The Primary Goal is to conduct a 12 week pilot randomized controlled trial (RCT) of the Fitbit Flex, a popular, affordable, wearable physical activity tracking device, and the Fitbit mobile health (mHealth) app. The target population will be cancer survivors 18-39 years old recruited from the Seattle Cancer Care Alliance. For the intervention group, peer influences will be engaged via a private, social network (e.g. a Facebook group) customized for survivors. Measurements will be completed (1) at baseline, prior to randomization, and (2) during the final week of the intervention period (follow-up measure). This pilot study will provide initial proof of concept and allow for further customization of the intervention for cancer survivors in anticipation of a future, larger proposal to study physical activity and related outcomes over a multi-year period.

Besides conducting exploratory analyses of primary and secondary outcomes for this pilot RCT, we also specify feasibility criteria including: (1) recruiting 50 cancer survivors ages 18-39 years and between 1.0-5.0 years from the completion of active cancer therapy, (2) intervention participants wear the Fitbit Flex on the majority of all intervention days during the 12-week intervention period, and (3) ≥75% of all participants complete online questionnaire data collection at Time 1 and Time 2.

Inclusion Criteria:

• Does not meet recommended guidelines for physical activity (PA,150 min of moderate activity or 75 min of vigorous activity)
• Currently between 1.0-5.0 years from the completion of active cancer therapy
• Able to read and speak English
• Have a smart phone (or can borrow a study-provided iPod Touch) and willing to use it for the mobile app and Facebook group

Exclusion Criteria:

• Pregnant or planning on becoming pregnant in the next year