Clinical response

Clinical remission will be evaluated according to the World Health Organization (WHO) criteria, the Response Evaluation Criteria in Solid Tumors (RECIST) [14]. A pelvic MRI will be performed at the end of the 4 weeks of NACT to assess the response using the RECIST 1.1 criteria. The overall response will be determined using pelvic MRI 12 weeks after the completion of CCRT. MRI scans will all be reviewed at Ruijin Hospital and assessed by two radiologists blinded to the treatment option based on the RECIST 1.1 criteria. Further radiological assessments will be conducted as clinically indicated. The complete response (CR) is defined as the disappearance of all target lesions, and any pathological lymph nodes (whether target or nontarget) must have a reduction in the short axis to < 10 mm. Partial remission (PR) is defined as at least a 30% decrease in the sum of the diameters of the target lesions, taking as the reference of the baseline sum of the diameters. Progressive disease (PD) is defined as at least a 20% increase in the sum of the diameters of the target lesions, taking as the reference the of baseline sum of the diameters, with the smallest sum of increase at least 5 mm. In addition, a relative increase of more or new lesions is also considered progression. Stable disease (SD) is defined as neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD. Patients with CR or PR will be classified as clinical responders, and patients with stable disease and progression of disease will be defined as clinical nonresponders. If the two radiologists reached different conclusions, the results will be rechecked and discussed to reach a consensus.