Improvement In Colorectal Cancer Outcomes Over Time is Limited To Patients With Left-Sided Disease

Purpose: Incidence and mortality of colorectal cancer (CRC) declined over the last decades. However, survival depends on the primary tumor location. It is unknown if all progress in outcomes vary depending on left-sided (LCRC) versus right sided (RCC) colorectal cancer. We compare incidence and mortality rates over time according to the primary tumor location. Methods: Data from the Austrian National Cancer Registry spanning from 1983 to 2018 were used to calculate annual incidence and mortality rates and survival stratified by primary tumor localization and stage. Joinpoint regression with linear regression models were used on different subgroups to identify significant changes of incidence- and mortality slopes.Results: A total of 168,260 (incidence-data set) and 87,355 cases (mortality data-set) were identified. Survival of disseminated RCC was worse compared to LCRC (HR 1.14; CI 1.106 – 1.169). Total and LCRC incidence- and mortality-rates declined steadily over time, whereas the rates of RCC did not. Incidence of disseminated RCC declined significantly less (slope -0.07; CI -0.086; -0.055) than in LCRC (slope -0.159; CI -0.183; -0.136); mortality rate of RCC was unchanged over time. Incidence and mortality of localized RCC remained unchanged over time, whereas both rates declined independently of stage in LCRC. Conclusion: Colorectal cancer outcomes during the last 35 years have preferentially improved in LCRC but not in RCC, indicating that the progress made is limited to LCRC. It is necessary to define RCC as a distinct form of CRC and to focus on specific strategies for its early detection and treatment.