In recent days, the audiences of reputable media outlets have been warned of an “alarming” increase in bowel cancer in young people.
The ABC reported that:
“Australian oncologists are warning that young people are developing bowel cancer at alarming rates. Figures collated by Bowel Cancer Australia over the past 20 years reveal the number of bowel cancer cases found in people aged between 20 to 34 has risen 64%….”
The Sydney Morning Herald reported that: ”
The incidence of bowel cancer in young people has surged in the past decade, more than doubling in some age categories, but doctors have been unable to explain the increase….”
The Herald Sun reported that:
“The incidence of bowel cancer — and deaths — is rising more rapidly in younger people than in any other age group, Australian Institute of Health and Welfare data shows…”
But it was impossible to work out just how alarmed to be as a result of these alarming reports.
None of the media reports that I saw gave details about the absolute number of cases in young people, or the actual rates of diagnosis in young people — ie cases per 100,000 population, for example. Simply reporting the relative increase can give a misleading picture.
The Bowel Cancer Australia press release, which seems to have generated the coverage, doesn’t help much as it also omits such figures.
You had to dig deep into the bowels of the release (sorry) to find a belated acknowledgement that bowel cancer — like most cancers — is most common in people over 50. There also was presumably the reason for the timing of the release: Bowel Cancer Awareness Week (5-11 June).
Fortunately that new media adage about the “audience knows best” was beautifully illustrated when I put up a Croakey post last night drawing attention to the lack of useful information being provided by the media and experts.
One reader got in touch with links to the relevant Australian Institute of Health and Welfare data (the Australian Cancer Incidence and Mortality books) which put the story into a somewhat less alarming context than the headlines, showing that:
- Of 58,926 people who were diagnosed with bowel cancer between 1997-2001, 92 people were under 25 (0.16%) and 418 were aged 25-34 (0.71%).
- Of 64,829 people who were diagnosed with bowel cancer between 2002-2006, 150 people were aged under 25 (0.23%) and 465 were aged 25-34 (0.72%).
Another reader, a GP in WA, Dr Brett Montgomery, then went to the effort of compiling the AIHW data into this graph:
“I decided to make a graph from the data looking at the trend over time in the proportion of people with newly diagnosed bowel cancer who are under 35. The graph seems to be at its lowest in approximately 1992-1997. The proportion of bowel cancers occurring in young people seems to have increased since then, but not to a level out of keeping with historical patterns. I have included all the years for which data is available at ACIM — I haven’t cherry-picked a particular starting point.
“I don’t know if this graph demonstrates a true mid-90s dip in proportion of bowel cancers in younger people or if this appearance might all be due to chance. You would need someone more statistically savvy than myself to calculate that. However, I hope this graph might help put things in a useful perspective.
“It is interesting that the authors of the press release chose the nadir of this graph as their baseline in their comparisons. If they had instead used the period 5 years earlier, 1987-1991, their press release may not have captured the same media attention.”
In other words, Montgomery’s analysis (which as he acknowledges merits further review) suggests there has actually been a slight decline in the proportion of bowel cancers occurring in people under 35, depending on which time frame you examine.
I have asked Bowel Cancer Australia for clarification but have not yet heard back. Any response will be added to the Croakey post.
Rather than being a familiar and depressing story about experts and media letting down their audiences, perhaps the more uplifting take from this story is the power of an informed and engaged audience. And that’s a message that has import far beyond media organisations…