Neoadjuvant Chemoradiotherapy in Locally Advanced and Locally Recurrent Colon Cancer.

Aims: While systemic management of high risk colon cancer is well addressed, advances in local management remain incremental. This study aims to identify a group of colon cancer patients where local management remains a challenge, and where intensifying local treatment with radiotherapy is potentially beneficial to minimise the risk of an R1 resection.

Materials and methods: The patients with select cT4 locally advanced primary colon (LAPC) (n = 40) and locally recurrent colon (LRC) (n = 48) adenocarcinomas who received neoadjuvant radiotherapy from 2005 to 2020 were studied. Radiotherapy prescription was 45-50.4 Gy in conventional fractionation. The estimated median follow-up time was 8.1 years and 6.3 years for the LAPC and LRC groups, respectively.

Results: The most common primary site was the sigmoid colon (n = 61). In the LAPC group, surgery was performed in 90% (n = 36), 81% (n = 29) of which were R0 resections, with pathologic downstaging occurring in 66.7% (n = 24). In the LRC group, surgery was possible in 79.2% (n = 38), 65.8% (n = 25) of which were R0 resections. For the LAPC group, 13% (n = 5) had local failures (hazard rate 3%, 95% CI 1-6%), 38% (n = 14) had any disease progression (hazard rate 9%; 95% CI 5-14), and 55% (n = 22) were alive at the end of the follow-up period (hazard rate 8%; 95% CI 5-13). For the LRC group, 35% (n = 17) had local failures (5-year local failure-free survival: 53%; 95% CI: 37-74), and 61% (n = 30) had any disease progression (5-year progression-free survival: 28%; 95% CI: 17%-48%). Five-year overall survival for the LRC group was 50% (95% CI: 37-68). There was no 30-day mortality.

Conclusion: Local management of high risk colon cancer remains a challenge. Future studies in neoadjuvant chemoradiation and systemic therapy, and staging methodology in identifying the high risk group are urgently needed.