Give patients exact results, urges society
less sensitive test threshold for the national pilot had been used, about 142 of those people would not have had cancer detected.
The ministry has resisted releasing interval cancer figures, repeatedly refusing to do so last year and only releasing them this year after the matter went to the Ombudsman.
Lane emphasised that the interval cancer figures given were provisional as full analysis of the information was not complete. A comprehensive report is expected on the negative Fit results late this year but the colonoscopy data will take longer to compile as the interval between a clear colonoscopy and a return to screening is five years.
Lane said the colonoscopy data released was raw data which had not been confirmed, reviewed or evaluated and any inferences made based on it may be unreliable. It might not include all cancers that had occurred. “Any comparison to . . . international bowel screening programmes cannot be made based on this raw data.”
With regard to the negative Fit interval cancers, it was “very likely numbers will change as the full analysis is completed and reviewed”.
“There are a number of factors why an individual may develop an interval cancer: the cancer was ‘missed’ on the first screen, the cancer wasn’t visible at the first screen, and cancers becoming detectable and symptomatic after the screening.”
Lane said the pilot produced a pronounced shift in the proportion of patients diagnosed with early stage cancer, with 39 per cent of cancers found at stage 1 in the pilot, compared with 13 per cent found at this stage in the unscreened population.
Asked whether these figures were likely to be replicated in the national programme with its increased threshold and the change in the age of those screened, Lane said this was unknown at this time. Bowel screening information should tell people how to get their actual reading, Bowel Cancer New Zealand says.
Results from the programme’s initial test, the faecal immunochemical test, are routinely reported as positive or negative with participants and their family doctors not advised if traces of blood are found below the 200ng haemoglobin/ml buffer solution threshold which would trigger referral to colonoscopy.
Participants can seek this information from the laboratory through their GP, but no process for doing this has been established and participants are not told about this.
The panel which conducted the independent assurance review of the national bowel-screening programme recommends this issue should be further considered.
BCNZ spokeswoman Professor Sarah Derrett said the organisation wants the numerical information to go automatically to GPs.
“We would like to see GPs getting this reading as a matter of course . . . as it will allow them to better monitor their patient should they present with further symptoms.”
Federation of National Women’s Health Councils co-convener Barbara Robson said the report from the independent panel clearly stated a lower number of cancers would be detected in the national programme, with its significant increase to the threshold before referral to colonoscopy and the restricted age range, compared with the pilot.
The reporting issue emerged in 2015 when the National Screening Advisory Committee raised major concerns about plans not to report full initial faecal blood results to GPs, given the change in the test threshold in the national programme.
However, in April last year the committee accepted ministry arguments against this and relented.
Among the arguments the ministry put forward were that it would depart from accepted international practice, it could be misleading and could add to anxiety.