Bowel cancer screening participation rate in a program that offers blood tests as well as faecal tests as screening options.

INTERVENTION: The intervention is a bowel cancer screening program that includes the availability of a screening blood test after an offer of the standard faecal occult blood test (FOBT). There are two intervention groups (n = 600 per group). Everyone in the intervention will be initially mailed an offer of screening for bowel cancer by FOBT. For the first intervention group, after 12 weeks anyone who has not participated with the FOBT will be mailed an offer of screening for bowel cancer by blood test (the methylated BCAT1/IKZF1 blood test). They will then need to call the study helpline to request a further blood test information. The second intervention group will be sent the offer for the blood test at the same time as receiving the FOBT. They will be advised that if they believe that the FOBT is not suitable for them they might consider screening for bowel cancer by blood test. They will then need to call the study helpline to request a further blood test information. Anyone requesting the blood test will then be sent information about the test (including accuracy of the test, where they can get their blood collected, and when they will receive their test results) and a test referral. They can then take up the offer of the free screening blood test at one of 10 local blood collection centres (Healthscope). They do not need to be fasted and appointments do not need to be made. Reminder letters will be sent to non‐participants 6 weeks after each type of screening test offer. Participants of the FOBT will be required to collect a small sample from two separate bowel movements. These samples are then sent via reply‐paid mail to a laboratory which tests the samples for the presence of blood. If more than 100ng/mL of blood is present in either sample, than the participant will be sent a positive result letter (which will be copied to their GP) to advise further investigations. Participants of the blood test will need to attend a Healthscope collection centre and have 18mL of blood collected. This will be sent to a laboratory for analysis. If methylated BCAT1 or IKZF1 are detected in the blood sample then the participant will be sent a positive result letter (which will be copied to their GP) to advise further investigations. Total screening participation rate with either the FOBT or the blood test will be assessed at 24 weeks after the start of the study (12 weeks after the blood test offer). Round 2; to examine participation and re‐participation over two rounds of colorectal cancer screening offers. The same cohort (participants and non‐participants who did not withdraw/opt‐out from the study) will be contacted in this Round. This will assess whether non‐participants can be encouraged to participate by offering more choice of test up front, thereby ‘rescuing’ people who may not participate from a single screening offer, or from a FOBT offer only. CONDITION: Colorectal cancer PRIMARY OUTCOME: Total participation rate in a bowel cancer screening program that offers a FOBT followed by a blood test, compared to a program that only offers FOBT. This will be assessed at the 24 week timepoint by review of laboratory records. SECONDARY OUTCOME: Screening participation rate with a blood test compared to a second offer of a FOBT. This will be determined by review of laboratory records. The proportion of people who can not participate with FOBT due to medical conditions. This will be determined through the review of feedback from participants‐ either from their mailed feedback or from their comments to the study helpline. To determine rates of participation adherence for those who participated in the first round of screening, with either the FOBT or the blood test. To investigate whether a second round of screening offer of blood test or FOBT can encourage participation among those who did not participate in the first round. The participation with the blood screening test versus FOBT will be analysed. INCLUSION CRITERIA: Randomly selected South Australians from the Australian Electoral Roll, aged 50‐74y.