The purpose of this study is to determine the role of endoscopic ultrasound measurement of the primary tumor maximum diameter changes in absolute / relative values in predicting the tumor regression after concurrent chemoradiotherapy for rectal cancer.

We use endoscopic ultrasound to measure the primary tumor maximum diameter changes to predict the tumor regression after concurrent chemoradiotherapy for rectal cancer

Inclusion Criteria:

• pathologically confirmed rectal cancer, preoperative stage II / III (T3-4N0 or T1-4N + M0).
• tumor distance from anus less than 12 cm.
• KPS score not less than 70
• can be tolerated chemotherapy and radiotherapy.
• pelvic who had no history of radiation therapy.
• Non-allergic history of fluorouracil or platinum-based chemotherapy drugs.
• a full understanding of the study, the ability to complete all of the treatment plan, follow up the conditions and sign the informed consent.

Exclusion Criteria:

• other malignancy (past or at the same time), does not include curable non-melanoma skin cancer and cervical carcinoma in situ; does not include resectable primary colon cancer (synchronous or metachronous).
• pregnant or lactating patients.
• fertility but did not use contraceptive measures.
• existing active infection.
• merge serious complications, can not tolerate the treatment, such as 6 months of myocardial infarction, mental illness, uncontrollable diabetes or uncontrollable hypertension or hypotension.
• concurrent treatment with other anticancer drugs.
• can not complete treatment or follow-up.

Local advanced rectal cancer