Background: Prevention of cancer in primary care has focused on modifying behaviours associated with increased risk of cancer (primary prevention) or increasing participation in national cancer screening programs (secondary prevention). On the basis of metaanalyses of large prevention trials, a new paradigm in primary prevention – chemoprevention – is beginning to enter the realms of primary care for specific populations.
Objectives: In this article, we discuss two examples of cancer chemoprevention relevant to general practice: low-dose aspirin for the prevention of colorectal cancer in people aged 50–70 years, and selective oestrogen receptor modulators (SERMs) for women at increased risk of breast cancer. We present new expected frequency trees that show the absolute benefits and harms of taking these medications in specific populations.
Discussion: These expected frequency trees can serve as risk-communication aids to support shared decision making and the implementation of new chemoprevention guidelines in general practice.