36 | wetenschapsdag 2023 Sessie 1b: Ticks, Checks and Balances 4 Auteurs E.G.M. van Geffen, J.A.M. Langhout, S.A. Hazen, T.C. Sluckin, G.L. Beets, R.G.H. Beets-Tan, W.A.A. Borstlap, K. Horsthuis, M.P.W. Intven, C.A.M. Marijnen, P.J. Tanis, M. Kusters, on behalf of the Dutch Snapshot Research Group Abstract titel Evaluation of clinical nature, treatment and oncological outcomes of locally recurrent rectal cancer over time: results from two national cross-sectional cohort studies Background In the Netherlands, there has been a reduction in radiotherapy usage for rectal cancer. While this decrease has not compromised oncological outcomes, neoadjuvant radiotherapy of the primary tumour is thought to affect the treatability of locally recurrent rectal cancer (LRRC). This study aims to evaluation the clinical nature, treatment and oncological outcomes of locally recurrent rectal cancer over time, by studying two national cross-sectional cohort studies. Methods All patients who underwent a total mesorectal excision in 2011 (n=2095) and 2016 (n=2855) for their primary tumour were included with a 4-year follow up and were merged from two nationwide cohort studies. Main outcomes included time to LRRC, synchronous metastases at time of LRRC diagnosis, intention of treatment and 2-year overall survival (OS) after LRRC. Results Between 2011 and 2016 a decrease in neoadjuvant (chemo) radiotherapy from 89.2% to 60.0% was observed. The 3-year LR rate was 5.5% in 2011 (n=95, median time to LRRC 18 months) compared to 6.8% in 2016 (n=173, p=0.121, median time to LRRC 16 months). No difference between synchronous metastases at time of LRRC diagnoses was found (26.2% in 2011; 32.5% in 2016, p=0.250). The intention of treatment shifted towards more curative treatment in 2016 compared to 2011 (38.0% vs 21.5%, p=0.003). Two-year OS after LRRC diagnoses increased from 30.4% in 2011 to 49.9% in 2016 (p=0.002), and from 47.5% to 78.7% when stratified for curative intent (p=0.006). Conclusion There was a significant increase in curative treatment and OS in 2016 compared to 2011. Factors that might contribute to this might be the decrease in neoadjuvant radiotherapy for the primary tumour, centralization of care and more extensive treatment options for LRRC and metastases.
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