Background: Childhood cancer survivors (CCS) are at elevated risk of chronic health conditions. Chemotherapies can cause recurrent acute kidney injury which may progress to kidney fibrosis, chronic kidney disease (CKD) or hypertension (HTN). CCS surviving to adulthood are at ≥3 times the risk (vs. non-CCS) for CKD, HTN and lower quality of life. However, the timing of CKD and HTN onset in CCS completing cancer therapy in childhood remains unclear.

Guidelines provide recommendations on managing post-cancer therapy effects in CCS, but they lack specificity on kidney testing content, frequency and complications. This discord is largely due to knowledge gaps on which CCS develop CKD or HTN after cancer therapy, when outcomes occur and their severity. Existing work has shown in select patients, CKD and HTN in CCS likely begins in the first 5 years post-cancer therapy and that the burden is significant. With robust data on CKD and HTN, international CCS follow-up guidelines can be optimized to include detailed and actionable recommendations on kidney and blood pressure monitoring and treatment.

Significant improvements in childhood cancer survival rates have come at the cost of an increase in chronic health conditions. Childhood cancer survivors (CCS) often experience chronic kidney disease (CKD) and hypertension (HTN), yet data on the onset and severity of these diseases in the primary years after childhood cancer therapy is unclear. Both CKD and HTN are major treatable cardiovascular risk factors, and the knowledge gap in the first 5 years after therapy impedes the creation of evidence-based guidelines and early intervention plans.

Currently, the Children's Oncology Group international guidelines, which are used to identify and manage therapy effects in CCS, lack information on CKD testing and appropriate measures. With appropriate treatment, CKD and HTN complications are treatable.

In 500 CCS at high risk for blood pressure (BP) and late kidney effects due to cancer therapy, we will determine the prevalence of HTN and CKD at 3 and 5 years after cancer therapy, and the extent to which eGFR, albuminuria and BP worsen from 3 to 5 years after therapy. In addition, we will assess whether acute kidney injury during cancer therapy and cardiometabolic risk factors are associated with these outcomes.

Based on the evidence from the study, we hope to improve current CCS kidney and BP guidelines to advise on appropriate treatments and measures for HTN and CKD. As CCS are vulnerable to cardiovascular disease, addressing CKD and HTN complications will improve their overall quality of life.

Inclusion Criteria:

• 3 years ± 6 months after therapy for first cancer
• Received high-risk therapy for first cancer, as defined by the Canadian Oncology Group (COG) as alkylating agents; platinums; abdominal or total body radiation; high dose methotrexate; stem cell transplant; nephrectomy; or other therapy which may be known to possibly cause late kidney and/or BP effects.

Exclusion Criteria:

• Pre-cancer severe CKD and/or previous kidney transplant
• >19 years old at 3 years after cancer therapy completion

Observational cohort study of CCS at 5 Ontario child cancer centres