PurposeTo identify the initiation or discontinuation of complementary therapy (CT) and determine the impact of sociodemographic and clinical factors on CT use among cancer patients.Patients and MethodsEligible patients were age 20 or older; newly diagnosed with stomach, liver, or colorectal cancer; and started their initial treatment at the National Cancer Center, Korea, between April 1, 2001, and April 30, 2003. In total, 541 cancer patients were surveyed in face-to-face interviews at baseline, and telephone follow-up interviews were performed every 3 months for 3 years.ResultsA total of 281 patients commenced CT after diagnosis; 164 patients stopped using CT during the follow-up period. The overall cumulative probability of starting CT at 1, 2, and 3 years was 50%, 54%, and 55%, respectively. In a Cox multivariate analysis, stomach and liver cancer were associated with an increased probability of initiating CT compared with colorectal cancer. Patients who were classified as stage I, II, or III at diagnosis were associated with a decreased probability of discontinuing CT compared with stage IV.ConclusionMost cancer patients started to use CT during the initial treatment period. Thus, physicians should communicate with cancer patients about CT at this phase. In particular, more attention should be paid to women and individuals with higher household incomes because these groups are more likely to start CT.