Why is this important? Interval cancers are cancers that are diagnosed after a negative screening test, but before a participant is due to come back for their next screen. Monitoring of interval cancers provides a mechanism to evaluate the impact of screening programs on colorectal cancer mortality in the target populations and is an important measure of the effectiveness of screening and diagnostic follow-up.1 In this report, we measure interval cancers that develop at two time points:
- After a negative fecal test result
- After a negative colonoscopy as a follow-up to a positive fecal result
1. Interval cancer rate after negative fecal test result
Indicator definition: The number of individuals (per 1000 with a negative fecal test screening result) who were subsequently diagnosed with colorectal cancer before their next scheduled screening test
Numerator: The number of people subsequently diagnosed with colorectal cancer within 2 years of a negative fecal test result in the measurement timeframe
Denominator: The number of individuals with negative fecal test screening result within the measurement timeframe.
How does 2014/15 compare to 2011/12? Compared with data in the colorectal cancer screening report for 2013-14 where 0.3 – 1.9 interval cancers were found per 1,000 screens, two jurisdictions have had an increase in interval cancers, and two have seen a decrease in 2014/15.
Rate (per 1,000) of interval colorectal cancers within 24 months of fecal tests with normal result among individuals aged 50-74, by jurisdiction, fecal tests from 2014 – 2015
Text description and footnotes
Interval cancers after a normal fecal test range from 0.7 per 1,000 screens in Saskatchewan to 3.2 per 1,000 people screened in Prince Edward Island.
2. Post-colonoscopy colorectal cancer rate after negative colonoscopy performed for positive fecal test
Indicator definition: The number of people per 1000 who received a follow-up colonoscopy who were diagnosed with colorectal cancer between 6 month and 3 years after a normal colonoscopy following a positive fecal test.
Numerator: The number of people who were subsequently diagnosed with colorectal cancer within 6 – 36 months of their normal colonoscopy.
Denominator: The number of people with an abnormal fecal test screening result within the measurement timeframe and colonoscopy results negative for colorectal cancer (performed within 6 months of the abnormal fecal test).
Rate (per 1,000) of post-colonoscopy colorectal cancers within 6-36 months since normal colonoscopy, among individuals aged 50-74, Saskatchewan and Prince Edward Island combined, fecal tests from 2012 – 2013
*Fecal tests from 2012-2013, individuals aged 50-74, Saskatchewan and Prince Edward Island combined
Text description and footnotes
Saskatchewan and Prince Edward Island provided data for this indicator. However, due to small numbers data from Prince Edward Island cannot be reported on its own.
In Saskatchewan and Prince Edward Island combined, there are 3.0 post-colonoscopy colorectal cancers per 1,000 normal colonoscopies.
1 – Garcia M, Domènech X, Vidal C, Torné E, Milà E, Binefa G, et al. Interval cancers in a population-based screening program for colorectal cancer in Catalonia, Spain. Gastroenterol Res Pract. 2015;2015:672410. doi: 10.1155/2015/672410.