Medical Journal of Australia. 2013 198:327-30

Shift to earlier stage at diagnosis as a consequence of the National Bowel Cancer Screening Program

Cole SR1,2, Tucker GR3, Osborne JM1,2, Byrne SE2, Bampton PA2, Fraser RJ2, Young GP2

1Bowel Health Service, Repatriation General Hospital, Adelaide, SA; 2Flinders Centre for Innovation in Cancer, Flinders University, Adelaide, SA; 3Health Statistics Unit, Department of Health and Ageing, Adelaide, SA

 

ABSTRACT:

Objective: To assess the impact of the National Bowel Cancer Screening Program (NBCSP) in South Australia.

Design, setting and participants: A cohort comparison of colorectal cancer (CRC) patient data from the NBCSP register and the South Australian Cancer Registry. Patient records of those invited to take part in screening through the NBCSP, those who participated in the program, and those with positive test results were compared with those of the rest of the study population (excluding the group of interest) on an intention-to-screen basis.

Main outcome measure: Stage of CRC at diagnosis as a surrogate marker for effect on CRC mortality.

Results: Of 3481 eligible patients, 221 had been invited to the NBCSP. Invitees were more likely to have stage A lesions compared with all other patients (34.8% versus 19.2%; P < 0.001), and half as likely to have stage D CRC (5.4% versus 12.4%; P< 0.001). A further shift towards earlier stage was seen in those who participated in screening and those with positive test results compared with all other patients (38.8% stage A and 3.0% stage D in screening participants versus 19.3% stage A and 12.4% stage D in all other patients; and 39.7% stage A and 2.6% stage D in those with positive test results versus 19.3% stage A and 12.4% stage D in all other patients; P < 0.001).

Conclusions: CRCs were diagnosed at a significantly earlier stage in people invited to the NBCSP compared with those who were not invited, regardless of participation status or test result. The NBCSP should lead to reductions in CRC mortality in Australia.

PMID: 23545032

 

SUPPLEMENT:

Diagnosis at an early stage is crucial for survival from colorectal cancer (CRC). In lengthy randomised controlled trials, population screening using faecal occult blood tests (FOBT) resulted in earlier stage at diagnosis and reduced mortality from CRC compared to control populations not offered screening. Since those early trials, FOBTs have been subject to improvement through technological advances that improve their sensitivity for CRC, and that remove inherent barriers to population participation. These newer tests use immunochemical means to detect faecal occult blood and are known as faecal immunochemical tests for haemoglobin (FIT). No randomised trials have been undertaken to determine whether population screening using FIT results in reduced mortality from CRC.

CRC is a major health problem in many western countries. Following demonstration of the efficacy of FOBT-screening on mortality from CRC, the Australian Government introduced the National Bowel Cancer Screening Program (NBCSP), which offers free screening for CRC using FIT technology through targeted invitations to specific age groups in the at risk population (people over 50 years of age),. After the NBCSP had been in operation for several years, the investigators were approached by the Australian Department of Health and Ageing to undertake an evaluation of Program outcomes.

We used stage at diagnosis as a surrogate marker for population mortality as evaluations of cancer prevention programs with mortality as an end point take many years to complete. The South Australian Cancer Registry (SACR) holds up-to-date records of CRC diagnoses in South Australia, including tumour stage. Our approach was to determine whether CRCs diagnosed in people who had been invited to the NBCSP were diagnosed at an earlier stage than CRCs diagnosed in people not invited to the program. Following a lengthy data linking process that satisfied privacy considerations, we combined personally identified data held by the SACR on tumour stage, and invitation, participation and test result status held by the NBCSP register to evaluate the effect of the NBCSP on CRC stage at diagnosis, relative to stage in people who did not receive an invitation.

We found that the CRC stage in the invited population was on average significantly earlier than the CRC stage in the population not invited (i.e. cancers had been down-staged, see abstract for details). As expected, there was a further shift towards earlier stage at diagnosis when the participant group was compared with all other diagnoses and this trend continued when the positive subgroup stage profile was compared to all other diagnoses. There were significant differences in demographic characteristics between groups, however multivariate analyses showed that early stage still associated with being invited when controlling for these differences.

Our findings are consistent with other reports on outcomes from national or regional FOBT-based population screening programs for CRC which all show a shift towards earlier stage in the population participating in screening, although none have objectively compared program outcomes with outcomes in a population not offered screening. We felt it was important to analyse the program in the first instance on this intention-to-screen basis as an impact at such a level demonstrates the value of the public health program and justifies its implementation. Also, it was important to determine that the benefit from screening seen in the randomised trials, often in highly selected populations, is also seen when the research is translated into the real world.

Another interesting finding was that Australia’s NBCSP uses FIT, and this is the first demonstration of down-staging in a mass screening program using this test type. Although at the moment only a proportion of the eligible Australian population is offered screening each year, the proposed gradual expansion of the NBCSP should, over time, result in a significant reduction in CRC mortality. Reduced mortality should also be seen in other countries that have introduced occult blood-based population screening for early detection of CRC.

Acknowledgment

The study was funded by the Australian Government Department of Health and Ageing

Contact Information

Stephen Cole, Bowel Health Service, Repatriation General Hospital, South Australia, +61 8 8275 1838, steve.cole@health.sa.gov.au, or Graeme Young, Flinders Centre for Innovation in Cancer, Flinders University of South Australia, +61 417 860 540, graeme.young@flinders.edu.au.

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