The Prognostic Significance of Postoperative Adjuvant Chemotherapy in the Population Aged 75 Years and Older with Stage II-III Colorectal Cancer: A Retrospective Multi-Center Cohort Study

Background: It is common for elderly patients to be underrepresented in clinical trials for cancer, which can result in a lack of efficacy data and unclear criteria to guide treatment decisions for clinical doctors. Therefore, one of the common challenges in oncology treatment is determining the extent to which patients aged 75 and older have benefited from postoperative chemotherapy. Purpose: The study aimed to explore the effect of adjuvant chemotherapy (AC) on 3-year recurrence-free survival (RFS) after curative resection in patients aged 75 years and older with stage II-III colorectal cancer (CRC). Methods: The retrospective cohort analysis was performed on patients with stage II-III CRC who received curative resection at three cancer centers in China between 2008 and 2017. Kaplan-Meier curves and Multivariable Cox regression models were used to analyze the impact of AC on RFS in patients. Finally, propensity-score matching was used to reduce selection bias and confounding factors in patients aged 75 years and older with stage II-III CRC. Results: A total of 2885 patients were included (1729 (59.9%) male; 1312 (61.5%) received AC). The pre-matching cohort was comprised of 151 patients aged 75 years and older (median age (IQR)77.00 (76.00, 79.00); 97 (64.2%) male, 51 (72.9%) received AC). Age (P=0.001), postoperative carcinoembryonic antigen (CEA)(P=0.02) level were associated with prognosis. But AC was not associated with 3-year RFS (HR, 1.27; 95% CI, 0.80-2.0; log-rank P=0.37). After a predisposition 1: 1 match (with or without AC, n = 42), AC remains uncorrelated with 3-year RFS (HR, 1.39; 95% CI, 0.52-3.70; log-rank P=0.66). Conclusion: Patients over the age of 75 with stage II-III CRC who receive AC or do not face the same risk of postoperative recurrence. As a result, patients with stage II-III postoperative adjuvant chemotherapy can make an informed decision regarding whether they want to undergo chemotherapy based on their age and reduce the unnecessary side effects of chemotherapy.