Abstract In order to preserve the anus, reduce recurrence, and prolong survival, neoadjuvant chemoradiotherapy has become an important part of rectal cancer treatment. This article discusses in detail the development and current status of neoadjuvant treatment for rectal cancer. The advantages and disadvantages of neoadjuvant radiotherapy and neoadjuvant chemoradiotherapy compared with surgery alone and adjuvant chemoradiotherapy are discussed. In 2004, nearly 40,500 new cases of rectal cancer were diagnosed in the United States [1], while in China, the incidence of rectal cancer is increasing year by year in major cities and is already trending to surpass gastric cancer as the second most prevalent gastrointestinal tumor. Surgical resection is the main method of rectal cancer treatment, and small superficial tumors can be cured by surgery alone. However, most rectal cancer patients are already in the middle and late stages when they are diagnosed, and often need to undergo extensive surgical resection or even full pelvic dissection, which is dangerous and has many postoperative complications. Most of the upper and middle rectal cancers can undergo anterior resection plus coloanal anastomosis, which preserves the anal sphincter and protects the pelvic plexus, reducing sexual function and genitourinary system complications. Treatment of lower segment rectal cancer: how to eradicate the tumor while preserving the anal sphincter is an important problem that is more difficult to solve clinically. Combined transabdominal perineal resection has been the standard procedure for rectal cancer within 6 cm from the anal verge, and although the tumor is better controlled, permanent fistula and genitourinary complications seriously affect the quality of life of patients. For superficial lower rectal cancer (T1 or T2), local resection is currently considered an alternative to combined transabdominal perineal resection, and both procedures are similar in terms of local control and overall survival. For rectal cancer with deep infiltration and/or lymph node involvement, and for lower segment rectal cancer in which the anus cannot be preserved, combined treatment has been widely used in order to preserve the anus, reduce recurrence, and prolong survival. In recent years, the treatment of rectal cancer has made breakthroughs with the emergence of new drugs and new treatment methods, and neoadjuvant chemoradiotherapy is being studied in depth. The following article will discuss in detail the development and status of neoadjuvant treatment for rectal cancer: neoadjuvant radiotherapy for rectal cancer: neoadjuvant radiotherapy for rectal cancer has been widely used. Theoretically, neoadjuvant radiotherapy has the following advantages: 1. to reduce the stage and shrink the tumor, so that locally advanced rectal cancer that cannot be radically resected can be radically resected; 2. to enable rectal cancer near the anus to be anus-preserving through radiotherapy; 3. for resectable rectal cancer, neoadjuvant radiotherapy preoperatively kills tumor cells to reduce the risk of tumor cell spread during surgery; 4. Preoperative radiotherapy is more effective in killing tumors because surgery destroys the local blood supply and decreases the oxygen content within the tumor, thus decreasing the sensitivity of postoperative radiotherapy. Regarding neoadjuvant radiotherapy, most of the current studies are retrospective meta-analyses. At least two studies in the data of the meta-analysis showed the benefit of preoperative radiotherapy [2,3]. The first study, including 14 randomized controlled trials published between 1975 and 1997 [2], had 6,426 patients, mostly with resectable rectal cancer, randomized to surgery alone or after neoadjuvant radiotherapy, with a significantly lower rate of local recurrence, overall survival (ratio [OR] 0.84, 95% confidence limits 0.72-0.98) and etiology in the neoadjuvant radiotherapy group specific survival (OR 0.71, 95% confidence limits 0.38-0.62) were improved. In another study, including 14 randomized controlled trials conducted before January 1987 with a total of 6350 patients, the neoadjuvant radiotherapy group had a significantly lower rate of positive lymph nodes at surgical resection (32% versus 38%), a significantly lower 5-year overall recurrence rate (46% versus 53%), and a significantly lower 5-year local recurrence rate (13% versus 22%) [3]. Compared to surgery alone, the neoadjuvant radiotherapy group was significantly less likely to die from rectal cancer (45% versus 50%), but 5-year overall survival was similar in both groups (64% versus 65%). Early mortality (within 1 year of treatment) was twice as high in the neoadjuvant radiotherapy group as in the surgery alone group (8% versus 4%). Technically, there have been four preoperative neoadjuvant radiotherapy methods: 1) preoperative low-dose radiotherapy; 2) preoperative moderate-dose radiotherapy: 34.5 Gy in 15 fractions of 2.3 Gy each; 3) preoperative short-course high-intensity radiotherapy: also known as Swedish radiotherapy, 5 fractions of 5 Gy each in one week, and surgery within one week after the completion of radiotherapy; 4) high-dose conventional fractionated radiotherapy: 1.8-2.0 Gy each, 5 times a week The total of 5-6 weeks, can be synchronized with chemotherapy and surgery 4-6 weeks after the end of radiotherapy. A number of clinical studies have concluded that: 1) preoperative low-dose radiotherapy does not improve local control and survival compared with surgery alone [4]; 2) preoperative radiotherapy at moderate doses reduces the local recurrence rate but does not prolong survival compared with surgery alone [5]. Therefore, preoperative radiotherapy at low and medium doses is no longer used. The following discussion focuses on preoperative short-course high-intensity radiotherapy and high-dose conventional fractionated radiotherapy. Short-course high-intensity neoadjuvant radiotherapy: A study on rectal cancer was conducted in Sweden between 1987 and 1990, which was the first randomized study on neoadjuvant radiotherapy. 1168 cases of resectable rectal cancer were enrolled in two groups: one group was operated on alone, and the other group was treated with 25 Gy/min 5 times preoperative radiotherapy and operated within one week after radiotherapy; the local recurrence rate was significantly reduced in the preoperative radiotherapy group.