Abstract 5179: Comprehensive characterization of rectal cancer reveals less cancer treatment with worse nutritional status and more comorbidities in the older patients

Abstract Background The population aged over 65 years is growing fast. The incidence of most cancers increases with age, and the cancer burden is projected to increase in the future. Colorectal cancer is the second most common cancer worldwide in patients over 65 years. The proportion of rectal cancer has been increasing. Therefore, we specifically characterized the older rectal cancer patients to provide an insight into cancer care for this population. Method A total of 428 and 26,765 patients diagnosed with non-metastatic rectal cancer after 50 years old from a referral tertiary care center (SYSU cohort) and Surveillance Epidemiology and End Results database (SEER cohort) were included in the current study. Patients were categorized by age into intermediate-aged adults (aged 50-65 years, n=223) and older adults (aged≥65 years, n=205). The demographic and clinicopathological features, molecular profiles, treatment strategies, and clinical outcomes were compared between the two groups. The inverse probability weighting method was used to perform risk factors-adjusted survival analysis. Results In the SYSU cohort, the difference between the two age groups was not significant in the clinicopathological features that were reported to be prognostic factors in previous studies, including tumor-node stage, poor differentiation, lymphovascular and perineural invasion and mucinous tumor. In the subset with molecular profiles, the distribution of CpG island methylator phenotype, mutations of KRAS and BRAF, and CD3+ and CD8+ tumor-Infiltrating lymphocyte counts were similar between two age groups. Of note, the older patients had higher prevalence of microsatellite instability (34.3% vs 22.2%, P=0.344). In the whole cohort, the older age was significantly associated with less cancer treatment, including neoadjuvant (6.8% vs 15.2%, P=0.009) and adjuvant (32.7% vs 57.8%, P<0.001) treatment. In addition, significantly lower BMI (median: 21.92 vs 22.92 kg/m2, P=0.004), lower baseline albumin (median: 39.75 vs 41.20 g/L, P=0.003), and higher incidence of high blood pressure (29.3% vs 12.1%, P<0.001) were found in the older patients. Finally, the older patients had significantly worse overall survival outcome (adjusted hazard ratio 2.17 [95% Cl 1.44-3.27, P<0.001]), and this finding was validated in the SEER cohort (adjusted hazard ratio 1.65 [95%Cl 1.58-1.72, P<0.001]). Conclusions Older patients present with more comorbidities and worse nutritional status, and they are less likely to receive cancer therapies. Although older patients had the similar clinicopathological profiles compared with intermediate-aged patients, they had unfavorable survival outcomes. Further studies are needed to confirm the extent to which our findings reflect the insufficient cancer care for older patients and improve the clinical outcomes of this population. Citation Format: Zhuoyang Zhao, Jianru Wang, Jinxin Lin, Shunlun Chen, Xiaolin Wang, Meijin Huang, Yanxin Luo, Huichuan Yu. Comprehensive characterization of rectal cancer reveals less cancer treatment with worse nutritional status and more comorbidities in the older patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5179.