The introduction of the National Bowel Cancer Screening Program (NBCSP) has resulted in a clinically significant shift to earlier CRC stage evident after five years from the program’s implementation.

A retrospective data-linkage study evaluated 2.6 million colonoscopies performed in NSW over three time periods from before the NBCSP (Period A, 1998-2006), immediately after NBCSP (Period B, 2007-2011) and subsequent years (Period C, 2012-2017).

The study, published in the ANZ Journal of Surgery [link here], found the annual colonoscopy rate per 100,000 population, annual polypectomy rate per 100,000 as well as colonoscopy to polypectomy ratio all significantly increased over the three time periods.

Meanwhile, the overall incidence of CRC per 100,000 population remained stable over the first two periods but was significantly lower in the later period (P< 0.001).

“Periods A and B had similar percentage of patients diagnosed with early CRC (stages I and II), however Period C had a significant 7% increase,” the study said.

“Stage I and IIa patient ratios (those definitely not requiring adjuvant chemotherapy) significantly increased from 0.44 to 0.45 to 0.55 in Periods A, B and C respectively (P=0.003).”

The study also found mean tumour sizes were significantly smaller in Period C compared to earlier time periods (P< 0.001).

“Period C also had a lower number of positive lymph nodes (P = 0.001), and less frequent positive apical lymph nodes (P = 0.004).”

In other findings:

• significantly more tumours in Period C were poorly differentiated (P = 0.004).
• the proportion of right sided tumours increased over time (P = 0.026)
• microsatellite instability/MMR deficiency (P = 0.001) and BRAF mutation (P = 0.001) increased.

“Earlier detection of right sided, smaller cancers with genetic mutations via increasing screening colonoscopies would therefore be expected to contribute to remarkable prognostic improvement in the long-term,” the study said.

The investigators, from the Royal North Shore Hospital and University of Sydney, said the stage shift in CRC had two potential benefits – reducing mortality via earlier detection and reducing the requirement for adjuvant chemotherapy after potentially curative resections.

“Currently 29%–60% of high-risk stage II patients receive adjuvant chemotherapy. Some have argued that this may be over-treatment and it is specifically in younger patients where a convincing shift to Stages I and IIa (definitely not requiring adjuvant chemotherapy) as shown in our study would confer long-term benefits.”

“The shift to earlier CRC stages established in our study resulted in fewer patients potentially needing adjuvant chemotherapy, which is a major, and underreported, benefit achievable through increased uptake of colonoscopy and CRC screening programs.”

The study, led by colorectal surgeon Dr Mina Sarofim, noted that the risks associated with colonoscopy such as major bleeding or perforation were rare. However, there was also the potential for some psychological distress associated with participation in a bowel cancer screening program.

Senior investigators on the study included oncologist Professor Nick Pavlakis, gastroenterologist Associate Professor Ian Norton and surgeon Professor Alexander Engel.

Continued good colonoscopy

Gastroenterological Society of Australia (GESA) President Professor Alex Boussioutas told the limbic that, notwithstanding the limitations of a retrospective study based on administrative data, the study findings were a good news story.

“Even in small papers like this, there’s a positive message to give to patients that if you do this [screening], then sure, you might get a cancer identified but you could get a cancer at stage 1 where we can resect it.”

“The future of this is noninvasive surgery as well. We are now able to do a lot more endoscopically and we might get to the stage of very early cancer … where we can potentially resect that using endoscopic means and not surgery.”

He said the findings were a positive signal of the benefits of the NBCSP.

“The benefits will come from continued good colonoscopy and good polypectomy – making sure we remove the polyps before they get a chance to become cancer.”

He said a cost analysis would likely confirm that saving people from chemotherapy, major surgery and consequences such as time off work was a huge benefit compared to the screening costs of a program based on an inexpensive FOBT followed by colonoscopy.

Meanwhile, Bowel Cancer Australia has called for the Federal Minister for Health and Aged Care to fund and implement the 2023 recommendation [link here] to lower the entry age to the NBCSP from 50 to 45 years.

Mr Julien Wiggins, CEO of Bowel Cancer Australia, said 56% of all early-onset CRC cases and 64% of all early-onset CRC deaths occur in people aged 40-49.

“We need to be bold as we should be able to increase screening participation at the same time as offering screening to people aged 45-74. The most important screening test is the one that gets done,” he said.

Participation in the NBCSP currently sits at about 40% for the current target population of 50-74 year olds.

Professor Karen Canfell, Chair of Cancer Council’s National Cancer Screening and Immunisation Committee, said it was important to continue to support more eligible Australians to do the initial screening test.

“Our published research shows that investing in communication strategies such as mass media campaigns to increase bowel cancer screening participation is one of the strongest public health investments available to governments. Recent national and state campaigns are estimated to have saved a year of life for every $3,800 invested – which is extremely cost-effective in health economic terms,” she said.

She told the limbic preliminary data shows around 89,500 extra people completed their screening test during the 2022 campaign period.

“While we don’t have precise figures, given the high prevalence of bowel cancer and of adenomas…it’s likely that hundreds of people among those additional screening participants had an asymptomatic precancerous polyp or an early-stage bowel cancer treated because they completed the test.”