Conditional Survival with Time of Overall Survival and Disease-free Survival for Mid or Low Locally Advanced Rectal Cancer

Abstract

Abstract Aim To evaluate the changes of conditional survival (CS) for mid or low locally advanced rectal cancer (LARC) and to determine how the prognostic factors affecting CS evolve over time. Methods We analyzed data of 1833 patients from two centers. Kaplan-Meier and multivariate Cox regression were used to calculate conditional disease-free survival (cDFS) and conditional overall survival (cOS). Multivariable Cox regression models were used to calculate proportional hazard ratios (HR) for the prediction of cDFS and cOS. Funding The 5-year OS and DFS estimates were 83.3% and 78.3%, respectively. Given a 1-, 2-, 3-, 4- and 5-year survivorship, the 5-year cOS rates increased to 83.7%, 85.0%, 85.8%, 89.1%, and 92.6%, respectively. Similarly, given a 1-, 2-, 3-, 4- and 5-year disease-free survivorship, the 5-year cDFS rates increased to 81.8%, 86.0%, 88.3%, 92.3%, and 94.6%, respectively. The impact of well-known prognostic factors on CS estimates relevance changed or even disappeared over time. Whereas distance to the anal verge (DTAV) and neoadjuvant rectal (NAR) score was the most stable and reliable prognostic factors for CS. Independent effects of NAR score (HRs 1.68, 1.85, 2.10, 1.99, 3.38, respectively) and DTAV (HRs 0.48, 0.52, 0.52, 0.47, 0.34, respectively) factors on cOS can be found, at all-time points including baseline, 1, 2, 3, and 4 years. Interestingly, a consistent independent effect of NAR (HRs 1.71, 1.89, 1.83, 1.84, 2.78, respectively) score on cDFS at baseline, 1, 2, 3, and 4 years survived, and DTAV (HRs 0.51, 0.61, 0.62, 0.45, respectively) on cDFS at survived for within 3 years. The stratified analysis revealed that the lower the DTAV or higher the NAR score, the lower the 5-year CS probability over the entire time after surgery, which supports the results of multifactorial Cox regression. Conclusions CS rates increase over time in LARC patients, especially in patients with long-term survival. Factors of influence may change with prolonged survival, DTAV and NAR score were persistent predictors of long-term prognosis.