An appropriate cutoff of age and the impact of age on colorectal cancer outcomes remain unclear and need to be explored, particularly in China.
In total, 2460 colorectal cancer patients were studied retrospectively. All patients were divided into 6 groups according to their ages at the time of diagnosis: ≤30, 31 to 35, 36 to 40, 41 to 45, 46 to 50, and ≥50 years. A suitable cutoff age for defining young adult colorectal cancer was explored according to the distribution of survival in each group. Clinical characteristics and prognosis between the young adult group and the older group were then compared.
According to the survival curves for each group, 35 years old was considered a suitable cutoff age for defining young adult colorectal cancer. There were 140 (5.7%) and 2320 (94.3%) cases in the young adult and older groups, respectively. The proportion of stage III–IV tumors was significantly higher in the young adult group (69.3%) than in the older group (46.4%) (P = 0.000). The univariate analysis showed that the 5-year overall survival (OS) rate and the 10-year OS rate in the young adult group were 48.9% and 38.6%, respectively, whereas in the older group, they were 63.6% and 56.9%, respectively. The young adult group had a worse prognosis (P = 0.000). The multivariate analysis showed that age was not an independent prognostic factor (relative risk 0.787, P = 0.062). After adjusting for tumor stage, the hazard proportion of death in the young adult group increased by 27.6%, but this difference was not significant (P = 0.053). Stratified analyses showed that the young adults with stage IV tumors had a worse survival rate (P = 0.046).
Patients ≤35 years who were diagnosed with colorectal cancer had a worse prognosis because of a higher proportion of advanced stage tumors. When stage-to-stage analysis was performed, it was found that young adult colorectal cancer patients had a worse outcome only if they had stage IV tumors.