chemoprevention

Chemoprevention refers to the use of natural or synthetic chemical agents to prevent, halt, or reverse the development of cancer before it becomes clinically invasive. The field encompasses primary prevention, which aims to lower cancer incidence in at-risk populations, and secondary prevention, which targets premalignant lesions or early neoplasia to reduce progression or recurrence.

Agents studied include selective estrogen receptor modulators (SERMs) such as tamoxifen and raloxifene for reducing breast cancer risk in high-risk women; aromatase inhibitors; nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and sulindac for colorectal cancer prevention; and various vitamins, minerals, and phytochemicals. The evidence base is strongest for certain contexts, notably tamoxifen or raloxifene reducing risk of estrogen receptor–positive breast cancer in high-risk individuals, and aspirin reducing incidence and mortality from colorectal cancer in some populations. Trials, experimental and observational data also explore curcumin, green tea catechins, and other natural compounds, though effects are less consistently demonstrated in randomized trials.

Clinical use requires careful risk-benefit assessment because agents can cause adverse effects such as thromboembolism and endometrial cancer with SERMs, or gastrointestinal and cardiovascular toxicity with NSAIDs and COX inhibitors. Trials often rely on cancer incidence or recurrence as endpoints and may use surrogate biomarkers.

Challenges include heterogeneity of cancer risk, long latency periods, and balancing population benefits against individual harms. Ongoing research seeks to identify high-risk groups, optimize agent selection, and develop safer, targeted strategies with improved efficacy.