Common use of Study Population Clause in Contracts

Study Population. All patients who underwent surgery for first primary colon cancer between January the 1, 2013 and December the 31, 2019, and registered in the DCRA were potentially eligible for this study (N=52,035) (Figure 1). For the purpose of this study, the following patients were excluded: patients with a synchronous colorectal carcinoma (N=1,770), patients who underwent emergency surgery (N=6,806), underwent a local excision (N=39), patients in whom no primary anastomosis was constructed (N=2,659), patients with a prior stoma of any type as bridge to surgery which was not reversed during the elective colectomy or patients with a stoma of any type constructed during elective colectomy (N=1,178), patients with missing data on AL (N=3), and proctocolectomy (N=15) were excluded. After exclusion, a total of 39,565 patients were included in the study. E l e c t i v ec ca on lco enr s u r g p r i m a r y a n a s t o m o s i s N = 3 9 , 5 6 5 T o tnau lm b ecor loocfna n c e r p a t i who u n d e r swu re gnet r y -(202 10 91 )3 N = 5 2 , 0 3 5 E x c l u s i o n : - S y n c h r o n o u s C R C , N = 1 , 7 7 0 - E m e r g e n c y s e t t i n g , N = 6 , 8 0 6 - L o c a l e x c i s i o n , N = 3 9 - N o p r i m a r y a n a s t o m o s i s , N = 2 , 6 5 9 - M i s s i n g c a s e s f o r A L , N = 3 - P r o c t o c o l e c t o m y , N = 1 5 Figure 1 presents the flowchart of the present study. Synchronous CRC: synchronous colorectal cancer, AL: anastomotic leakage. The overall AL rate was 4.8% and baseline characteristics are displayed in Table 1. Compared to patients without AL, thosewith ALwere more frequently male (62.5% vs. 52.2%, p<0.001), obese (BMI ≥30 kg/m2 22.7% vs. 19.9%, p=0.009), less healthy (ASA III+ 31.7% vs. 24.8%, p<0.001; CCI II+ 32.7% vs. 28.0%, p<0.001), more often presented with tumor−related complications such as anemia or peritumoral abscess (32.7% vs. 27.4%, p=0.006) and had a more advanced tumor stage (T4 13.5% vs. 10.0%, p<0.001 and M1 11.0% vs. 7.4%, p<0.001). Regarding treatment characteristics, these patients more often received neoadjuvant chemotherapy (3.1% vs.1.6%, p<0.001), more often underwent an open resection (23.8% vs. 16.5%, p<0.001), a multivisceral resection (11.5% vs. 6.5%, p<0.001) or an additional resection for metastasis (5.5% vs. 2.8%, p<0.001). The total number of patients treated at low−volume hospitals was 5,564, which was 7,454 for low-intermediate volume hospitals, 8,163 for intermediate-high volume hospitals, and 18,384 for high volume hospitals. The highest AL rate was found for low volume hospitals (6.0%), which was significantly higher if compared to the other volume categories (low−intermediate volume hospitals 4.3%, intermediate−high volume hospitals 4.7%, high−volume hospitals 4.7%, p<0.001). Age ≥75 13,526 (35.9) 698 (36.6) 0.565 Missing 6 0 Sex Male 19,642 (52.2) 1,191 (62.5) <0.001 Missing 11 0 BMI <18.5 1,103 (2.9) 51 (2.7) 0.009 18.5−30.0 29,054 (77.2) 1,421 (74.5) ≥30 7,484 (19.9) 433 (22.7) Missing 17 2 ASA score III+ 9,348 (24.8) 604 (31.7) <0.001 Missing 9 0 CCI II+ 10,619 (28.0) 626 (32.7) <0.001 Tumor complicationA 10,316 (27.4) 579 (32.7) 0.006 Missing 64 1 Neoadjuvant chemotherapy 610 (1.6) 60 (3.1) <0.001 Missing 848 45 Approach Open 6,209 (16.5) 456 (23.8) <0.001 LaparoscopicB 31,008 (82.3) 1,432 (75.1) Missing 441 23 Type of resection Right hemicolectomy 19,507 (51.8) 823 (43.2) <0.001 Transversectomy 813 (2.2) 65 (3.4) Left hemicolectomy 4,106 (10.9) 295 (15.5) Subtotal colectomy 318 (0.8) 58 (3.0) Sigmoid resection 12,729 (33.8) 650 (34.1) Missing 185 16 Stoma as bridge to surgery No, stoma created as bridge to surgery 37,325 (99.1) 1,884 (98.8) 0.184 Yes, reversed during elective colectomy 333 (0.9) 23 (1.2) Multivisceral resection 2,461 (6.5) 219 (11.5) <0.001 Missing 15 0 Additional resection for 1,041 (2.8) 105 (5.5) <0.001 metastases Missing 28 1 T stage T1−2 13,980 (37.1) 599 (31.4) <0.001 T3 19,726 (52.4) 1,046 (54.9) T4 3,766 (10.0) 257 (13.5) Missing 186 5 N stage N0 25,307 (67.2) 1,261 (66.1) 0.326 N1−2 12,235 (32.5) 641 (33.6) Missing 116 5 M stage M- 34,859 (92.6) 1,698 (89.0) <0.001 M1 2,799 (7.4) 209 (11.0) Table 1: Study population characteristics of patients who underwent colon cancer resection, stratified for anastomotic leakage (non−anastomotic leakage (non−AL) versus anastomotic leakage (AL)). A: tumor complications are preoperative complications caused by the tumor, including peri−tumoral abscess, anemia, perforation, obstruction/ileus. B: laparoscopic procedures include conventional and robot− assisted laparoscopic procedures. Missing values less than 10% are only presented as absolute numbers. A Xxxxxxx Xxx-square test was used to calculate the p value. The AL rate differed significantly among the different index procedures. The lowest AL rate was found for patients who underwent a right hemicolectomy (4.0%), followed by sigmoid resection (4.9%), left hemicolectomy (6.7%), transversectomy (7.4%), and a subtotal colectomy (15.4%) (p<0.001) (Figure 2A). Reinterventions were predominantly surgical, ranging from 81.2% for transversectomy to 92.4% for sigmoid resection (p<0.001) (Figure 2B). The median time to reoperation differed significantly among the index colectomies with the shortest time interval to reoperation for sigmoid resection (4 days, IQR 3−6), followed by hemicolectomy (both left and right: 6 days, IQR 4−9) and transversectomy (6 days, IQR 3−9), and the longest for subtotal colectomy (8 days, IQR 4−11) (p<0.001). Figure 3 demonstrates that most reoperations were performed on postoperative day 3−4 (N=156 for right hemicolectomy, N=65 for left hemicolectomy, N=240 for sigmoid resection, and N=10 for subtotal colectomy).