U-shaped relationship of age at diagnosis and cancer-specific mortality in primary urachal adenocarcinoma: a cohort study

BACKGROUND: To examine the association between age at diagnosis and cancer-specific mortality (CSM) in primary urachal adenocarcinoma. METHODS: The data was obtained from the National Cancer Institute’s Surveillance, Epidemiology, and End Results program (SEER). A total of 393 patients were included in the study. Smooth curve fitting and two-piecewise Cox proportional hazards models were used to identify the nonlinearity between the age at initial diagnosis and cancer-specific survival rate. Survival time between different groups was compared using Kaplan-Meier survival curves and the log-rank test. RESULTS: Using smooth curve fitting we found that the relationship between age at diagnosis and cancer-specific survival takes on a U-shaped curve. The inflection point that we identified for the age at initial diagnosis was 60 years. The log-likelihood ratio test (P<0.05) indicated that the two-piecewise Cox regression model was more appropriate for fitting the correlation of age at diagnosis and CSM. The two-piecewise Cox regression model showed that when the age was <60 years, reduced risk of CSM was significantly associated with increased age (HR: 0.95, P=0.0002). Conversely, when age was >60 years, increased risk of CSM was significantly associated with increased age (HR: 1.05, P=0.0499). CONCLUSIONS: In summary, our study suggested that the relationship between age at diagnosis and cancer-specific survival is nonlinear, and takes on a U-shaped curve. Both younger and older age at initial diagnosis age were associated with increased CSM.