Oncological outcomes in elderly patients with non-metastatic colorectal cancer - a nationwide cohort study

<b>Introduction</b><br/>Increasing life expectancy has lead to more octogenarian (80+ years) colorectal cancer (CRC) patients. This study estimates and compares oncological outcomes in octogenarian CRC patients compared to patients aged 70-79 years (septuagenarians).<br/><b>Material and methods</b><br/>This nationwide cohort study included all +70 years old Danish patients operated for UICC stage I-III CRC between January 2010 and December 2019. Overall survival (OS) was estimated using the Kaplan-Meier method. Recurrence status was determined for patients that were disease-free 6 months postoperative by<br/>applying a validated algorithm to data from nationwide health registries. The 5-year cumulative incidence functions (CIF) of recurrence and subsequent primary cancers were reported, and hazard ratios (Cox proportional hazards regression: HR, 95% CI) adjusted for patient and tumor characteristics were reported.<br/><b>Results</b><br/>Among 14,341 CRC patients, 5,003 (34.9%) were octogenarians. The 5-year overall survival was 50% (95% CI: 49%-51%) in octogenarians compared to 75% (95% CI: 74%-76%) in septuagenarians, HR=2.21 (95% CI: 2.09-2.35). The mortality ratio was highestin the early postoperative phase, with a synergistic effect between age and preoperative performance score assessment. The 5-year CIF of recurrence was 16% (95% CI: 15%-18%) in octogenarians compared to 18% (95% CI: 17%-19%) in septuagenarians, HR=0.94 (95% CI: 0.86-1.03). A smaller fraction of octogenarian recurrences were diagnosed at the timepoints of surveillance<br/>CT scans at 12 and 36 months postoperative (according to Danish guidelines); 24% in 80+ group vs. 30% in septuagenarians. The 5-year CIF of subsequent primary cancers did not diff er between the groups, HR=0.90 (95% CI: 0.78-1.03).<br/><b>Conclusions</b><br/>Short-term mortality was high in octogenarians, while the incidence of recurrence and SPCs were comparable to septuagenarians. Preoperative risk assessment seems important in order to achieve longterm disease-free survival.