[Correlation between pelvic relapses of rectal cancer after radical and R0 resection: A regression model-based analysis].

To propose a new staging system for presacral recurrence of rectal cancer and explore the factors influencing radical resection of such recurrences based on this staging system. In this retrospective observational study, clinical data of 51 patients with presacral recurrence of rectal cancer who had undergone surgical treatment in the Department of Gastrointestinal Surgery, Peking University People's Hospital between January 2008 and September 2022 were collected. Inclusion criteria were as follows: (1) primary rectal cancer without distant metastasis that had been radically resected; (2) pre-sacral recurrence of rectal cancer confirmed by multi-disciplinary team assessment based on CT, MRI, positron emission tomography, physical examination, surgical exploration, and pathological examination of biopsy tissue in some cases; and (3) complete inpatient, outpatient and follow-up data. The patients were allocated to radical resection and non-radical resection groups according to postoperative pathological findings. The study included: (1) classification of pre-sacral recurrence of rectal cancer according to its anatomical characteristics as follows: Type I: no involvement of the sacrum; Type II: involvement of the low sacrum, but no other sites; Type III: involvement of the high sacrum, but no other sites; and Type IV: involvement of the sacrum and other sites. (2) Assessment of postoperative presacral recurrence, overall survival from surgery to recurrence, and duration of disease-free survival. (3) Analysis of factors affecting radical resection of pre-sacral recurrence of rectal cancer. Non-normally distributed measures are expressed as median (range). The Mann-Whitney test was used for comparison between groups. The median follow-up was 25 (2-96) months with a 100% follow-up rate. The rate of metachronic distant metastasis was significantly lower in the radical resection than in the non-radical resection group (24.1% [7/29] vs. 54.5% [12/22], χ=8.333, =0.026). Postoperative disease-free survival was longer in the radical resection group (32.7 months [3.0-63.0] vs. 16.1 [1.0-41.0], =8.907, =0.005). Overall survival was longer in the radical resection group (39.2 [3.0-66.0] months vs. 28.1 [1.0-52.0] months, =1.042, =0.354). According to univariate analysis, age, sex, distance between the tumor and anal verge, primary tumor pT stage, and primary tumor grading were not associated with achieving R0 resection of presacral recurrences of rectal cancer (all >0.05), whereas primary tumor pN stage, anatomic staging of presacral recurrence, and procedure for managing presacral recurrence were associated with rate of R0 resection (all <0.05). According to multifactorial analysis, the pathological stage of the primary tumor pN1-2 (OR=3.506, 95% CI: 1.089-11.291, =0.035), type of procedure (transabdominal resection: OR=29.250, 95% CI: 2.789 - 306.811, =0.005; combined abdominal perineal resection: OR=26.000, 95% CI: 2.219-304.702, =0.009), and anatomical stage of presacral recurrence (Type III: OR=16.000, 95% CI: 1.542 - 166.305, = 0.020; type IV: OR= 36.667, 95% CI: 3.261 - 412.258, = 0.004) were all independent risk factors for achieving radical resection of anterior sacral recurrence after rectal cancer surgery. Stage of presacral recurrences of rectal cancer is an independent predictor of achieving R0 resection. It is possible to predict whether radical resection can be achieved on the basis of the patient's medical history.