Age-related differences in progression patterns, follow-up strategies, and postoperative outcomes in locally advanced rectal cancer: insights from a large-scale validated study.

Background: Locally advanced rectal cancer (LARC) presents significant treatment challenges, particularly as patient age may influence disease progression and treatment response. Understanding the differences in progression patterns and treatment outcomes between older patient (OP) and non-older patient (NOP) is essential for tailoring effective management strategies.

Objectives: We aimed to explore the differences of progression pattern, postoperative treatment, and survival outcome between OP and NOP groups in LARC.

Design/methods: The random survival forest model was used to determine the probability of time-to-event occurrence every 3 months. Patients in the NOP and OP group were both categorized into three risk groups based on progression-free survival nomogram scores. We employed inverse probability of treatment weighting (IPTW) analysis and the Surveillance, Epidemiology, and End Results (SEER) database to verify our findings.

Results: Our results revealed that Groups 1, 2, and 3 experienced peaks in progression within the first 24 months in NOP group. As for OP group, Group 4 reached a progression peak at the 18th month, Group 5 at the 12th month, and Group 6 at the 9th month. In NOP group, high-risk patients who underwent postoperative chemotherapy had significantly improved overall survival compared to those who did not. Additionally, postoperative chemotherapy did not significantly improve prognosis for patients in low-, moderate-, or high-risk groups of OP group. Finally, the validation results of IPTW analysis and SEER database showed compliance with our findings.

Conclusion: For NOP group, we recommended close follow-up during the first 2 years. As for OP group, it was suggested to conduct close follow-up at the 18th, 12th, and 9th month for low-, moderate-, and high-risk groups, respectively. Furthermore, postoperative chemotherapy can provide survival benefits for patients in high-risk group of NOP group. However, OP group patients should be informed that the potential benefits of postoperative chemotherapy may be minimal.