancer stage at diagnosis at the population-level, Business Rules were developed to collect national data on Registry-derived stage (RD-stage) at diagnosis using data sources that are routinely accessible to all population-based cancer registries. RD-stage is defined for invasive tumours only. More information on the capture and distribution of RD-stage at diagnosis can be accessed through the following measures:
The following sections of this report present 1, 3 and 5-year relative survival by RD-stage at diagnosis (hereafter referred to as ‘stage’) for people diagnosed with colorectal cancer in 2011. Data on survival by stage at diagnosis for other cancer types can be accessed through the following measures:
More information about data sources, methods for collection, and guidance for interpreting the data can be found in the ‘About the Data’ tab.
Charts
About this measure
This measure presents national survival by stage at diagnosis data for colorectal cancer in Australia using data sources that are routinely accessible to all cancer registries. To date, RD-stage has been collected for a single index year (2011) as this represented the most up-to-date cancer incidence data for which 5-year survival by stage could be reported in Australia up to 2016. In collaboration with Cancer Australia, the population-based cancer registries (PBCRs), and the Australasian Association of Cancer Registries (AACR), the Australian Institute of Health and Welfare (AIHW) has combined the newly collected information on RD-stage, cancer incidence from the Australian Cancer Database (ACD), and mortality from the National Death Index (NDI).
Prior to 2018 the lack of high quality national cancer staging data had been an identified gap in our data knowledge in Australia. As part of the Stage, Treatment and Recurrence (STaR) project, Cancer Australia has worked with PBCRs and AACR to develop nationally-standardised methodologies for collecting stage at diagnosis data. This work has initially focussed on the top five incident cancers (female breast, colorectal, lung, prostate cancer, and melanoma) for population-level reporting purposes.
Cancer Australia supported the Cancer Council Victoria (CCV) in developing Business Rules for the collection of national cancer stage at diagnosis for invasive tumours based on the Tumour, Node, and Metastases (TNM) staging system as developed and maintained by the American Joint Committee on Cancer (AJCC, 7th edition) in collaboration with the International Union for Cancer Control (UICC). The TNM Staging System is based on the extent of the tumour (T), the extent of spread to the lymph nodes (N), and the presence of metastasis (M). As each cancer type has its own classification system, letters and numbers do not always mean the same thing for every kind of cancer. Once the T, N, and M are determined, they are combined, and an overall stage of 0, I, II, III, IV is assigned.2
Using these Business Rules, all Australian PBCRs have derived RD-stage at diagnosis using data sources that are routinely accessible to all cancer registries. RD-stage at diagnosis is defined as the best estimate of summary TNM stage at diagnosis that can be derived nationally by Australian cancer registries from the data sources available to them. Its purpose will be for population-based analyses, not clinical applications.
RD-stage has the following values:
- Stage 1 (equivalent to TNM stage I; Early stage)
- Stage 2 (equivalent to TNM stage II; Early stage)
- Stage 3 (equivalent to TNM stage III; Locally advanced)
- Stage 4 (equivalent to TNM stage IV; Metastatic)
- Stage unknown
- Stage not applicable (including tumours with morphologies not eligible for TNM and tumours with no histological confirmation) – These have been excluded for the purpose of this analysis.
Upcoming releases for stage at diagnosis data:
Cancer Australia has also supported the development of a set of complementary Business Rules for deriving cancer stage at diagnosis for 16 paediatric (childhood) cancer types. Initial data on childhood cancer stage at diagnosis were released for the first time in Australia on the NCCI website in August 2018. These initial data are available in the following measures:
- Distribution of childhood cancer stage
- Five-year observed survival by stage at diagnosis for childhood cancers
The initial data presented for childhood cancers are for the years 2006-2010. The collection of these data for the remaining period of 2011-2014 is still in progress and more detailed data for the entire period of 2006-2014 will be available when this is finalised in 2019.
Current status
Survival by stage at diagnosis indicates the probability of surviving for a specified time-period depending on the extent of the cancer (stage) at diagnosis. To assist in interpreting the data, some of the findings in the following sections are grouped into:
- Early stage cancers (stage 1 and 2) – restricted to the local area of origin of the cancer;
- Locally advanced cancers (stage 3) – cancers which have spread locally; and
- Metastatic cancers (stage 4) – cancers which have spread to distant sites.
The stage at diagnosis for colorectal cancer has been derived from data sources that are routinely accessible to all population-based cancer registries. These data are intended to be used for broad population-based analyses, and not to guide care of an individual.
The data showed that for colorectal cancers diagnosed in 2011, cases were relatively evenly distributed across each stage category:
- Early stage cancers (stage 1 and 2) accounted for almost half (46%) of incident cases.
- Stage 1 cancers accounted for 22% of cases (3,098 cases);
- Stage 2 cancers accounted for 24% of cases (3,399 cases).
- Locally advanced cancers (stage 3) accounted for 24% of cases (3,299 cases).
- Metastatic cancers (stage 4) accounted for 18% of cases (2,474 cases).
- It was not possible to determine stage at diagnosis for 12% of cases (unknown stage; 1,723 cases).
More information on the distribution of stage at diagnosis can be accessed through the ‘Distribution of cancer stage’ measure.
Relative survival by RD-stage at diagnosis for colorectal cancers diagnosed in 2011
Relative survival for all colorectal cancers
Survival for people diagnosed with colorectal cancer in 2011 generally decreased with increasing time from diagnosis at:
- 86% at 1 year from diagnosis;
- 75% at 3 years from diagnosis;
- 70% at 5 years from diagnosis.
Although these data provide insights into survival for people diagnosed with colorectal cancer, it is also important to examine how survival differs by the extent to which a cancer has spread when first diagnosed.
Relative survival by RD-stage for all colorectal cancers
Examining relative survival by stage at diagnosis showed that survival was high for people diagnosed with early stage colorectal cancers and survival remained high up to 5 years from diagnosis. Cancers diagnosed at stage 3 and 4 had progressively lower survival in subsequent years from diagnosis compared to early stage cancers. Survival by stage at diagnosis is examined in more detail in the following sections.
Relative survival for early stage colorectal cancers (all persons)
For people diagnosed with early stage cancers (stage 1 and 2), survival remained high up to 5 years from diagnosis.
Survival for people diagnosed with:
- Stage 1 cancers was 99% at 1, 3 and 5 years from diagnosis;
- Stage 2 cancers decreased from 96% to 93% between 1 and 3 years from diagnosis. Survival decreased further to 89% at 5 years from diagnosis.
Relative survival for advanced colorectal cancers (all persons)
Survival was lower for people diagnosed with advanced cancers, particularly for cancers diagnosed as metastatic (stage 4). Survival also decreased with increasing time from diagnosis for stage 3 and 4 cancers.
Survival for people diagnosed with:
- Locally advanced cancers (stage 3) decreased from 94% to 79% between 1 and 3 years from diagnosis. Survival decreased further to 71% at 5 years from diagnosis;
- Metastatic cancers (stage 4) decreased from 49% to 23% between 1 and 3 years from diagnosis. Survival decreased further to 13% at 5 years from diagnosis.
Relative survival by stage at diagnosis, sex and age in 2011
Relative survival by sex for colorectal cancers
For colorectal cancer, survival by stage at diagnosis was similar for males and females.
For stage 1 cancers, survival was high (at least 97%) for both males and females at 1, 3 and 5 years from diagnosis.
For stage 2 cancers, survival was similar for males and females at 1 year (96% compared to 97%), 3 years (92% compared to 93%) and 5 years (88% compared to 90%) respectively.
For locally advanced cancers (stage 3), survival was similar for males and females at 1 year (94% compared to 93%), 3 years (80% compared to 78%) and 5 years (71% for both).
For metastatic cancers (stage 4), survival was similar for males and females at 1 year (51% compared to 48%), 3 years (24% compared to 22%) and 5 years (13% compared to 14%).
Relative survival by age for colorectal cancers
The analysis in the following section examines overall patterns in relative survival across age groups where there were sufficient numbers for reporting purposes. The overall trend showed a lower survival with increasing age for cancers diagnosed at stage 3 and 4. Guidance for interpreting the data can be found in the ‘About the Data’ tab.
For stage 1 cancers, survival was similar across all age groups at 1 year (between 98% and 100%), 3 years (between 97% and 99%) and 5 years from diagnosis (between 95% and 100%).
Stage 2 cancers, survival varied across all age groups at 1 year (between 92% and 100%), 3 years (between 90% and 99%), and 5 years from diagnosis (between 84% and 95%).
For locally advanced cancers (stage 3):
- Survival generally decreased with increasing age for people:
- In age groups between 50 and 85 years and over from 99% to 81% at 1 year from diagnosis;
- In age groups between 45 and 85 years and over from 90% to 62% at 3 years from diagnosis;
- In age groups between 45 and 85 years and over from 83% to 56% at 5 years from diagnosis.
For metastatic cancers (stage 4):
- Survival generally decreased with increasing age for people:
- In age groups between 45 and 85 years and over from 80% to 15% at 1 year from diagnosis;
- In age groups between 45 and 84 years from 45% to 11% at 3 years from diagnosis.
- In age groups between 45 and 79 years from 27% to 12% at 5 years from diagnosis.
Similar patterns of survival were apparent in both sexes when examining sex-specific relative survival by stage at diagnosis across age groups for males and females.
Relative survival by age (<50 years and ≥50 years age groups)
This section examines patterns in relative survival for people aged 50 years and over compared to people aged less than 50 years. A similar proportion of cases (between 10% and 13% of cancers) were not able to be staged for both age groups.
- People aged 50 years and over when diagnosed:
- Accounted for 93% of cases eligible for staging;
- Had a similar proportion of cases diagnosed at stage 1, 2 and 3 (with 22%, 25% and 23% of cases respectively) and a slightly lower proportion of stage 4 cancers (17%).
- People aged less than 50 years when diagnosed:
- Accounted for a low proportion of cases overall (7%), with the proportions of cancers generally increasing with increasing stage;
- Had around two in five cases (39%) diagnosed at an early stage (stage 1, 20%; stage 2, 19%) whilst more advanced cancers each accounted for 51% of cases (stage 3, 26%; stage 4, 25%).
For early stage and locally advanced colorectal cancers (stage 1-3), survival by stage at diagnosis was similar between these two groups at 1, 3 and 5 years from diagnosis.
For metastatic cancers (stage 4), those aged 50 years and over had a much lower survival than those aged less than 50 years:
- 47% compared to 72% at 1 year from diagnosis;
- 21% compared to 38% at 3 years from diagnosis;
- 13% compared to 22% at 5 years from diagnosis.
Observed survival by stage at diagnosis and remoteness area in 2011
For examination of survival by remoteness area, the data apply to observed rather than relative survival due to an absence of life tables. More information can be found in the ‘About the Data’ tab.
For colorectal cancers, observed survival by stage at diagnosis was generally similar across remoteness areas for early stage cancers (stage 1 and 2).
For locally advanced cancers (stage 3), there was a small but significant difference in observed survival between people living in Inner and Outer Regional areas compared to those living in Major Cities at 1 year (89% compared to 92%) and 3 years from diagnosis (70% compared to 75%).
For metastatic cancers (stage 4), there was a small but significant difference in observed survival in observed survival between people living in Inner and Outer Regional areas compared to those living in Major Cities at 3 years from diagnosis (17% compared to 23%). For stage 4 cancers, observed survival was not reported for Remote and Very Remote areas at 3 and 5 years from diagnosis due to small numbers.
Similar patterns were apparent in both sexes when examining 1, 3, and 5-year observed survival by stage at diagnosis for people living in different remoteness areas.
Observed survival by stage at diagnosis and socioeconomic status (SES) area in 2011
For examination of survival by SES areas, the data apply to observed rather than relative survival due to an absence of life tables. More information can be found in the ‘About the Data’ tab.
For colorectal cancers, observed survival by stage at diagnosis was generally similar across SES areas at 1, 3 and 5-years from diagnosis for people diagnosed with early stage or metastatic cancers (stage 1, 2 and 4).
For locally advanced cancers (stage 3), there was a small but significant difference in observed survival between people living in the:
- Highest SES areas (SES5, 95%) compared to lower SES areas (SES1-4, between 89% and 91%).
- Highest SES areas (SES5, 77%) compared to the lowest SES areas (SES1, 69%).
Similar patterns were apparent in both sexes, when examining 1, 3, and 5-year observed survival by stage at diagnosis for people living in different SES areas.
Observed survival by stage at diagnosis and Indigenous status in 2011
Analyses of survival by stage were not undertaken by Indigenous status due to small numbers.
About the data
The descriptive data in this report are used to describe patterns rather than test hypotheses. For this report, 95% confidence intervals (CIs) are used as a guide to report notable differences in survival. The following approach has been used for reporting these data:
- Unless otherwise stated, the patterns described in the text refer to differences where there is no overlap of 95% CIs and which are likely to be non-random differences.
- Differences where there is an overlap of 95% CIs are more likely to have occurred by chance. These differences are referred to in the text as ‘generally’ or ‘tended to’ occur. Differences with overlapping CIs should be interpreted with caution.
For analyses by age group, differences in survival between subsequent 5-year age groups (e.g. 45-49 years compared to 50-54 years) were not statistically significant but the overall trend showed a lower survival with increasing age. Data estimates were not provided for some age groups by stage due to small numbers.
Methodology:1
Relative survival is measure of survival for people diagnosed with cancer compared to survival for the general population. It is defined as a ratio of:
- Observed survival (numerator): The proportion of people who are alive following a specified amount of time (e.g. 1 year, 3 years or 5 years) after diagnosis of cancer (observed survival). Observed survival is calculated from population-based cancer data.
- Expected survival (denominator): The proportion of people in the general population who are alive over the same time interval (note: of equivalent age and sex to those with the cancer diagnosis). Expected survival is calculated from life tables for the entire Australian population.
For example, if 6 in 10 people with cancer are alive 5 years after their diagnosis (observed survival of 0.6) and 9 in 10 people of equivalent age and sex from the general population are alive after the same 5 years (expected survival of 0.9), then the relative survival of people with cancer would be 0.6 divided 0.9 which equates to 0.67. This means that individuals with cancer are 67% as likely to be alive for 5 years after their diagnosis compared with their counterparts in the general population.
Relative survival for colorectal cancer by RD-stage at diagnosis was calculated using the cohort method, using the period 2011–2016. In this method, a cohort of patients diagnosed with cancer is followed over time to estimate the proportion surviving for a selected timeframe (for example, 5 years), compared with the general population.3 As estimates of relative survival may vary, confidence intervals are calculated for these estimates to specify a range of values that are likely to contain the true relative survival for the population.
International comparisons of cancer survival should be interpreted with caution due to differences in cancer collection, coding and reporting practices, as well as differences in the methodologies used for calculating survival.1
Scope:
These data include cases with a principal diagnosis of colorectal cancer (C18.0, C18.2–C20) for which stage data were available. These data exclude:
- Cancers of the appendix (ICD-10 code C18.1).
- Cases identified from death certificates only.
- Certain morphology codes that were not eligible for staging, such as sarcomas, lymphomas or carcinoid tumours.
RD-stage
RD-stage at diagnosis is defined as the best estimate of summary TNM stage of diagnosis that can be derived by cancer registries from data sources available to them for invasive tumours. These data will be used for statistical purposes as opposed to clinical management. Clinical requirements for prognostic precision differ from epidemiological requirements for comparability and statistical completeness.4
Specifically, the collection of RD-stage is intended for epidemiological population-based analyses only – in particular, this information on stage at diagnosis will assist our understanding of the extent of cancer across tumour types and different sociodemographic groups, and associated cancer survival.
The Business Rules used to derive RD-stage have been tested and reviewed by all states and territories to ensure applicability across all Australian population-based cancer registries. The Business Rules have also been endorsed as a national standard for the collection of stage data by the AACR.
Australian Cancer Database5
Cancer incidence indicates the number of new cancers diagnosed during a specified time period (usually one year). The major source of national cancer incidence data is the ACD which contains records of all primary, malignant cancers (except basal cell and squamous cell carcinomas of the skin) diagnosed in Australia since 1982.
All Australian states and territories have legislation that makes cancer a notifiable disease. Various designated bodies, i.e., institutions such as hospitals, pathology laboratories and registries of births, deaths and marriages, are required to report cancer cases and deaths to their jurisdictional cancer registries.
Each registry supplies incidence data annually to the AIHW under an agreement between the registries and the AIHW. These data are compiled into the ACD, the only repository of national cancer incidence data.
National Death Index6
The National Death Index (NDI) is a database, housed at the AIHW, which contains records of all deaths occurring in Australia since 1980. The data are obtained from the Registrar of Births, Deaths and Marriages in each state and territory. The NDI is designed to facilitate the conduct of epidemiological studies and its use is strictly confined to medical research.
Linkage of RD-stage, the ACD and NDI
The data used for reporting this measure have been created by linkage of data from the RD-stage collection and the ACD. These data are therefore limited to records that have been matched across these two collections. For this analysis, 3.7% records in the RD-stage collection (approximately 2,500 out of 72,200 cases) have been excluded from these analyses for the following reasons:
- RD-stage record did not link to the ACD.
- The RD-stage record linked to an ACD record that was out of scope.
- RD-stage record was ineligible for staging (such as sarcomas, lymphomas or carcinoid tumours).
- RD-stage record was a duplicate.
A relatively small number of records (approximately 600, less than 1%) records in the ACD were in scope but did not link to the RD-stage collection. These records did not link because:
- They had been altered since being submitted to the ACD and were now out of scope; or
- Had been staged at a point after diagnosis but not at diagnosis.
Cancer incidence records from the linked ACD and RD-stage data were linked to the NDI to calculate the survival estimates in this report.
Data caveats:
- Data sourced from a linkage of the RD-stage, Australian Cancer Database and National Death Index data collections.
- Error bars indicate 95% confidence intervals.
- Survival greater than 100% applies where the survival of people with cancer exceeds the survival of people in the general population of equivalent age and sex over an equivalent time period.
- ‘All stages’ include cases where it was not possible to determine stage at diagnosis (‘unknown’ stage).
- This analysis presents relative survival estimates by RD-stage at diagnosis calculated using the cohort method for the period 2011–2016.
- Where the relevant life tables were not available (by remoteness area and socioeconomic status area of usual residence), survival estimates are presented for observed survival calculated using the cohort method for the period 2011–2016.
- Remoteness areas are classified according to the 2011 Australian Statistical Geography Standard (ASGS) Remoteness Areas. Not all remoteness areas are represented in all jurisdictions. Disaggregation by remoteness area is based on Statistical Area Level 2 (SA2) of usual residence at time of diagnosis.
- Socioeconomic groups are classified according to the SEIFA quintile using the Index of Relative Socioeconomic Disadvantage (IRSD). Disaggregation by SEIFA quintile is based on 2011 classifications of Statistical Areas Level 2 (SA2) of usual residence at time of diagnosis.
- Analyses by Indigenous status have not been presented due to small numbers.
References
Activity in this area
Cancer Australia, 2008. A National Cancer Data Strategy for Australia. (https://canceraustralia.gov.au/sites/default/files/publications/ncds_final_web1_504af02093a68.pdf).
Cancer Australia. The Stage, Treatment, and Recurrence project. (https://canceraustralia.gov.au/research-data/cancer-data/improving-cancer-data).
Data
Australian Institute of Health and Welfare.
Australian Cancer Incidence and Mortality (ACIM) books provide incidence and mortality by cancer type and selected demographic groups. (https://www.aihw.gov.au/reports/cancer/acim-books/contents/acim-books).
Australian Institute of Health and Welfare.
‘Cancer Data in Australia’ consolidates the ACIM books, Cancer Compendium and summary tables from Cancer in Australia into one product. This was published in December 2018. (https://www.aihw.gov.au/reports/cancer/cancer-data-in-australia/contents/summary)
National Cancer Intelligence Network.
The National Cancer Registration and Analysis Service provides information on cancer 1-year relative survival by stage at diagnosis in England.
(http://www.ncin.org.uk/publications/survival_by_stage).
References
1. Australian Institute of Health and Welfare. 2017. Cancer in Australia 2017. Canberra: AIHW.
2. American Joint Committee on Cancer. 2018. Cancer Staging System: AJCC; [cited 2018]. Available from: https://cancerstaging.org/references-tools/Pages/What-is-Cancer-Staging.aspx.
3. Australian Institute of Health and Welfare. 2018. Cancer Data in Australia. Canberra: AIHW. Available from: https://www.aihw.gov.au/reports/cancer/cancer-data-in-australia/contents/summary.
4. Walters S., Maringe C., Butler J., Brierley J. D., Rachet B., Coleman M. P. 2013. Comparability of stage data in cancer registries in six countries: lessons from the International Cancer Benchmarking Partnership. Int J Cancer. 132(3):676-85.
5. Australian Institute of Health and Welfare. 2014. Australian Cancer Database, 2014; Quality Statement Canberra: AIHW [cited 2018]. Available from: http://meteor.aihw.gov.au/content/index.phtml/itemId/687104.
6. Australian Institute of Health and Welfare. 2012. National Death Index; Quality Statement Canberra: AIHW [cited 2018]. Available from: http://meteor.aihw.gov.au/content/index.phtml/itemId/480010.