Two landmark cancer screening trials reported this week. They share a finding that sits awkwardly alongside how screening is often discussed: finding cancer early and preventing death from cancer are not the same thing. That gap matters — for how we talk about screening, for how we make decisions about it, and for what we are actually trying to achieve.

The colonoscopy trial

A randomised trial across Norway, Poland, and Sweden enrolled 84,583 adults aged 55 to 64 and followed them for 13 years. Half were invited to colonoscopy screening; the other half received usual care with no invitation.

The results on cancer detection were clear. The screening group had a 19% relative reduction in colorectal cancer incidence — a real, meaningful difference. Colorectal cancer rates: 1.46% in the screened group versus 1.80% in the unscreened group.

The results on mortality were not. After 13 years, colorectal cancer deaths were 0.41% in the screened group and 0.47% in the unscreened group — not a statistically significant difference.

There were other nuances. The reduction was more pronounced in distal colon and rectal cancer than proximal colon cancer. The benefit was larger in men than women. And the control group’s mortality rate was lower than researchers expected — which may have made it harder to detect a mortality difference, even if one exists.

The Cochrane PSA review

The updated Cochrane systematic review of PSA screening pooled data from six randomised controlled trials, covering approximately 790,000 men aged 45 to 80, mostly from Europe and North America.

PSA screening produced a 13% relative reduction in prostate cancer mortality — roughly two fewer prostate cancer deaths per 1,000 men screened. PSA screening also significantly increased cancer detection, particularly early-stage disease.

All-cause mortality: no significant difference between screened and unscreened groups.

The review notes that newer approaches combining PSA with kallikrein panel markers and MRI triage show promise, with better specificity and fewer unnecessary biopsies, but long-term mortality data for these refined approaches are not yet available.

What this means for Australian practice

It is worth being clear about what these results do and do not change.

Australia’s National Bowel Cancer Screening Programme uses the immunochemical faecal occult blood test (iFOBT), not colonoscopy as the primary screening tool. The colonoscopy RCT above is studying something different — colonoscopy as a first-line population screening tool, not the colonoscopy used when an iFOBT comes back positive. Those are different clinical contexts. The NordICC trial does not speak directly to whether the Australian approach works.

For PSA: the RACGP position is shared decision-making for men aged 50 to 69 who want to know their options — not universal screening, but not discouragement either. The Cochrane finding of prostate cancer mortality reduction without all-cause mortality benefit is the evidence that grounds that nuanced position. It is not evidence that PSA screening is pointless; it is evidence that PSA screening is complex.

Both-and

Screening does detect cancer. That is not trivial. A 19% relative reduction in colorectal cancer incidence is a real finding. Two fewer prostate cancer deaths per 1,000 men is a real finding. The question is whether detecting more cancer early translates into living longer — and both of these trials suggest the answer is more complicated than the word “screening” alone implies.

Overdiagnosis — detecting and treating cancers that would never have caused symptoms or death — is a genuine phenomenon in both prostate and colorectal cancer screening. Some early-stage cancers detected by screening grow slowly enough that treatment during a person’s natural lifespan would not have been necessary. When that happens, screening and its downstream treatment cause harm without benefit. The difficulty is that we cannot identify in advance which detected cancers fall into that category.

The honest answer to “should I get screened?” is: it depends on the screening type, the cancer, the population, and what you value. For bowel cancer via iFOBT: the Australian evidence and programme support participation — the NBCSP has a documented impact on bowel cancer mortality. For PSA: a conversation with your GP about what a positive result would mean, and what you would want to do with that information, is the right starting point.

One more story: ovarian cancer immunotherapy

The same Medical Republic round-up covered early Phase 1 results for AVB-001 — an implantable device delivering engineered cells that produce interleukin-2 locally, tested in 14 patients with platinum-resistant ovarian cancer. Several patients had disease stabilisation; around half experienced temporary progression halt; no dose-limiting toxicities. These are very early results (Phase 1, 14 patients, single study), not yet practice-changing, but the local interleukin-2 delivery approach is an interesting direction for a cancer with limited options at platinum-resistant stage. Worth watching.

My two cents

The detection-versus-mortality gap is not an argument against screening. It is an argument for being honest about what screening does and does not promise.

The patients who ask me whether they should complete their bowel screening kit, or whether their husband should have a PSA test, are asking a reasonable question. The answer is not “screening is a waste of time.” The answer is “here is what the evidence shows, here is what a positive test would mean in practice, and here is what you would be deciding to do about it.” That conversation cannot be replaced by a blanket recommendation in either direction.

If you are aged 50 to 74 and have not completed your NBCSP bowel screening test in the last two years, that is the most straightforward evidence-backed action available to you in the Australian context. The programme uses iFOBT, which has a different evidence base from the colonoscopy trial discussed here — and the Australian data on NBCSP participation and mortality are separate and supportive of the programme.

For PSA: bring the question to your GP. That is what shared decision-making looks like in practice.

Verdict: maybe — the evidence base for these screening approaches is real and contested in ways that matter for informed decision-making; this changes how we discuss screening, not whether it happens.

Colonoscopy and PSA: the gap between detection and survival