Abstract 4206: The impact of two decades of multidisciplinary efforts to reduce the risk of recurrence from colorectal cancer - a Danish population-based registry-study
Authors: Nors Jesper , Gotschalck Kaare A. , Erichsen Rune , Iversen Lene H. , Andersen Claus L. 
Published: April 2023

Abstract
Purpose: Over the last two decades, several initiatives have aimed at reducing risk of recurrence in patients operated for non-metastatic colorectal cancer (CRC). The focus has been on improving treatment in a multidisciplinary setting and implementing a population-based screening program. However, the combined impact of these initiatives on the risk of recurrence is not well described. Therefore, the primary aim of this study was to determine and compare recurrence rates for three calendar periods 2004-2008, 2009-2013, and 2014-2019 (after implementation of screening) in CRC. Material and Methods: Patients undergoing surgery for UICC TNM stage I-III CRC in the period 2004 to 2019 were included. All patients were identified using the nationwide clinical quality database DCCG, and hereafter linked with data from the Danish Cancer Registry, the Danish National Registry of Patients, and the Danish Pathology Registry. Recurrence status was determined using a validated algorithm defining recurrence based on diagnosis codes of local recurrence or metastases, the receipt of chemotherapy, or a pathological tissue assessment code of recurrence. The algorithm has shown a positive predictive value of 94% and a negative predictive value of 99%. Cumulative risk of recurrence and relapse-free survival (RFS) was reported by grouping the patients in calendar periods.
Results: Of 33,470 stage I-III patients, 7,002 developed recurrence within 5 years after primary surgery (incidence rate = 60.4 per 1,000 person years, 95% CI: 59-61.8) with highest incidence among rectal cancer patients. The 5-year cumulative incidence of recurrence decreased for both colon cancers (2004-2009: 26% (95% CI: 25-27%); 2009-2013: 21% (95% CI: 20-22%); 2014-2019: 15% (95% CI: 14-16%)) and rectal cancers (2004-2009: 30% (95% CI: 29-32%); 2009-2013: 25% (95% CI: 24-27%); 2014-2019: 19% (95% CI: 18-20%)). The same pattern was found within each of stages I, II and III when stratifying by the three calendar periods. Screening-detected (SD) patients had lower risk of recurrence when compared to non-screening detected patients. The 5-year cumulative incidence of recurrence remained lower for 2014-2019 compared to previous calendar periods when excluding SD patients. Adjusted RFS improved significantly from 2004-2008 (reference) to 2014-2019 for colon cancer patients across all UICC stages; I) HR=0.49 (95%CI: 0.42-0.57), II) HR=0.56 (0.51-0.62) and III) HR=0.67 (0.62-0.73). The same pattern was seen for rectal cancer patients with HR=0.50 (0.42-0.60), HR=0.60 (0.52-0.69) and HR=0.67 (0.60-0.75) for stage I, II and III, respectively.
Conclusion: The national multidisciplinary initiatives to improve the outcome of CRC within the past two decades have borne fruit, as reflected by significant reductions in CRC recurrence risk and prolonged RFS observed for Danish stage I-III CRC patients.
Citation Format: Jesper Nors, Kaare A. Gotschalck, Rune Erichsen, Lene H. Iversen, Claus L. Andersen. The impact of two decades of multidisciplinary efforts to reduce the risk of recurrence from colorectal cancer - a Danish population-based registry-study. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4206.