The difference between rectal cancer lllc and lllb is mainly manifested in the fact that the invasion range of rectal cancer lesions in the two stages is different, the five-year survival rate level of patients is different, and the therapeutic measures taken are also different. 1. Stage lllc of rectal cancer indicates that the lesion has invaded the tissues and organs around the rectum and the number of regional lymph node metastasis is more than that of patients with lllb, while patients with Stage IIIb generally have not yet had peripheral tissue dissemination. 2. There is a difference in the level of five-year survival rate between rectal cancer patients with lllc and lllb, which is generally lower in patients with stage IIIc than those with stage IIIb. 3. There is a difference in the treatment plan adopted. Generally, most patients with stage IIIc rectal cancer are recommended to be given simultaneous radiotherapy before surgery. While some patients with stage IIIb can undergo radical surgery first and then be given adjuvant radiotherapy after surgery.