Diagnosis
The diagnosis data available were not considered complete enough to allow formal reporting for the following performance indicators:
- PI 5a – Adenoma detection rate
- PI 5b – Positive predictive value of diagnostic assessment for detecting adenoma
- PI 8 – Cancer clinico-pathological stage distribution
The following performance indicators are reported, but have not had results updated in this report from those included in the previous monitoring report:
- PI 6a – Bowel cancer detection rate
- PI 6b – Positive predictive value (PPV) of diagnostic assessment for detecting bowel cancer
- PI 7 – Interval cancer rate
These will be updated in future monitoring reports.
See Analysis of bowel cancer outcomes for the National Bowel Cancer Screening Program 2018 (AIHW 2018) for the most recent stage distribution data.
See Bowel abnormality detection using available assessment and histopathology data at the end of this section for a summary of bowel abnormality detection using data available.
PI 6a – Bowel cancer detection rate
PI 6a definition
The proportion of people who screened through the NBCSP between 1 January 2019 and 31 December 2019 and were diagnosed with a screen-detected bowel (colorectal) cancer within that period or by 31 December 2020.
Rationale: The cancer detection rate is a key indicator of program effectiveness, especially when comparing this rate to the known bowel cancer incidence rate in the target population. Monitoring the cancer detection rate by various stratifications may also reveal emerging positive or negative trends that need to be investigated and rectified if necessary.
Data quality: All iFOBT kits returned are recorded in the NCSR. These are matched with national cancer incidence data, which is considered complete due to cancer being a notifiable disease.
Guide to interpretation: Results for this indicator have not been updated in this report and match those reported in the previous monitoring report.
The matching process across data sets involved creating record pairs by matching records from the NCSR with records from the Australian Cancer Database. Due to the nature of probabilistic linkage, there may be some minor but unavoidable inaccuracy in the linkage process, and this should be considered when interpreting the results.
This indicator counts all valid iFOBT tests analysed in the defined period, not tests analysed from those invited in the defined period.
The rollout of biennial screening was completed in 2019, with years before that having a smaller set of target invitation ages (Table 1.2). As the detection rate differs by age at screen, results across earlier program years may vary due to differences in participant age distribution. Future data, from 2019 onwards, should be less affected.
Detection rate data by Indigenous Australians, by preferred language spoken at home, and by disability status are not currently available.
National bowel cancer detection rate, 2019: 20.3 cancers diagnosed per 10,000 people who returned a valid screening test.
The following apply to the 1,321,993 people who returned a valid iFOBT kit from 1 January 2019 to 31 December 2019:
Australia-wide: A total of 2,683 screen-detected bowel cancers were diagnosed in people who participated in the NBCSP, giving an overall Australia-wide bowel cancer detection rate of 20.3 cancers diagnosed per 10,000 people screened (Table A3.23).
Sex: Males had a higher cancer detection rate than females (24.6 cancers per 10,000 screened compared with 16.5 per 10,000 screened (Table A3.23).
Age: The cancer detection rate increased with each age group, from 11.6 cancers per 10,000 screened for people aged 50–54 at screening to 29.5 per 10,000 for people aged 70–74 (Figure 3.18a).
Screening round: The cancer detection rate was highest for people returning their first screening test (28.8 cancers per 10,000 screened) (Figure 3.18b). This varied by age at first screen, from 14.1 per 10,000 screened for people aged 50–54 to 61.1 per 10,000 screened for people aged 70–74 (Table A3.24b).
Regarding rescreeners:
- those rescreening at their next biennial invitation had a cancer detection rate of 15.5 cancers detected per 10,000 screened, and
- those whose previous screening test was more than 2.5 years ago had a cancer detection rate of 18.6 cancers detected per 10,000 screened.
Figure 3.18a: Bowel cancer detection rate of people aged 50–74, by sex and age, Australia, 2019
This figure comprises a vertical bar chart showing the colorectal cancer detection rate for males and females by age group. The chart shows that the colorectal cancer detection rate was higher for males than females and increased with each age group. The lowest colorectal cancer detection rate was for females aged 50–54 (10.3 per 10,000) and the highest for males aged 70–74 (35.8 per 10,000).
| Age group (years) | Males | Females |
|---|---|---|
| 50-54 | 13.1 | 10.3 |
| 55-59 | 15.9 | 12.3 |
| 60-64 | 23 | 15.4 |
| 65-69 | 35 | 21.1 |
| 70-74 | 35.8 | 23.6 |
Source: Table A3.23.
Figure 3.18b: Bowel cancer detection rate of people aged 50–74, by screening round, Australia, 2019
This figure comprises a vertical bar chart showing the colorectal cancer detection rate by screening round. The chart shows that the colorectal cancer detection rate was highest for people receiving their first round of screening (28.8 per 10,000 compared with 18.6 per 10,000 for those completing a subsequent screening round after more than 2 years).
| Screening Round | Cancer detection rate (per 10,000) |
|---|---|
| First | 28.8 |
| Subsequent (≤2 years) | 15.5 |
| Subsequent (>2 years) | 18.6 |
Source: Table A3.24a.
Trend: Since 2010, the cancer detection rate has fluctuated between 19 and 27 cancers diagnosed per 10,000 screened. For 2007 and 2008, the target ages invited were mainly 55- and 65-year-olds, leading to higher rates. For 2009, there was a change in the kit that meant only strongly positive screens were likely to be detected as positive; negative results were sent a replacement kit (Figure 3.19).
Figure 3.19: Bowel cancer detection rate of people aged 50–75+, by sex, Australia, 2007 to 2019
This line chart depicts the colorectal cancer detection rate for the period 2007 to 2019 for males, females and persons. It shows that the overall colorectal cancer detection rate increased in 2009, before decreasing between 2010 and 2015. The rate dropped to 20.3 per 10,000 people in 2019.
| Years | Males | Females | Persons |
|---|---|---|---|
| 2007 | 42.2 | 23.9 | 32.4 |
| 2008 | 34.7 | 18.9 | 26.2 |
| 2009 | 50.6 | 30.2 | 39.7 |
| 2010 | 29.5 | 17.4 | 23.1 |
| 2011 | 29.4 | 16.8 | 22.7 |
| 2012 | 29.5 | 18.7 | 23.8 |
| 2013 | 26.6 | 16.3 | 21.1 |
| 2014 | 26.4 | 13.3 | 19.4 |
| 2015 | 30.3 | 18.1 | 23.9 |
| 2016 | 32.1 | 21.9 | 26.8 |
| 2017 | 27.7 | 17.4 | 22.3 |
| 2018 | 26.7 | 17.3 | 21.7 |
| 2019 | 24.6 | 16.5 | 20.3 |
Trend data used the performance indicator specifications retrospectively on previous years’ data.
Source: Table A3.26.
State or territory: The cancer detection rate was highest for people living in the Northern Territory (30.7 cancers detected per 10,000 screened) and lowest for people living in the Australian Capital Territory (14.1 cancers detected per 10,000 screened) (Figure 3.20).
Figure 3.20: Bowel cancer detection rate of people aged 50–75+, by state or territory, Australia, 2019
This vertical bar chart shows that the colorectal cancer detection rate was highest for people living in the Northern Territory with 30.7 per 10,000 people and lowest for people living in the Australian Capital Territory with 19.3 per 10,000 people.
| State or territory | Cancer detection rate (per 10,000) |
|---|---|
| NSW | 20.8 |
| Vic | 19.3 |
| Qld | 22.4 |
| WA | 17.1 |
| SA | 22.2 |
| Tas | 17.8 |
| ACT | 14.1 |
| NT | 30.7 |
Source: Table A3.25.
PI 6b – Positive predictive value (PPV) of diagnostic assessment for detecting bowel cancer
PI6b definition
The percentage of people who returned a positive screening test and underwent diagnostic assessment between 1 January 2019 and 31 December 2019 and were diagnosed with a screen-detected bowel (colorectal) cancer within that period or by 31 December 2020.
Rationale: This indicator calculates the positive predictive value (PPV) of diagnostic assessment for detecting cancers; it is a measure of the quality and effectiveness of diagnostic assessment. Monitoring the PPV by various stratifications may also reveal emerging positive or negative trends that need to be investigated and rectified if necessary.
Data quality: All positive iFOBT results are recorded in the NCSR; however, not all diagnostic assessments are. This may lead to PPV results that are slightly higher than in reality. These are matched with national cancer incidence data, which is considered complete due to cancer being a notifiable disease.
Guide to interpretation: Results for this indicator have not been updated in this report and match those reported in the previous monitoring report.
The matching process across data sets involved creating record pairs by matching records from the NCSR with records from the Australian Cancer Database. Due to the nature of probabilistic linkage, there may be some minor but unavoidable inaccuracy in the linkage process, and this should be considered when interpreting the results.
This indicator counts all diagnostic assessments in the defined period, not tests analysed from those invited in the defined period; therefore, the cohort for this indicator is different from that in indicator 6a. Further, the denominator is therefore affected by accuracy of diagnostic assessment notifications to the register, which are not mandated by the NBCSP. This should be taken into consideration when analysing this indicator.
The rollout of biennial screening was completed in 2019, with years before that having a smaller set of target invitation ages (Table 1.2). As the PPV differs by age at screen, results across earlier program years may vary due to differences in participant age distribution. Future data, from 2019 onwards, should be less affected.
PPV data by Indigenous Australians, by preferred language spoken at home, and by disability status are not currently available.
National positive predictive value (PPV) of diagnostic assessment for detecting bowel cancer, 2019: 3.8 cancers per 100 diagnostic assessments after a positive screen.
The following apply to the 64,510 people who underwent a diagnostic assessment after a positive screen from 1 January 2019 to 31 December 2019:
Australia-wide: A total of 2,463 screen-detected bowel cancers were diagnosed in people who underwent a diagnostic assessment after a positive screen, giving an overall Australia-wide positive predictive value (PPV) of 3.8% (Table A3.27).
Sex: Males had a higher PPV than females (4.1% compared with 3.4% (Table A3.27)).
Age: The PPV increased with each age group, from 2.4% for people aged 50–54 to 4.8% for people aged 70–74 (Figure 3.21a).
Screening round: The PPV was highest for people with a positive screen result from their first screening test (5.0%) (Figure 3.21b). This varied by age at first screen, from 2.7% for people aged 50–54 to 7.8% for people aged 70–74 (Table A3.28b).
For those with a positive screen result in a subsequent screening round:
- those rescreening at their next biennial invitation had a PPV of 2.8%, and
- those whose previous screening test was more than 2.5 years ago had a PPV of 3.6%.
Figure 3.21a: PPV of diagnostic assessment for detecting bowel cancer for people aged 50–74, by sex and age, Australia, 2019
The chart depicts the PPV of diagnostic assessment for detecting colorectal cancer rate for males and females by age group. It shows that the PPV of diagnostic assessment rate increased in each age group and was higher for males than females in each age group.
| Age group (years) | Males | Females |
|---|---|---|
| 50-54 | 2.4% | 2.3% |
| 55-59 | 2.8% | 3% |
| 60-64 | 4% | 3.1% |
| 65-69 | 5.2% | 4.1% |
| 70-74 | 5.1% | 4.3% |
Source: Table A3.27
Figure 3.21b: PPV of diagnostic assessment for detecting bowel cancer for people aged 50–74, by screening round, Australia, 2019
The chart depicts the PPV of diagnostic assessment for detecting colorectal cancer rate by screening round. The chart shows that the PPV of diagnostic assessment rate was higher for people receiving their first screening (5.0% in the first invitation rounds compared with 3.6% for subsequent screening rounds after more than 2 years).
| Screening Round | PPV of diagnostic assessment |
|---|---|
| First | 5% |
| Subsequent (≤2 years) | 2.8% |
| Subsequent (>2 years) | 3.6% |
Source: Table A3.28a.
Trend: Since 2010, the PPV has fluctuated between 3.7% and 5.2%. (Figure 3.22). The rollout of biennial screening was completed in 2019, with years before that having a smaller set of target invitation ages (Table 1.2). As the PPV differs by age at screen, results across earlier program years may vary due to differences in participant age distribution. Future data, from 2019 onwards, should be less affected.
As noted under Guide to interpretation, the PPV is affected by the completeness of diagnostic assessment notifications to the NCSR, which are not mandated by the NBCSP.
Figure 3.22: PPV of diagnostic assessment for detecting bowel cancer for people aged 50–74, by sex, Australia, 2007 to 2019
This line chart shows the PPV of diagnostic assessment for detecting colorectal cancer rate for the period 2007 to 2019 for males, females and persons. It illustrates that the overall PPV of diagnostic assessment decreased significantly in 2010 and 2014, before increasing in 2016 and then dropping to 3.8% in 2019.
| Years | Males | Females | Persons |
|---|---|---|---|
| 2007 | 6% | 4.4% | 5.3% |
| 2008 | 6.3% | 4.8% | 5.6% |
| 2009 | 6.2% | 4.2% | 5.3% |
| 2010 | 4.2% | 3.2% | 3.7% |
| 2011 | 5.1% | 3.8% | 4.5% |
| 2012 | 5.4% | 3.9% | 4.6% |
| 2013 | 5% | 3.6% | 4.3% |
| 2014 | 5% | 3.2% | 4.1% |
| 2015 | 5.2% | 3.6% | 4.4% |
| 2016 | 5.9% | 4.5% | 5.2% |
| 2017 | 5.4% | 3.9% | 4.7% |
| 2018 | 4.9% | 3.7% | 4.3% |
| 2019 | 4.1% | 3.4% | 3.8% |
Trend data used the performance indicator specifications retrospectively on previous years’ data.
Source: Table A3.30.
State or territory: The PPV was highest for people living in the Northern Territory (6.8%) and lowest for people living in Tasmania (2.8%) (Figure 3.23).
Figure 3.23: PPV of diagnostic assessment for detecting bowel cancer for people aged 50–74, by state or territory, Australia, 2019
This vertical bar chart shows that the PPV of diagnostic assessment for detecting colorectal cancer rate was highest for people living in the Northern Territory with 6.8% and lowest for people living in Tasmania with 2.8%.
| State or territory | PPV of diagnostic assessment |
|---|---|
| NSW | 4.4% |
| Vic | 3.8% |
| Qld | 3.6% |
| WA | 3.2% |
| SA | 3.7% |
| Tas | 2.8% |
| ACT | 3.1% |
| NT | 6.8% |
Source: Table A3.29.
PI 7 – Interval cancer rate
PI 7 definition
The proportion of people who returned a negative or inconclusive screening test between 1 January 2018 and 31 December 2018 and were diagnosed with bowel (colorectal) cancer within 24 months of their screening test.
Rationale: A low interval cancer rate in a population-based screening program is desirable. However, interval cancers are inevitable. A high interval cancer rate reduces the potential for the program to achieve reductions in morbidity and mortality from bowel cancer. Monitoring interval cancer rates is also important to assess the diagnostic assessment component of the screening pathway.
Monitoring the interval cancer rate by various stratifications may also reveal emerging positive or negative trends that need to be investigated and rectified if necessary.
Data quality: All iFOBT results are recorded in the NCSR. These are matched with national cancer incidence data, which is considered complete due to cancer being a notifiable disease.
Guide to interpretation: Results for this indicator have not been updated in this report and match those reported in the previous monitoring report.
The matching process across data sets involved creating record pairs by matching records from the NCSR with records from the Australian Cancer Database. Due to the nature of probabilistic linkage, there may be some minor but unavoidable inaccuracy in the linkage process, and this should be considered when interpreting the results.
This indicator includes all iFOBT tests analysed as negative in the defined period, not negative tests from those invited in the defined period.
The rollout of biennial screening was completed in 2019, with years before that having a smaller set of target invitation ages (Table 1.2). As the interval cancer rate differs by age at screen, results across earlier program years may vary due to differences in participant age distribution. Future data, from 2019 onwards, should be less affected.
Interval cancer rate data by Indigenous Australians, by preferred language spoken at home, and by disability status are not currently available.
National interval cancer rate, 2018: 6.3 cancers diagnosed per 10,000 people who returned a negative or inconclusive screening test.
The following apply to the 1,118,192 people who returned an iFOBT kit from 1 January 2018 to 31 December 2018 that was negative or inconclusive:
Australia-wide: A total of 701 interval cancers were diagnosed, giving an overall Australia-wide interval cancer rate of 6.3 cancers diagnosed within 2 years per 10,000 people with a negative or inconclusive iFOBT (Table A3.31).
Sex: Males had a higher interval cancer rate than females (6.7 per 10,000 negative/inconclusive iFOBTs compared with 5.9 per 10,000 negative/inconclusive iFOBTs) (Table A3.31).
Age: The interval cancer rate generally increased with increasing age groups, from 3.2 per 10,000 negative/inconclusive iFOBTs for people aged 50–54 to 10.5 per 10,000 for people aged 70–74 (Figure 3.24a).
Screening round: The interval cancer rate for those returning their first iFOBT was 5.8 cancers detected per 10,000 negative/inconclusive iFOBTs (Figure 3.24b).
For those diagnosed with an interval cancer after a subsequent screening round:
- the interval cancer rate was highest for people rescreening at a biennial screening interval (8.0 per 10,000 negative/inconclusive iFOBTs). This was mainly due to the biennial screening rollout (by 2018, Table 1.2) only having invitees older than 60 (who have higher rates of interval cancers than those aged 50–59) being eligible for a rescreening invitation within 2 years of their previous iFOBT (Table A3.32b).
- those whose previous screening test was more than 2.5 years ago, had an interval cancer rate of 5.7 interval cancers detected per 10,000 negative/inconclusive iFOBT.
Figure 3.24a: Interval cancer rate of people aged 50–74, by sex and age, Australia, 2018
The chart illustrates the interval cancer rate for males and females by age group. It shows that the interval cancer rate increased in each age group and was higher for males than females in each age group, especially for males aged 70–74.
| Age group (years) | Males | Females |
|---|---|---|
| 50-54 | 3.1 | 3.3 |
| 55-59 | 3.7 | 3 |
| 60-64 | 5.7 | 5.6 |
| 65-69 | 6.6 | 6.6 |
| 70-74 | 12 | 9.2 |
Source: Table A3.31.
Figure 3.24b: Interval cancer rate of people aged 50–74, by screening round, Australia, 2018
This figure presents a vertical bar chart showing the interval cancer rate by screening round. The chart indicates that the interval cancer rate was highest for people receiving their subsequent screening round within 2 years after their first round (8 per 10,000 per), compared with those screening for the first time (5.8 per 10,000) and those receiving a subsequent screening round after more than 2 years (5.7 per 10,000).
| Screening Round | Interval cancer rate (per 10,000) |
|---|---|
| First | 5.8 |
| Subsequent (≤2 years) | 8 |
| Subsequent (>2 years) | 5.7 |
Source: Table A3.32a.
Trend: The interval cancer rate has increased between 2010 and 2018 from 3.5 to 6.3 interval cancers detected per 10,000 negative/inconclusive iFOBTs (Figure 3.25). The rollout of biennial screening was completed in 2019, with years before that having a smaller set of target invitation ages (Table 1.2). As the interval cancer rate differs by age at screen, results across earlier program years may vary due to differences in participant age distribution. For example, reporting on interval cancers in those aged 70–74 (the age group with the highest rates of interval cancers (Figure 3.24)) has only been possible since 2015 due to the biennial rollout. Future data, from 2019 onwards, should be less affected.
Figure 3.25: Interval cancer rate of people aged 50–74, by sex, Australia, 2007 to 2018
This line chart shows the interval cancer rate 2007 to 2018 for males, females and persons. It indicates that the overall interval cancer rate decreased significantly in 2010 and 2014, before increasing to 6.3 per 10,000 in 2018.
| Years | Males | Females | Persons |
|---|---|---|---|
| 2007 | 6.6 | 5.2 | 5.8 |
| 2008 | 5.4 | 3.9 | 4.6 |
| 2009 | 5 | 4.7 | 4.9 |
| 2010 | 4.1 | 3 | 3.5 |
| 2011 | 4.3 | 3.3 | 3.7 |
| 2012 | 4.8 | 3.7 | 4.2 |
| 2013 | 4.2 | 4.2 | 4.2 |
| 2014 | 4.9 | 2.9 | 3.8 |
| 2015 | 4.5 | 4.2 | 4.3 |
| 2016 | 5.9 | 5.9 | 5.9 |
| 2017 | 5.8 | 4.3 | 5 |
| 2018 | 6.7 | 5.9 | 6.3 |
Trend data used the performance indicator specifications retrospectively on previous years’ data.
Source: Table A3.34.
State or territory: The interval cancer rate was highest for people living in Western Australia (6.8 per 10,000 negative/inconclusive iFOBTs) and lowest for people living in the Australian Capital Territory (5.5 per 10,000 negative/inconclusive iFOBTs) (Figure 3.26). Interval cancer rates for the Northern Territory and Tasmania have been suppressed in Figure 3.26 due to low counts.
Figure 3.26: Interval cancer rate of people aged 50–74, by state or territory, Australia, 2018
This vertical bar chart shows that the interval cancer rate was highest for people living in the Western Australia with 6.8 per 10,000 and lowest for people living in the Australian Capital Territory with 5.5 per 10,000. Other state or territories ranged between 5.8–6.7 per 10,000.
| State or territory | Interval cancer rate (per 10,000) |
|---|---|
| NSW | 6.5 |
| Vic | 5.8 |
| Qld | 6.6 |
| WA | 6.8 |
| SA | 6.7 |
| Tas | n.p. |
| ACT | 5.5 |
| NT | n.p. |
Source: Table A3.33.
Bowel abnormality detection results for 2024
Diagnosis data for 2024 were not considered complete enough to allow for all formal performance indicator reporting of NBCSP diagnostic outcomes in Performance of the screening program, hence those indicators use the latest available, though earlier, reporting periods with more complete data. As an alternative, a summary of bowel abnormality detection results for those assessed in 2024 are presented here for information, using available outcome data from colonoscopy and histopathology forms. In this report colonoscopy form data and MBS claims have been supplemented with Participant follow-up function (PFUF) data for those who had a positive screening test, increasing the number of known colonoscopies. However, colonoscopies sourced from PFUF reports or MBS claims have no accompanying outcome data so are excluded here.
Bowel abnormality detection using available assessment and histopathology data
Of the 62,981 participants who had a diagnostic assessment in 2024, 19,244 had outcome data. Of these:
- 195 (1.0%) had a bowel cancer detected and confirmed by histopathology
- 470 (2.4%) had a suspected bowel cancer at assessment that was still awaiting histopathological diagnosis
- 5,911 (30.7%) had an adenoma diagnosed by histopathology
- 7,018 (36.5%) had no adenoma or cancer recorded (includes those with no issue noted, or other diagnoses)
- 5,650 (29.4%) were still awaiting histopathology outcomes for a polyp biopsy sample (not suspected of being bowel cancer) to be reported to the NCSR (Table A3.35).
Rates of bowel cancer and adenoma detection differed by state or territory (Table A3.36). However, differences across states and territories may be affected by differences in return rates of histopathology forms and should be interpreted with caution.
Performance indicators 6a, 6b and 7 in ‘Performance of the screening program, Diagnosis’ use notifiable cancer incidence data for 2007–2020, and performance indicator 6b shows that 3.8% of those with a positive screen and diagnostic assessment in 2019 were diagnosed with bowel cancer. Therefore, due to incomplete colonoscopy and histopathology form return, the 1.0% diagnosed with bowel cancer in 2024 is likely underreported. However, including the 2.4% suspected of having bowel cancer in 2024 improves likely cancer detection accuracy.
AIHW (2018) Analysis of bowel cancer outcomes for the National Bowel Cancer Screening Program 2018, AIHW, Australian Government, accessed 09 May 2022.