All patients are planned to receive radical concurrent chemoradiotherapy. Intensity modulated radiotherapy (IMRT) will be used for external irradiation, with a dose of 45-50.4Gy /25-28 fractions. Combined three-dimensional intracavitary/interstitial (IC/IS) brachytherapy was applied. The preferred dose fraction plan is 6Gy*5 fractions, or 7Gy*4 fractions. Whether to adopt supplement radiotherapy can be decided by the tumor regression. Cisplatin 40 mg/m2 is recommended as the first choice for concurrent chemotherapy, and TP or TC can also be considered. Single-drug weekly therapy should be completed for at least 3 cycles, and combined 3-week regimen should be completed for at least 1 cycle.~Experimental group: from three days before radiotherapy to one week after radiotherapy, Kang Fu Pen (recombinant human superoxide dismutase) retention enema, 50ml/ time, once every other day. When rectal mucosa II degree reactions (NCI-CTCAE 5.0) occur, it is changed to 1 day/time until 1 week after mucosal remission.~Control group: 3 days before radiotherapy to the end of radiotherapy, no drug retention enema was used.
A total of 520 cases will be randomly divided into Kang Fu Pen (liquid dressing) enema intervention group (experimental group) and non-enema intervention group (control group), according to the ratio of 1:1.