Between January 2015 and July 2018, total 686 patients with low rectal cancer who met the incision criteria of rectal incision were enrolled in this study at gastrointestinal surgery department. Of these patients, 200 patients underwent RAS and 486 patients underwent LAS respectively. Preoperative clinical characteristics for the two groups are displayed in Table 1. The distance from the anal verge in the RAS group was significantly lower than LAS group (5.06±0.84 cm vs 5.66±0.53 cm, P＜0.001). No significant difference was observed in term of gender, age, ASA classification, NRS 2002 score, comorbidity (diabetes), level of serum hemoglobin, plasma albumin, serum CEA and CA199. Distribution of clinical T-stage, N-stage and TNM-stage, proportion undergoing preoperative neoadjuvant chemoradiotherapy were also similar between two groups. Besides, the total costs were higher in RAS group (53922±14290 ￥ vs 48522±14290 ￥, P＜0.001).
The intraoperative outcomes and recovery courses were shown in Table 2. Only 2 patients (0.4%) required conversion to open in the LAS group (one case with narrow pelvis and pelvic adhesions, one case with intraoperative bleeding). The operative time was significantly longer in RAS group (249±64 min vs 203±47 min, P＜0.001). The estimated intraoperative blood loss was significantly higher in the LAS group (95±33 ml vs 82±49 ml, P=0.001). A total of 8 patients (4%) required blood transfusion in the RAS group, and 18 patients (3.7%) in the LAS group (P＞0.05). But no significant difference was found between two groups. Temporary ileostomy was conducted in 129 patients (64.5%) in the RAS group and in 251 patients (51.6%) in the LAS group respectively (P＜0.05). No adverse events occurred in two groups during operation. The RAS group was with a shorter time of first flatus and liquid intake [2 (1,3) vs 3 (2,3), P＜0.0001; 3 (2,4) vs 4 (3,4), P＜0.0001, respectively]. The firstly leaving bed time in the RAS group was significantly shorter than LAS group [2 (2,3), vs 3 (2,3), P＜0.001]. The removal time of catheter was shorter in RAS group [4.9±1.2 vs 5.2±1.3, P=0.004]. Similarly, the same result of length of hospital stay was observed (9.5±4.6 days vs 11.3±5.9 days, P＜0.001). And there was no significant difference in terms of VAS score, the drainage of cube duration and total volume of drainage.
All of the postoperative complications were shown in Table 2 before discharge in two groups. Totally, 118 complications were occurred, as follows, 32 (16%) in RAS group, 86 (17.7%) in LAS group (P= 0.593). Among these complications, 1 patient (0.5%) died because of cardiovascular accident in RAS group, and 2 patients (0.4%) died in LAS group, with one died of cardiovascular accident, the other died of multiple organ failure as a result of anastomotic leakage (P＞0.05). The rate of postoperative urinary retention was higher in LAS group (4.1% vs 3.5%, P=0.706), but the difference was not statistically significant. And the type of complications was no significant difference between two groups. The Clavien-Dindo classification was used to classify the severity of all complications. And the distribution of severity showed not statistically significant difference between two groups (P＞0.05). The grade Ⅰ-Ⅱ of complications accounted for 81.25% of all complications in RAS group and 88.7% in the LAS. In addition, a total of 32 patients (4.7%) suffered from anastomotic leakage between two groups, which were treated with conservative treatment except for 6 patients, with 2 patients in the RAS group, and 4 patients in the LAS group (P＞0.05). 2 patients in LAS group and 1 patient in RAS group with postoperative ileus required second operation, and 1 patient with intra-abdominal abscess in RAS group experienced relaparotomy within 30 days after surgery.
The pathological results were also shown in Table 2. Median distal resection margins in the RAS group and LAS group were 1.4 cm (1.1, 1.9) and 1.6 cm (1, 2), respectively (P＜0.05). The involved circumferential margin (CRM) was confirmed in two patients in the LAS group (P＞0.05). The R0 resection achieved all cases excepted for 2 patients in LAS group. The tumor size, mean harvested lymph nodes, vascular invasion, nerve invasion, tumor deposit, the distribution of histologic differentiation and clinical TNM stage were similar in the two groups (all, P＞0.05).
Changes in the total IPSS score and Wexner score
Preoperative and postoperative changes in urinary function and bowel function were both shown in Table 3. A total of 169 patients (84.5%) in the RAS group received the assessment after surgery, and 404 patients (83.1%) in the LAS group. Preoperative IPSS scores between LAS and RAS showed no significant difference (P=0.088). The IPSS scores between two groups appreciably increased after postoperative 1 month (P＞0.05). The score decreased significantly after postoperative 3 months in the RAS group [RAS 5, (5,6) vs LAS 7(6~8), P＜0.001]. The difference continued 6 months after surgery between two groups (RAS, 5(4~6) vs LAS, 6(4,7), P＜0.001). At 2 years after surgery, 3 cases (1.7%) suffered from moderate urinary dysfunction in the RAS group, and 9 cases (2.2%) in the LAS group (P＞0.05).
Wexner score results showed increasing trend after surgery and decreased gradually in the recovery course similarly. The scores at 6 months after surgery for the RAS group were significantly lower than LAS group [RAS 0 (0.1) vs 1(1,3), P＜0.001]. The scores recovered approximately normal level at 12 months for the RAS group, but more than 12 months for the LAS group [RAS 0 (0,1) vs LAS 1 (0,1), P＜0.001].
Changes in total IIEF scores and FIFS scores
IIEF scores were analyzed for 121 male patients (RAS 46, LAS 75). Changes in total IIEF scores for male patients were showed in Table 3. The mean total IIEF scores at 6, 12 months after surgery for the RAS group were significantly higher than LAS group [RAS 38.5±4.5 vs LAS 34.5±5.8, P＜0.001; RAS 46.4±5.9 vs 41.0±5.6, P＜0.001, respectively]. At 24 months after surgery, 1 patient in the RAS group and 2 patients in the LAS group suffered from erectile dysfunction.
Total 75 female patients (RAS 20, LAS 55) participated in the assessment of sexual function. Total FIFS scores were also presented in Table 3. The results showed that the recovery of sexual function in the RAS group was accelerated significantly at 3 months after surgery than LAS group (RAS 16.6±3.7 vs LAS 14.2±2.5, P=0.003). And the mean total FIFS scores were significantly higher in the RAS group than LAS group at 6,12 months after surgery (all P ＜0.05).
The median follow-up was 53.2 months for the RAS group and 54.1 months for the LAS group respectively. OS and DFS at 1, 3, 5 years after surgery were similar between two groups. The Kaplan–Meier curve of OS and DFS was presented in Figs. 1, 2 respectively. A total of 69 patients (10.1%) suffered from distant metastases, including liver (n=34), pulmonary (n=34) and brain (n=1), with no significant difference between RAS group and LAS group. In addition, 19 patients (9.5%) in the RAS group and 50 patients (10.3%) in the LAS group were diagnosed with local recurrence around surgery position (P=0.883). Cox regression analyses presented in Table 4. indicated that the positive CRM, pT stage, positive lymph nodes (pN+) and age may be the significant predictors of OS after surgery. The DFS showed the similar results except for age.