Comparison of risk factors, treatment strategy, and outcomes of early- vs. older-onset colorectal cancer within the prospective ColoCare study.

95 Background: The incidence of colorectal cancer among young adults aged 20-49 has continually increased in recent decades. Early-onset colorectal cancer (EOCRC) patients are more likely to be diagnosed at a more advanced stage of disease, have hereditary cancer syndromes, and have different molecular pathological features of disease than later-onset patients. Herein we compare the risk factors, treatment approaches, and responses to treatment of early-onset versus later-onset colorectal cancer within. Methods: The ColoCare Study is a prospective cohort enrolling individuals diagnosed with primary colorectal cancer at six different cancer centers in the United States and one in Germany. Serial questionnaires assess demographic characteristics and symptoms experienced prior to diagnosis, while clinical characteristics (including staging, pathology, treatments given) are abstracted from medical records. Restricting to patients with available age and stage, patients diagnosed <50 years old were labeled as “early-onset” and ≥50yo as “later-onset.” Associations between patient age and characteristics of interest were tested using Fisher’s Exact Test for count data. Results: Of the3,173 patients included in this analysis, 78% were later-onset (mean: 65 years) and 22% were early-onset (mean: 42 years). Demographic data was comparable between the two groups, with 43% being female. Though similar rates of ever alcohol use were seen between the two groups, early-onset patients reported consuming fewer weekly alcoholic beverages than later-onset patients (mean (standard deviation) of 5.5 (6.6) vs. 8.4 (9.3)). Early-onset patients were less likely to have ever smoked tobacco (38% vs 51%, p<0.001) and had lower rates of obesity (27% vs 31%) or overweight (34% vs 40%) than later-onset patients (p<0.001). For stage II/III disease, early-onset patients were more likely to have received chemotherapy and/or radiation treatment compared to later-onset patients (87% vs 70%, p<0.001), though both groups had similar rates of surgery. Despite this, younger patients did not appear to experience better outcomes, with 21% of younger patients experiencing a recurrence or new metastasis during follow-up versus 20% of later-onset patients. Conclusions: The risingincidence of colorectal cancer in early-onset patients does not appear to be explained by traditional risk factors such as alcohol use, tobacco use, or high BMI. Early-onset patients are more likely to receive chemotherapy or radiation, but observed outcomes are notably poorer compared to later-onset patients. Further statistical analysis on specifics of treatments by stage is ongoing.