Purpose: Analysis of biological samples in large cohort studies may provide insight into the mechanism of, and risk factors for, disease onset and progression.
Methods: This study describes the methods used to collect biological samples from a large multi-center cohort of childhood cancer survivors and siblings of childhood cancer survivors and evaluates the predictors of a positive response among these individuals.
Results: Among survivors, female sex, white race/ethnicity, college graduation, never smoking, accessing the healthcare system in the past 2 years, and having a second malignant neoplasm were the strongest predictors of returning a sample. Among siblings, a similar demographic profile defined those likely to submit the requested sample.
Conclusion: To reduce selection bias and increase the value of these samples for future analysis, additional phone calls and reminders targeting non-responders are needed to improve response rates among those least likely to respond to a single mailed request.