A Randomized Phase 2 Study of Neoadjuvant Chemoradiaton Therapy With 5-Fluorouracil/Leucovorin or Irinotecan/S-1 in Patients With Locally Advanced Rectal Cancer

IS-based preoperative CRT did not increase pCR rate, but it did increase acute toxicities compared with standard 5-FU treatment. Therefore, further investigation is needed.