Prognosis and clinicopathological features of patients with early-onset and late-onset colorectal cancer with second primary malignancies

Background and AimThe risk of developing a second primary malignancy differs among colorectal cancer patients in different age groups. This study aimed to investigate the differences in prognosis and clinicopathological features of patients with early-onset colorectal cancer and late-onset colorectal cancer who developed second primary malignancies.MethodsThe study included 15 489 patients who underwent surgery for colorectal cancer at Fudan University Shanghai Cancer Center between January 2008 and December 2018. Data pertaining to these patients were derived from the database.ResultsA total of 680 (4.5%) patients subsequently developed a second primary malignancy. Considering death as a competing event, the 10-year cumulative risk of second primary malignancy for early-onset colorectal cancer was 5.3%, compared with 7.3% for late-onset colorectal cancer. Cox analysis showed that late-onset colorectal cancer, colon cancer, smaller tumor size, and fewer tumor nodules without residual lymph node structure, chemotherapy, and radiotherapy were independent risk factors for second primary malignancy. In our patient cohort, early-onset colorectal cancer was associated with better prognosis compared to late-onset colorectal cancer, for both overall survival and second primary malignancy-free survival. In addition, there was insufficient evidence that early-onset colorectal cancer also affected prognosis after the occurrence of second primary malignancies.ConclusionsThe risk of early-onset colorectal cancer subsequently developing second primary malignancy was significantly lower than late-onset colorectal cancer, and the second primary malignancies of early-onset colorectal cancer were more likely to be colorectal cancer. Overall survival and second primary malignancy-free survival of early-onset colorectal cancer were consistently better than late-onset colorectal cancer.