Patients with locally advanced rectal cancer will receive biopsy before the standard treatment of neoadjuvant chemoradiation. The investigators are going to establish organoids model from the pre-treatment biopsies and expose organoids to irradiation and the same chemotherapy drugs. The sensitivity of irradiation and chemotherapy drugs will be tested in the organoids model. Here, the investigators will launch the observational clinical trial to validate whether the organoids could predict the clinical outcome in locally advanced rectal cancer patients underwent neoadjuvant chemoradiation.

Inclusion Criteria:

• pathological confirmed adenocarcinoma
• clinical stage T3-4 and/or N+
• the distance from anal verge less than 12 cm
• without distance metastases
• KPS >=70
• without previous anti-cancer therapy
• sign the inform consent

Exclusion Criteria:

• pregnancy or breast-feeding women
• serious medical illness
• baseline blood and biochemical indicators do not meet the following criteria: neutrophils≥1.5×10^9/L, Hb≥90g/L, PLT≥100×10^9/L, ALT/AST ≤2.5 ULN, Cr≤ 1 ULN

Patients with locally advanced rectal cancer will receive neoadjuvant chemoradiation. The radiation procedure and concurrent chemotherapy drugs will base on clinical practice.