Treatment sequences in patients with metastatic colorectal cancer in Japan: Real-world evidence of 1 ^st - to 5 ^th -line treatments.

76 Background: The development of later-line drugs for metastatic colorectal cancer (mCRC) has expanded treatment options for systemic chemotherapy in patients with mCRC. However, few studies have investigated patients who received later-line treatment in a real-world setting, and available information on treatment sequences and transition rates from early- to later-line treatments is limited. Methods: This was a retrospective study using hospital administrative data collected by MDV (Medical Data Vision, Tokyo, Japan) from April 2008 through February 2023 in Japan. Treatment regimens were derived from standard treatments recommended in the Japanese guidelines. The study population was determined using an algorithm from a similar study previously conducted in Japan. Our analysis focused on patients who started CRC surgery or 1 st -line treatment after January 2017 to reflect recent late-line real-world practice. Transition rates from 1 st - to 5 th -line treatment were calculated, and treatment sequences were summarized using a Sankey diagram. Logistic regression was performed to identify the factors associated with the transition from 2 nd - to 3 rd -line treatment. Results: A total of 722,005 patients with a CRC diagnosis record were identified in the MDV database. Of these, 26,456 patients were included in the study population. The median age was 69 years and 61.4% of patients were male. The rates of transition to subsequent lines from 1 st to 5 th line ranged from 65.7% to 70.4% (1 st to 2 nd 68.3%; 2 nd to 3 rd 70.4%; 3 rd to 4 th 69.9%; 4 th to 5 th 65.7%). Among 8528 patients who received 2 nd -line treatment, ~70% of patients (6006) continued 3 rd -line treatment, and 30% of patients (2522) received best supportive care. Comparing these 2 patient groups, younger age (<65 years, OR: 1.50, 95%CI: 1.35-1.67; p<0.001) and longer treatment durations of 1 st (≥180 days, OR: 1.26, 95%CI: 1.14-1.39; p<0.001) and 2 nd (≥120 days, OR: 1.67, 95%CI: 1.52-1.84; p<0.001) lines were significant factors for 3 rd -line treatment continuation. Prior therapy with oxaliplatin or irinotecan plus molecular targeted drugs was also associated with a higher likelihood of proceeding to 3 rd -line treatment (OR: 1.42, 95%CI: 1.28-1.58; p<0.001). Conclusions: In this study, ~70% of patients were able to transition to subsequent lines at the time of each line transition. However, 30% of patients were unable to continue treatment in real-world practice. To increase treatment continuation rates and maintain patient quality of life, new treatment options and further research are necessary to meet patients’ treatment needs, especially in the later-line treatment setting where unfavorable effects from previous treatments are accumulated.