Between January 1, 2020, and January 1, 2022, 51 male patients with very low (≤ 5 cm from the anal verge) rectal adenocarcinoma were referred for operative treatment. Based on our previous experience and published literature, patients who met the following inclusion criteria were considered for laparoscopic CPSP: (1) the tumor involving was less than 1/3 of the rectal circumference; (2) patient was younger than 70 years old; (3) the American Society of Anesthesiologists (ASA) classification of patient was less than 3; (4) patient had a strong desire to preserve the anus and undergo CPSP. The exclusion criteria were as follows: (1) conversion to Miles’ surgery; (2) R2 resection; (3) total or partial pelvic exenteration; and (4) the use of drugs that could affect defecation function. A total of 25 patients were found to be suitable for CPSP and are the basis of this study ( Figure 1 ). All patients provided informed consent. Demographic information, comorbidities, and the medical history of the participants were collected. The study was registered in the Chinese Clinical Trial Registry under the registration number ChiCTR2100052094 and approved by the Ethics Committee of Peking Union Medical College Hospital (Ethics review approval No. JS-3361).

The sigmoid colon was initially mobilized, the inferior mesenteric artery was ligated at its origin, and the autonomic nerves were carefully preserved. The rectum was mobilized according to the principle of total mesorectal excision (TME) until it reached the entrance of the intersphincteric space. The conformal distal incision line was designed according to the location and size of the tumor. The aim was to preserve as much of the lower rectum, dentate line and internal anal sphincter on the side opposite the tumor as possible ( Figure 2 ). The angle between the cutting line and the dentate line was approximately 45°. The distal dissection line was made at least 1 cm below the inferior tumor margin under direct vision. The intersphincteric space was left undisturbed as much as possible to prevent injury to the numerous nerve fibers contained therein. End-to-end anastomosis was performed with a 25 mm circular stapler (CDH25, Johnson & Johnson, USA) under laparoscopy. The stapler was inserted as high up in the rectal stump as possible and tiled to the tumor side. The aim was to make the anastomosis on the rectal wall on the opposite side and to try to keep the dentate line and internal anal sphincter unbroken.

Temporary ileostomy was routinely performed and restored approximately 6 months later if there was no significant anastomotic stricture or anal dysfunction. The anastomotic status could be assessed by endoscopy or gastrointestinal contrast examination. Inject the vascular contrast agent (Omnipaque) mixed with 100ml of saline through a silicone tube (or catheter) into the colon 20cm above the colorectal (or coloanal) anastomosis, and then a standing X-ray examination or CT scan was performed. Anal function can also be evaluated by injecting 100ml saline into the colon above anastomosis. The patient’s health status is fully recovered to baseline, and inflammation has subsided with softening of adhesions a few months after surgery. Then the ileostomy was restored.

The following surgery-related information was collected: blood loss, operation duration, postoperative hospital stay duration, tumor size, distance from the anal verge, distal resection margin length, pathological T stage, pathological N stage, and tumor differentiation status. Patients with pathological stage III or stage II tumors with high-risk features received the postoperative CapeOx or mFOLFOX6 regimen as adjuvant chemotherapy. Postoperative radiotherapy was performed in patients who had not received preoperative radiotherapy according to the following criteria: (1) pathological result ≥ N1b or circumferential resection margin (CRM) positive; (2) T3 or T4 disease; and (3) distal margin too short (usually less than 0.3 cm).

Bowel dysfunction of patients was assessed via the low anterior resection syndrome (LARS) score questionnaire. LARS is defined by at least one of the following symptoms resulting in at least one of the following consequences that occur after a sphincter-sparing resection of the rectum (3). The symptoms include unpredictable bowel function, altered stool consistency, increased stool frequency, repeated painful stools, emptying difficulties, urgency, incontinence and soiling. The LARS questionnaire consists of 5 items: incontinence for flatus and liquid stools, defecation frequency, stool clustering, and urgency (4). Each item was graded from 3 to 16 points. The total score ranges from 0 to 42, and a lower score indicates better defecation function: no LARS (0-20), minor LARS (21-29), and major LARS (30-42).

The EORTC-QLQ-CR38 questionnaire survey was also conducted before and after surgery. The EORTC-QLQ-C30 questionnaire is specific for colorectal cancer patients (5). The EORTC QLQ-C30 questionnaire includes 15 items: physical function (5 questions), role function (2 questions), emotional function (4 questions), cognitive function (2 questions), social function (2 questions), global health (2 questions), fatigue (3 questions), nausea and vomiting (2 questions), pain (2 questions), dyspnea (2 questions), insomnia (1 question), appetite loss (1 question), constipation (1 question), diarrhea (1 question), and financial difficulties (1 question). Each question was graded from 0 to 4 points. The raw score was then standardized to range from 0 to 100. A lower score in the functional domain indicates worse function, and a lower score in the symptom domain indicates better symptoms.

Each patient underwent standard follow-up at the outpatient department from the first month after surgery. Tumor relapse was screened for with serum tumor markers and CT examination of the chest, abdomen, and pelvis every 6 months during the first 2 years. Moreover, assessments of defecation function and QoL were conducted at the outpatient department or via telephone.

The endpoint of the study is 2 years after CPSP. The second endpoint is that the patient died because of rectal cancer.

Continuous variables are presented as the means ± standard deviations and were analyzed with paired t tests to compare the values before and after surgery. Categorical variables are presented as numbers (percentages) and were analyzed with the chi-square test or Fisher’s exact test. A two-sided P value of less than 0.05 was considered statistically significant. Statistical analyses were performed with SPSS for Windows, version 20.0 (SPSS, Chicago, IL, USA). The sample size was calculated using G Power 3.1.9.7 (Universität Düsseldorf), with the α err prob of 0.05 and the power (1-β err prob) of 0.95, then the calculated sample size was 15.

Between January 1, 2020, and January 1, 2022, a total of 25 very low rectal cancer patients were enrolled in the study. Two patients were excluded because they were found to have abdominal metastases during the operation, 1 patient underwent conversion to Mile’s surgery, and 1 patient was lost to follow-up. Ultimately, 21 patients who underwent CPSP were followed up. The demographic characteristics of the patients are summarized in Table 1 .

The average age of the patients was 56.7 years, and their body mass index was 24.5 ± 3.1 kg/m². The tumors were 1.9 ± 0.6 cm in size; 85.7% of them were classified as T2 or T3, 71.4% of them were distributed on the lateral or posterior wall, and the distance between the tumor distal margin of the tumor and the anal verge was 4.8 ± 0.5 cm. A total of 66.7% of the patients had positive local lymph node metastasis on imaging. A total of 71.4% of the patients accepted the chemotherapy regimen with Xelox, and 66.7% of the patients accepted treatment with 45 Gy radiation.

The operative duration was 121.7 ± 28.3 minutes, and the blood loss volume was 43.3 ± 27.4 ml. Although preventive stoma formation was performed, 1 patient (4.8%) experienced anastomotic leakage. One patient (4.8%) experienced urine retention. According to the Clavien-Dindo classification, 2 patients (9.5%) were classified as having Grade II complications. The postoperative hospital stay duration was 7.1 ± 1.8 days (Table 2).

The margin clearance of the resected specimen was given special attention. The circumferential resection margin was negative, and the mesorectum was complete. The distance between the incisal margin and distal tumor margin was 1.1 ± 0.6 cm. The postoperative pathological results revealed that the main proportion of tumors were moderately differentiated (57.1%) ( Table 3 ). A total of 61.9% of the tumors were classified as T1 or T2, and 85.7% of the patients were found to have local lymph nodes that were negative for metastasis.

Of the 22 patients who were followed up, 21 patients (95.5%) responded to our interviews. All patients were followed up for more than 2 years. The follow-up period was 2.7 ± 0.5 years. Among them, 7 patients were followed up for more than 3 years. The LARS score significantly increased from 4.1 ± 2.8 before surgery to 19.1 ± 6.0 at the 1^st year after surgery (P < 0.001), and then reduced to 13.1 ± 4.2 at the 2^nd year after surgery (P < 0.001, Table 4 ). The quality of life score of patients also decreased from 74.2 ± 11.2 before surgery to 61.1 ± 9.6 at the 1^st year after surgery (P < 0.001) and then rose to 80.6 ± 11.9 at the 2^nd year after surgery (P = 0.029, Figure 3 ). The subscales physical functioning (P < 0.001), role functioning (P < 0.001), emotional functioning (P < 0.001), cognitive functioning (P < 0.001), social functioning (P < 0.001), fatigue (P < 0.001), nausea/vomit (P < 0.001), dyspnea (P < 0.001), sleep (P < 0.001), appetite (P < 0.001) and diarrhea (P < 0.001) subscale scores also significantly differed during the 2-year follow-up period. However, the constipation (P = 0.31), pain (P = 0.18) and financial difficulties (P = 0.14) subscale scores were not significantly different before surgery and after surgery.

Moreover, at the 2^nd year after surgery, physical function was not significantly different from that before surgery (P = 0.51). The subscales scores for role functioning, emotional functioning (P < 0.001), cognitive functioning (P < 0.001), social functioning (P < 0.001), fatigue (P < 0.001), nausea/vomit (P < 0.001), dyspnea (P < 0.001), sleep (P < 0.001), appetite (P < 0.001) and diarrhea (P < 0.001) improved 2 years after surgery.

During the 2-years follow-up period at the outpatient department, no rectal tumor relapse was found in these patients, although 2 patients (9.5%) experienced suspected local lymph node metastasis recurrence.