Early prevention, early detection and early treatment of lung cancer can help reduce the incidence and improve the survival rate.Chemoprevention is known to have an important role in high-risk people because it has the potential to prevent or reverse the progression of lung cancer.Lung nodules are good targets for testing the efficacy of chemopreventive agents.So far，none of the chemopreventive agents have been shown to be effective.~Limonene is widely found in the essential oils of traditional Chinese medicine tangerine peel, green peel and other plants. Its taste is sour, sweet and pungent. It has an aromatic odor effect. Limonene Capsule, a Chinese patent medicine, has been on the market, which is suitable for the treatment of cholecystitis, cholangitis, cholelithiasis, and postoperative biliary syndrome.Preliminary studies of the research group suggest that it has a potential anti-cancer effect.~This randomized, double-blind, controlled trial studied limonene compared with placebo in treating high-risk patients with pure ground glass pulmonary nodules，so as to expand indications.
The prevention and treatment of lung nodules involves many fields in preventive medicine and clinical medicine. A nodule is a growth or lump that may be malignant (cancer) or benign (not cancer). This study is aim to investigate the chemopreventive effect of limonene in inhibiting the occurrence/progression of ground glass pulmonary nodules. It is expected that limonene can be used as a safe and effective chemopreventive agent for preventing the development/progress of pulmonary nodules as well as expanding the indications of limonene.