Treatment Sequences in Patients with Metastatic Colorectal Cancer in Japan: Real-World Evidence of First- to Fifth-Line Treatments

<b>Background:</b> The development of later-line drugs for metastatic colorectal cancer (mCRC) has expanded treatment options. However, real-world evidence of treatment sequences and transition rates from early- to later-line treatments are limited. <b>Patients and methods:</b> This was a retrospective study using hospital administrative data from patients in Japan who underwent colorectal cancer surgery or first-line treatment after January 2017. Transition rates were calculated and treatment sequences were summarized using a Sankey diagram. Logistic regression was performed to identify factors associated with the transition from second- to third-line treatment. <b>Results:</b> In total, 27,100 patients (median age: 69 years) were included in the study population. Transition rates to subsequent treatment lines from first to fifth ranged from 66.6% to 71.3% (first to second: 69.4%; second to third: 71.3%; third to fourth: 71.1%; fourth to fifth: 66.6%). Among 9061 patients who received second-line treatment, 6456 continued to third-line treatment, and 2605 received the best supportive care. Longer first- (≥180 days; OR: 1.24; 95% CI: 1.13-1.37) and second-line (≥120 days; OR: 1.70; 95% CI: 1.55-1.86) treatment durations were significant factors for continuing to third-line treatment. Prior therapy with oxaliplatin and irinotecan plus molecular targeted drugs was also associated with a higher likelihood of proceeding to third-line treatment (OR: 1.41; 95% CI: 1.27-1.56). <b>Conclusions:</b> This study describes the current mCRC treatment landscape in Japan. Considering the findings, appropriate early treatments are critical for transition to later-line treatment. Additionally, many later-line options are necessary to provide treatment continuation opportunities for better outcomes.