CGA Guided Ultrafractionated RT and Systemic Treatment in Elderly or Frail Patients with Inoperable Localized CRC

This is a prospective, multicentre, cohort study. For cohort 1, experimental cohort, older or Frail patients with inoperable localized colorectal cancer will receive Ultrafractionated Radiotherapy (RT) and Comprehensive Geriatric Assessment (CGA) Guided systemic treatment. All patients will receive Ultrafractionated RT and PD-1 antibody. Furthermore, CGA will assess all patients and classify them into Frail, Vulnerabe, or Fit. Frail patients will receive Best Supportive Care (BSC); Vulnerabe patients will receive Fluorouracil/Raltitrexed and BSC; Fit patients will receive Fluorouracil/Raltitrexed, Oxaliplatin/Irinotecan, and BSC. For cohort 2, external control from real word, data of patients with the same baseline characteristics from the same period and the same institute will be prospectively collected. The primary endpoint is complete response (CR, pathological complete response \[pCR\] plus clinical complete response \[cCR\]) rate. The secondary endpoints include the grade 3-4 acute adverse effects rate, anal preservation rate, 1-year DFS rate, 1-year DSS rate, 1-year OS rate etc.