The treatments that aim to cure cancer in children can lead to "late effects" such as second cancers and heart disease. Screening tests can help find late effects, but most adult survivors of childhood cancer do not complete these tests. These survivors are at risk for harm that can be prevented.

The investigators have developed a program called ONLOOP to remind survivors in Ontario, Canada to get the screening tests they need. ONLOOP reminds survivors who are at higher risk for heart disease, breast cancer, and/or colorectal cancer to complete their echocardiograms, mammograms and breast MRIs, and/or colonoscopies.

The goal of this clinical trial is to find out how well ONLOOP helps adult survivors of childhood cancer complete their screening tests. The investigators also want to see if it could be turned into a long-term program in Ontario. Eligible survivors will be randomly assigned to either receive intervention materials or continue with usual care for 13 months before receiving intervention materials.

The intervention includes usual care plus these ONLOOP materials:

1. Study invitation letter and invitation reminder

2. Those who sign up for ONLOOP will receive personalized health information and a screening reminder. Survivors will receive information about:

   1. their cancer treatment
   2. their risk(s) for late effects
   3. the screening tests they should do

3. Participants have the option to provide their family doctor's or nurse practitioner's contact information. For those who consent, the study team will send their family doctor or nurse practitioner a letter with details about their cancer diagnosis and treatment. The letter will also remind them to talk to their patient about their health and screening test(s) needed.

Inclusion Criteria:

• Survivors of childhood cancer who are currently aged 18 and older
• Diagnosed with cancer before age 18 between 1986-2017
• At least 5 years from most recent childhood cancer event (latest of primary diagnosis, relapse, or second cancer before age 18)
• Treated at one of Ontario's five specialized childhood cancer programs
• Received radiation and/or anthracycline treatment that increased the survivor's risk of cardiomyopathy, breast cancer, and/or colorectal cancer
• Overdue for guideline-recommended surveillance by ≥6 months (mammogram and breast MRI, colonoscopy, and/or echocardiogram)

Exclusion Criteria:

• Was not diagnosed or was not fully treated at one of Ontario's five pediatric cancer centres
• Developed a second cancer or relapse of their primary cancer after age 18
• Not currently living in Ontario or address deemed ineligible by Ontario Health
• Opted out of a similar Ontario Health program (eg, the Ontario Breast Screening Program)
• Previously opted out of receiving invitations for Ontario Health research studies or similar communications