Impact of COVID-19 pandemic on diagnosis, staging, and outcomes of patients with earlyonset colorectal cancer.

15 Background: Although we seem to be recovering from COVID-19, we are now facing the long-term consequence of the pandemic on vulnerable subgroup of patients such as patients with early-onset colorectal cancer (EOCRC). We aim to study how the COVID-19 pandemic affected the diagnosis and clinic-pathological characteristics, treatment and outcomes of patients with EOCRC. Methods: This is an observational retrospective study including patients with EOCRC diagnosed between September 2016 and August 2021 at Hospital Universitario La Paz, Madrid, Spain. Two cohorts were stablished: before and after March 14, 2020, the day of the first lockdown in Spain. Results: A total of 1409 patients with CRC were included. Of those, 5,2% were EOCRC (n=75). Fifty-five (73%) and 20 (27%) were diagnosed pre, and post pandemic. The rate of EOCRC diagnosis per month was 1,8 and 1,1 in the pre and postpandemic group, respectively. Fifty percent of patients in the postpandemic group were diagnosed with metastatic disease, while only 29% had stage IV at diagnosis in the prepandemic subgroup (P = 0,09). High tumor budding, surgical margins affected, lymphovascular, and perineural invasion were also pathological features more observed in the postpandemic subgroup, although results are not statistically significant. The differences between both groups are depicted. After a median follow-up of 23 months (33 and 14 months in the pre and postpandemic group, respectively), 11 patients have died (15%). Median overall survival (OS) was not reached in either group. At 12 months, 94% and 89% of patients were alive in the pre and postpandemic group, respectively. Conclusions: COVID-19 has influenced the diagnosis and staging of patients with EOCRC. Long-term follow-up is needed to assess the survival in this population. The role of primary care in the diagnosis and early referral of these patients is, more than ever, crucial. [Table: see text]