CT colonography could be the solution to endoscopy waiting list blowouts

Australian clinicians are pushing computer tomography colonography (CTC) as a potential solution to increasing endoscopy demand, suggesting the method is safe, accurate and underused.

It comes despite concerns the procedure has little sensitivity to small, flat polyps; lacks therapeutic capacity; potentially exposes patients to multiple procedures; and, in an ideal world where endoscopists had appropriate funding and infrastructure, mostly unnecessary.

Published in Internal Medicine Journal, a brief communication by Adelaide gastroenterologists, radiologists and researchers argues CTC is useful and could reduce wait times to, and increase uptake of, colorectal cancer (CRC) screening in select populations.

It cited a meta-analysis reporting sensitivities of 85% and 91% for polyps above 6 mm and 10 mm, respectively and a Netherlands-based study showing patients aged 50–75 were more likely to undergo non-cathartic CTC than optical colonoscopy (OC) (RR:  1.56, P < 0.0001). The diagnostic yield of advanced neoplasia based on participation rate per 100 invitees were similar between the two methods (RR: 0.74, P = 0.07), it read.

“Thus, CTC could be considered as an alternative to OC for population screening of CRC, particularly where participation rates are low or access to OC is limited by prohibitive waiting times,” the authors from the University of Adelaide, Queen Elizabeth Hospital and Basil Hetzel Institute for Translational Health Research, Adelaide, wrote.

In Australia, the procedure is indicated for “asymptomatic and symptomatic patients at higher risk for an invasive procedure, incomplete colonoscopy and evaluation of synchronous CRC in patients with obstructing tumours preventing passage of the colonoscope”. However, it’s not recommended for patients with active inflammatory bowel disease or diverticulitis, “due to the conceptual risk of bowel perforation”, the communication read.

Despite the broad indication, CTC has relatively low rates of utilisation, while OC remains the mainstay investigation in CRC screening.

In 2020, nearly 850,000 colonoscopies were conducted in Australia, versus 5,669 CTCs, the article noted.

Heavy-reliance on one technique, along with the National Bowel Cancer Screening Program rollout, means colonoscopy demand has outstripped the capacity of endoscopic services and led to long wait times, “potentially depriving patients of an opportunity for early cancer detection”, the authors wrote.

While a retrospective review of a Western Australian hospital showed patients who needed colonoscopy within 30 days had colonoscopies on time, those who needed assessing within 90 or 365 days had to wait an extra 113 and 238 days, respectively.

Further, a 2021 study found time to OC from faecal occult blood test was 45 and 69 days in the private and public healthcare systems, respectively — a delay of 15 and 39 days.

“With an ever-growing demand for endoscopic services, increased utilisation of CTC could reduce waiting times for colonoscopy, thereby broadening access to timely and effective CRC screening,” the authors wrote.

Value in practice

They noted the procedure could be done with faecal tagging without catharsis, which may make it more tolerable for patients than CTC or OC with catharsis and support increased uptake.

However, concerns about ionising radiation, lacking capacity for therapeutic intervention and “potentially diminished sensitivity for flat serrated polyps” have so far hampered CTC’s uptake.

The inability to remove polyps on CTC means lesion-positive patients would have to undergo two procedures, and likely, two rounds of catharsis.

As a result, past president of the Colorectal Surgical Society of Australia and New Zealand Mr James Keck previously told the limbic CTC would be “a good screening test” if polyp risk was low, “but if we know already that at least half the patients having a referral have a polyp, then at least half [will end up having the two procedures]”. And, they’ll still have to “go through a complete bowel clean out which is what seems to upset them more than anything else”.

Other measures have been taken to try and improve colonoscopy access, with independent endoscopy nurses attempting to fill the gap. Yet, a position statement released by the Gastroenterological Society of Australia and covered by the limbic suggested the move was “misguided” and unnecessary.

“There are sufficient specialist gastroenterologists and surgeons, and colonoscopists-in-training, to meet current and future demand in metropolitan and regional centres,” the statement read, suggesting that any shortcomings to Australia’s endoscopic services were due to “inadequate infrastructure and underfunding, not lack of endoscopists”.

Like nurse-administered endoscopy, widespread CTC uptake would require an expansion of dedicated expertise, the communication read.

Nonetheless, the procedure “is a safe and accurate tool for CRC screening in both asymptomatic and symptomatic patients” and could help relieve pressure on endoscopic services, it concluded.

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