This is a prospective observational study designed to determine the feasibility and acceptability of objectively measuring physical activity, sedentary time, and sleep using the Fitbit Charge HR wristband. 50 patients who have been diagnosed with breast cancer and are planning to initiate chemotherapy will be invited to participate in this study, and we will measure general and breast-specific quality-of-life using Patient-Reported Outcomes Measurement Information System (PROMIS) measures for 3-6 months after completion of chemotherapy.

Over 3.1 million women are currently living with a diagnosis of breast cancer in the United States (US), representing 41% of all female cancer survivors in the US. The increased breast cancer survival rate has necessitated a shift in cancer care toward developing interventions to empower patients to improve their quality-of-life, and perhaps prognosis, during and after treatment. Among women diagnosed with early-stage (I or II) breast cancer, around 40% will receive chemotherapy. Among women diagnosed with late-stage (III or IV), around 75% will receive chemotherapy. Adjuvant chemotherapy is associated with many side effects, including fatigue, nausea, disturbed sleep, decreased activity, and weight gain. Women receiving chemotherapy gain an average of 2.5 to 6.2 kg during therapy. Weight gain increases the risk of breast cancer recurrence and mortality, as well as cardiovascular disease, diabetes, and second primary cancers. Physical activity alleviates or reduces both short and long term treatment side effects of chemotherapy, including weight gain, and restores physical functioning in breast cancer patients. Additionally, randomized controlled trials in breast cancer patients have shown that adding exercise to chemotherapy programs can improve breast cancer outcomes.

Although there are many benefits of engaging in physical activity during cancer treatments, activity levels typically decline throughout treatment. Existing research has relied on self-reported activity levels, which is a poor measure of low-intensity activities and can only capture a periodic snap shot of activity levels. This study will provide objective physical activity data across the entirety of the patient's chemotherapy treatments. This in depth data will provide a new perspective on the patterns of activity levels and help to identify if there are critical times in which to intervene to prevent physical activity declines.

Inclusion Criteria:

• have been diagnosed with breast cancer
• be planning to initiate chemotherapy for breast cancer at University of California, San Francisco (UCSF)
• be able to speak and read English, or have a family member or friend who can assist in translating and completing surveys in English
• be able to walk unassisted
• be able to navigate websites, fill out forms on the web, communicate by email, and have regular access to the internet

Exclusion Criteria:

• We will exclude individuals who cannot speak or read English unless they have a friend or family member who can assist in translating and completing quality of life surveys in English. In addition, the Fitbit® requires the ability to connect to the Internet and input data in a website, therefore we will exclude patients with no regular access to the Internet or who are unable to fill out forms on the web or navigate websites. We will exclude patients who are unable to walk unassisted.

Potentially eligible patients who are planning to initiate chemotherapy for breast cancer will be identified through the Breast Care Clinic. Our power calculation is based on the proportion of patients who successfully complete the study, defined as ≥70% of participants wearing the Fitbit and completing the post-chemotherapy follow-up assessment. Using a 1-sided 1-sample binomial test with α = 0.05, 50 patients, an expected successful completion proportion of 70%, we will have 80% power to reject the null hypothesis if 53% or fewer participants successfully complete the protocol. In other words, the intervention will be considered feasible if 27 or more participants in complete the protocol.