Can a smartphone app help young cancer survivors get moving and improve their quality of life?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: For YACS * Diagnosis of nonmetastatic cancer (except non-melanoma skin cancer) within 5 years from the time of screening / study overview session * Age Diagnosis of cancer between 18-39 years at time of diagnosis and at time of screening / study overview session * Three or more months post-completion of primary treatment (i.e., surgery, chemotherapy, and/or radiation); may still be undergoing endocrine or hormone therapies * Score of 0 on two of the Exercise Preparticipation Health Screening Questionnaire items or willingness to obtain medical clearance from a primary care physician or oncologist * Self-report engagement in \<60 minutes total each week of MVPA at time of screening / study overview session * Ownership of a smartphone that is either an iPhone (version 5 or greater) or an Android (version 5.0 or greater) * Internet access * Fluency in spoken and written English * Willingness, at time of screening / study overview session, to find a Buddy (someone who knows about their cancer and participation in this study and who is willing to participate by supporting them during the 6-month study), if assigned to that condition For "Buddies" * Friend, co-worker, caregiver or family member of a participating YACS * Age 18 years or older * Score of 0 on the Exercise Preparticipation Health Screening Questionnaire or willingness to obtain medical clearance from a primary care physician * Ownership of a smartphone that is either an iPhone (version 5 or greater) or an Android (version 5.0 or greater) * Internet access * Fluency in spoken and written English * Willingness to share their Fitbit data with the study team Exclusion Criteria: * For YACS: Diagnosis of non-melanoma skin cancer * Absolute contraindications to exercise (i.e., acute myocardial infarction, severe orthopedic conditions), metastatic disease, or planned elective surgery * Currently pregnant or plans to become pregnant in the next 12 months * Plans to move out of the United States in next 18 months * For YACS: Current enrollment in another dietary or physical activity trial * Inability to provide informed consent * Prisoners or other detained individuals