Implications of Rectal Cancer Radiotherapy on the Immune Microenvironment: Allies and Foes to Therapy Resistance and Patients’ Outcome

1. Introduction Colorectal cancer (CRC) represents the third most diagnosed cancer and the second leading cause of cancer mortality for both sexes combined, comprising approximately 1 in 10 cancer cases and deaths worldwide in 2020 [1]. While the incidence of CRC for ≥50 year-old adults showed a favorable trend in recent years, the incidence recently increased in the group of young adults (<50 years-old) in multiple high-income countries [1,2,3,4].