Neoadjuvant Chemoradiotherapy in Locally Advanced and Locally Recurrent Colon Cancer

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.

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.

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.

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.