"While you are on chemotherapy…": common recommendations that lack evidence and may cause harm.

Patients on chemotherapy often use multiple resources to obtain information on wide-ranging issues including prognosis, treatments, diet, exercise, and safety precautions. Websites from national and international cancer organizations are a common source of information. In this commentary, we discuss the strength of evidence associated with some common recommendations, and provide examples of the unintended consequences of some of this advice. We hope this commentary will stimulate more careful consideration of the risks and benefits when drafting these patient-facing materials.