The study evaluates the associations between peak and valley concentrations of SN-38 with the efficacy and adverse effects of advanced rectal cancer patients carrying genotype (TA) 6 /(TA) 6 or (TA) 6 /(TA) 7 after neoadjuvant chemoradiotherapy with CPT-11.All participants will be scheduled to receive surgery 6-8 weeks after the completion of CRT. The primary end point are toxicity and pCR rate.

Inclusion Criteria:

• pathological confirmed adenocarcinoma
• clinical stage T3-4 and/or N+
• the distance from anal verge less than 12 cm
• without distance metastases
• performance status score: 0~1
• UGT1A1*28 6/6 or 6/7
• 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
• DPD deficiency
• UGT1A1*28 7/7