IMPORTANCE Population-based East Asian data have corroborated reports from non-Asian settings on the association between low-dose aspirin and a lower risk of colorectal cancer (CRC). OBJECTIVE To evaluate the association between duration and recency of low-dose aspirin use and CRC risk. DESIGN, SETTING, AND PARTICIPANTS This nested case-control study included individuals who initiated aspirin use and matched individuals who did not use aspirin. Data were collected from Taiwan National Health Insurance and Taiwan Cancer Registry from 2000 through 2015. CRC cases were age-and sex-matched in a 1:4 ratio with individuals in a control group, identified from a cohort of individuals who used and did not use aspirin through risk-set sampling. Data analysis was conducted from June 2018 to July 2019. EXPOSURES Low-dose aspirin use was defined as receiving less than 150 mg per day, whereas 100 mg/d was most commonly used. Based on duration and recency of low-dose aspirin use between cohort entry (initiation date of low-dose aspirin for aspirin use group or randomly assigned date for those who did not use aspirin) and index date (CRC diagnosis date for individuals in the case group and the diagnosis date for the 4 corresponding matched individuals in the control group), the 3 following mutually exclusive exposure groups served as the basis for analysis: (1) long-term current low-dose aspirin use, (2) episodic low-dose aspirin use, and (3) no low-dose aspirin use (the reference group). MAIN OUTCOMES AND MEASURES CRC risk among the 3 exposure groups. RESULTS Among 4 710 504 individuals (2 747 830 [51.7%] men; median [interquartile range] age at cohort entry in initiator group, 61 [52-71] years; median [interquartile range] age at cohort entry in nonuse group, 59 [51-68] years), 79 095 CRC cases (1.7% of study cohort) were identified. Compared with no low-dose aspirin use, the adjusted odds ratio (OR) for long-term current low-dose aspirin use and CRC risk was 0.89 (95% CI, 0.85-0.93); for episodic use, 0.88 (95% CI, 0.86-0.89). Adjusted ORs of 0.69 (95% CI, 0.63-0.76) and 0.64 (95% CI, 0.61-0.67) were observed for long-term current use and episodic low-dose aspirin use within the subcohort of individuals who initiated low-dose aspirin between age 40 and 59 years. CONCLUSIONS AND RELEVANCE In this study, low-dose aspirin use was associated with 11% lower CRC risk in an East Asian population, and this association was larger when low-dose aspirin use started before age 60 years.

e24111 Background: Bone is a common metastatic site among patients with advanced lung cancer. With new treatments available to improve survival of lung cancer and in all likelihood to change the natural history of disease, the diagnosis and management of bone metastasis (BM) may be of increasing clinical relevance. This study aimed to describe the management of BM using bone targeting agents (BTA) among lung cancer patients in Taiwan. Methods: A retrospective cohort of lung cancer patients with BM from 2004 through 2016 was identified using Taiwan National Health Insurance (NHI) data and Taiwan Cancer Registry. Diagnosis codes of International Classification of Disease 9th revision (ICD-9: 198.5) and ICD-10 (C79.51 and C78.03) were used to define BM. Patients were followed from the time of BM diagnosis till death or the end of study period (2017/12/31). We ascertained demographic information and BTA use among these patients. Two classes of BTAs were included: bisphosphonates (zoledronic acid (ZA), pamidronate, and clodronate) and denosumab. Results: A total of 44,800 patients with lung cancer and incident BM diagnosis were identified during the study period. Median age at the time of BM diagnosis was 67 years (25th and 75th percentile: 57-76), with 58.2% male (n = 26,058). The annual number of lung cancer patients with incident BM increased from 2,814 in 2004 to 3,829 in 2016, while the proportion of these patients receiving any BTA during the follow-up ranged from 25.2% to 34.8% annually. Clodronate and pamidronate were the common BTA prescriptions, whereas denosumab became the most frequently prescribed BTA after reimbursement by NHI since 2015. Among patients who initiated BTA after BM diagnosis (n = 10,879), the median time from BM diagnosis to BTA initiation ranged from 31 to 152 days by initial BTA type. More than half of them received more than one dose (56.3%, n = 6,126), with median numbers of doses received as 3, 4, 6 and 6 for ZA, pamidronate, clodronate and denosumab, respectively. Conclusions: A large population of patients with lung cancer were diagnosed with BM every year. However, overall, we observed only a small proportion of eligible patients receiving a BTA and a delayed initiation of BTA, indicating suboptimal treatment for lung cancer patients with BM in Taiwan.[Table: see text]